Neurotransmitter Measurements

[RobinN]

Many diseases are associated with specific chemical alterations; these alterations are commonly called biomarkers and are routinely used to determine if a medical event or process will occur, is occurring, or has occurred. While they may be indirect, the interest in identifying chemical measurements that can be used as biomarkers is very high. This is especially true for conditions that currently do not have diagnostic biomarkers, such as mood and hyperactivity disorders. Chemicals like neurotransmitters, which change in a predictable manner and parallel the patient's clinical symptoms, have become valuable markers for medical processes within the body. (1)

Psychiatric disorders like depression or anxiety may be diagnosed based only on clinical signs and symptoms, but identifying imbalances in brain chemicals that are associated with the presence of the disorder can provide insights regarding possible prevention and treatment strategies that are not evident in the diagnosis alone. As the number of urinary neurotransmitters tested grows, the predictive value of neurotransmitter test panels will become more powerful and the ability to prevent disorders, improve treatment through early detection, and/or match or monitor treatments to the patient's condition, will improve.

http://www.encyclopedia.com/doc/1G1-140490462.html

As with many tests there are some that this this is not effective, and others that tend to swear by it.

 

[brain]

Part I of EPILEPSIA

Nice find Robin:

:clap: :clap: :clap:

Here's a more Updated Version:



Epilepsia - Neurotransmitter Measurements

Epilepsia

Volume 48 Issue s6, Abstracts from the 2007 Annual Meeting of the American Epilepsy Society Page 248-380, October 2007

To cite this article: (2007)
Poster Session III8:00 a.m.-2:00 p.m.
Epilepsia 48 (s6), 248–380.
doi:10.1111/j.1528-1167.2007.01252_5.x


Poster Session III
8:00 a.m.-2:00 p.m.

3.001
LEARNING IS A DANGEROUS THING: A COMPUTATIONAL APPROACH TO LEARNING, CONNECTIVITY AND EPILEPTOGENESIS
Abstract

David Hsu11Department of Neurology, University of Wisconsin – Madison, Madison, WI and M. Hsu11Department of Neurology, University of Wisconsin – Madison, Madison, WI (
1Department of Neurology, University of Wisconsin – Madison, Madison, WI
)

Rationale: Real brains learn by associative (Hebbian) processes, such that neurons that fire in the right sequence have the connection between them strengthened. Computational models of such systems, however, are highly unstable – they tend to develop either into overconnected systems that fire tonically, or they freeze into global silence. Thus real brains must have mechanisms for maintaining homeostasis of activity and connectivity. In particular, a specific level of connectivity can be defined such that information transmission and storage capacity are optimal. This level of connectivity is referred to as being critical. We describe a simple computational model that incorporates homeostasis of both activity and critical connectivity, and we show how these constraints lead to a natural interplay between the ability to learn, and the ability to develop seizures.

Methods: A stochastic neural system is defined with nodes that can either fire spontaneously or after receiving excitatory input from another node. A simple scaling mechanism scales the spontaneous firing probability S(i) for node i and the connection strengths P(i,j) linking node j to node i either up or down depending on the state of activity and the state of connectivity of each node. The conditions for stability are investigated both analytically and by exhaustive simulations using LTP, LTD and STDP rules of learning.

Results: (1) The spontaneous firing probability S contributes only 2–12% to the total activity; nonetheless, S must be greater than zero or else the system is unstable. (2) For systems that learn, firing rate homeostasis cannot guarantee homeostasis of connectivity. Homeostasis of connectivity is a separate principle. (3) Firing rate homeostasis is controlled by scaling of S. (4) Homeostasis of connectivity is controlled by scaling of P. (5) Scaling of P must be faster than scaling of S. (6) If S is perturbed away from its steady state value, then P will attempt to compensate. For instance, driving S to low levels causes P to rise to supercritical levels, and vice versa. (7) The post-ictal and acute post-deafferentation states result in levels of S that are below steady state values, and hence connectivity rises to supercritical levels lasting for many hours at a time.

Conclusions: Requiring a neural learning system to maintain stable levels of activity and connectivity introduces strong constraints on its dynamics. These constraints are of intrinsic interest. For instance, that real brains are spontaneously active derives from our first condition of stability. Secondly, we find that the post-ictal and acute post-deafferentation states should be supercritical. Since prolonged supercriticality helps burn into memory hypersynchronous states, such states are epileptogenic. This is an example of maladaptive learning. Thirdly, we predict that increasing the rate of spontaneous activity, for instance by deep brain stimulation, can decrease the time spent in the supercritical state and help prevent epileptogenesis.

3.002
IN VIVO CALCINEURIN INHIBITION INCREASES PICROTOXIN SEIZURE THRESHOLD AND DECREASES HIPPOCAMPAL EXTRACELLULAR GLYCINE CONCENTRATION
Abstract

Germán Sierra-Paredes11Biochemistry and Molecular Biology, Medical School, University of Santiago de Compostela, Santiago de Compostela, Spain, M. D. Vázquez-Illanes11Biochemistry and Molecular Biology, Medical School, University of Santiago de Compostela, Santiago de Compostela, Spain and G. Sierra-Marcuño11Biochemistry and Molecular Biology, Medical School, University of Santiago de Compostela, Santiago de Compostela, Spain (
1Biochemistry and Molecular Biology, Medical School, University of Santiago de Compostela, Santiago de Compostela, Spain
)

Rationale: Calcineurin (CAN) inhibitors have been reported to show anticonvulsant effect on experimental models of epilepsy. Seizures may be accompanied by modifications in brain CAN activity both in human studies and experimental models of epilepsy. In order to investigate if the anticonvulsant effect of CAN inhibition is mediated by changes in neurotransmitter extracellular concentrations, we have studied the effect of anticonvulsant doses of the CAN inhibitor ascomycin (ASC) on extracellular amino acid levels in the rat hippocampus.

Methods: Rat hippocampus was continuously perfused with an ASC solution (100 μM) through CMA/12 microdialysis probes at a flow rate of 2 μl/min during 4 hours with continuous EEG recording. After 2 hours, a picrotoxin solution (100–300 μM) was perfused during 5 min. Samples from the microdialysate were collected and analyzed by HPLC using pre-column derivatization with 6 aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) and fluorescence detection. In a second series of experiments, glutamate (100 μM) and glycine (100 μM) were perfused together with ASC to investigate the relationship among the anticonvulsant effect and extracellular amino acid levels.

Results: 100 μM ASC significantly increased picrotoxin seizure threshold in 70% of the animals studied. Mean threshold increase was 36,75%. ASC induced also a significant decrease on extracellular glycine levels (58.4 ± 6.1% of basal control levels, p < 0.01 by ANOVA, fig 1) with no effect on GABA (106.3 ± 8.6%), glutamate (94.9 ± 12.2%) and aspartate (89.8 ± 11.2% levels. 100 μM glutamate did not modify the effect of ASC on picrotoxin threshold, but 100 μM glycine prevented the anticonvulsant action of ASC.

Conclusions: The molecular mechanisms of the anticonvulsant effect of CAN inhibitors are unknown. We have shown that ASC microperfusion into the rat hippocampus increases picrotoxin seizure threshold and decreases extracellular glycine levels. The anticonvulsant effect of ASC is reversed by increasing glycine but not glutamate levels, indicating that the observed changes in glycine concentrations might be related to the anticonvulsant action of ASC.

Effect of ascomycin microperfusion on the hippocampal glycine levels. (n = 8; *p < 0.01)

3.003
CORTICAL SPREADING DEPRESSION AND SEIZURES CO-OCCUR AFTER ACUTE BRAIN INJURY
Abstract

Martin Fabricius11Dep. of Clinical Neurophysiology, Glostrup Hospital, Glostrup, Denmark;, S. Fuhr1,21Dep. of Clinical Neurophysiology, Glostrup Hospital, Glostrup, Denmark;2Dep. of Experimental Neurologie, Charite-Universitätsmedizin Berlin, Berlin, Germany, L. Willumsen33Dep. of Neurosurgery, Glostrup Hospital, Glostrup, Denmark, A. Strong44Department of Clinical Neurosciences, King's College London, London, United Kingdom, R. Bhatia44Department of Clinical Neurosciences, King's College London, London, United Kingdom, M. Boutelle55Department of Bioengineering, Imperial College London, London, United Kingdom, J. Dreier22Dep. of Experimental Neurologie, Charite-Universitätsmedizin Berlin, Berlin, Germany, J. Hartings66Division of Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Bethesda, MD, R. Bullock77Division of Neurosurgery, Medical College of Virginia, Richmond, VA and M. Lauritzen11Dep. of Clinical Neurophysiology, Glostrup Hospital, Glostrup, Denmark; (
1Dep. of Clinical Neurophysiology, Glostrup Hospital, Glostrup, Denmark;2Dep. of Experimental Neurologie, Charite-Universitätsmedizin Berlin, Berlin, Germany; 3Dep. of Neurosurgery, Glostrup Hospital, Glostrup, Denmark; 4Department of Clinical Neurosciences, King's College London, London, United Kingdom; 5Department of Bioengineering, Imperial College London, London, United Kingdom; 6Division of Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Bethesda, MD and 7Division of Neurosurgery, Medical College of Virginia, Richmond, VA
)

Rationale: Cortical spreading depression (CSD) is an acute pertubation of cerebral function related to migraine and acute brain injury in humans (Brain 2006;129:778–790). Animal studies demonstrate a complicated relation between CSD and seizure activity and suggest that CSD may cause secondary aggravation of brain injury. We tested the co-occurrence and interrelation of seizure activity and CSD in humans.

Methods: 54 patients underwent craniotomy after head injury or spontaneous haemorrhage. Electrocorticographic (ECoG) recordings were taken near foci of damaged cortical tissue for up to 10 days, starting at 5 hours to 12 days post ictus.

Results: One patient had seizure activity only, while 19 of the 54 patients only had CSDs. In 8 patients, CSD (5 to 34 episodes) and ECoGraphic seizures (1–81 episodes) co-occurred (p = 0.02). Clinically overt seizures were only ob-served in one patient. Phenytoin treatment decreased the susceptibility to both seizure activity and CSD in one patient. In three patients CSD was immediately preceded by seizure activity that was subsequently terminated by the same CSD. In one patient each CSD was followed by a pause in repetitive seizure activity, and in another patient we observed that CSD did not invade a locus with ongoing seizure activity. In two patients the two phenomena co-occurred without obvious interaction.

Conclusions: CSD and seizures interact in the acutely injured human brain in a complex fashion that reflect the various patterns observed in animal studies. CSD may increase the susceptibility of the cerebral cortex to seizures by suppressing synaptic inhibition, and seizure activity may trigger CSD. Conversely, CSD may terminate seizures. ECoG recordings may be a valuable tool in the assessment of cerebral cortical function and dysfunction in patients with acutely injured cerebral cortex. Non-invasive recording of CSD using surface EEG has not been possible so far, but our results indicate that if seizure activity is recorded in a patient with acute brain injury, it is likely that CSD epi-sodes occur too.

 

[brain]

Part II of Epilepsia

Part II of Epilepsia

3.005
LONG AND SHORT-TERM EFFECTS OF KAINATE-INDUCED STATUS EPILEPTICUS ON HIPPOCAMPAL NEUROGENESIS
Abstract

Toni M. Webster11Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury, NY, J. Avallone11Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury, NY, M. Kantrowitz11Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury, NY and L. K. Friedman11Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury, NY (
1Department of Neuroscience, New York College of Osteopathic Medicine, Old Westbury, NY
)

Rationale: Long-term (LT) effects of a single episode of kainate (KA) induced status epilepticus initiated in the perinatal period on hippocampal neurogenesis remain unknown. Therefore, we determined whether one early-life seizure induced on postnatal day 13 (P13) could have lasting effects into adulthood and whether these resemble short-term (ST) effects of a seizure later in life, P60.

Methods: We used single and double immunohistochemistry to study newly dividing cells throughout the hippocampus with antibodies bromo-deoxyuridine (BrdU) and Ki67, which label different stages of the cell cycle; neuronal and non-neuronal cell markers were used to identify cell types affected.

Results: In control rats, few scattered BrdU+ and Ki67+ dividing cells were detected lining the hilar border and other hippocampal layers. In contrast, ST rats expressed high numbers of BrdU+ and Ki67+ dividing cells within 48 hrs throughout hippocampal subfields. LT rats revealed a significant increase in the number of BrdU, but not Ki67, labeled nuclei within the CA3 and molecular cell layer (MCL) of the dentate gyrus (DG). Although there was no significant increase in progenitors within the granule cell layer (GCL), many BrdU+ cells were deeply incorporated, resembling the ST rats. Dispersion of the GCL was also noted in LT rats in various regions of dorsal and ventral blades. Percentages of proliferating cells co-labeling with neuronal and non-neuronal cell markers differed according to experimental group.

Conclusions: In ST rats, increased proliferation was observed with both antibodies; therefore, enhanced proliferation likely occurred around the time of the seizure, on P60. Accordingly, increases in LT rats were only detected with the BrdU marker, suggesting enhanced proliferation of newly dividing cells also occurred around the time of the seizure, on P13. Elevation of neuronal and non-neuronal progenitors following seizures in certain parts of the DG and altered distribution in the GCL of both groups suggests progenitors are not restricted to areas of neuronal vulnerability and incorporation of newly born granule cells occurs at the time of the insult. These may lead to permanently altered patterns of hippocampal circuitry regardless of when prolonged seizure episodes occur.

3.006
α2A ADRENERGIC RECEPTORS INHIBIT HIPPOCAMPAL EPILEPTIFORM ACTIVITY BY DECREASING SYNAPTIC TRANSMISSION AT RECURRENT CA3 SYNAPSES
Abstract

Chris W. Jurgens11University of North Dakota School of Medicine & Health Sciences, Grand Forks, ND and V. A. Doze11University of North Dakota School of Medicine & Health Sciences, Grand Forks, ND (
1University of North Dakota School of Medicine & Health Sciences, Grand Forks, ND
)

Rationale: The adrenergic system has been shown to exhibit robust antiepileptic properties without negative effects on learning and memory as often experienced with many antiepileptic therapies. This makes exploitation of adrenergic mechanisms a prime target for new antiepileptic treatments. Integral in learning and memory processes, hippocampal CA3 pyramidal cells are a common focus in temporal lobe epilepsy. We have previously identified an α2A AR mediated response on hippocampal CA3 pyramidal neurons which robustly inhibits CA3 epileptiform activity. We hypothesize that this receptor inhibits epileptiform activity by disrupting the recurrent excitatory drive between CA3 cells.

Methods: Pharmacological and surgical isolation techniques were used to examine the cell type responsible for this αAR response. Using whole-cell recordings in rat hippocampal slices, we examined excitatory post synaptic potential's (EPSC's), a measure of synaptic strength, evoked from the major connections of the CA3 pyramidal neurons to further localize this adrenergic effect.

Results: Pharmacological and surgical isolation localized this response to the CA3 pyramidal cells themselves. Preliminary evidence suggests that only recurrent CA3 synapses are inhibited by α2 stimulation, while the excitatory drive to and from the CA3 cells is not inhibited.

Conclusions: Overexcitation of CA3 recurrent synapses is thought to be a primary cause in temporal lobe seizures. Since this α2AR response is specific to CA3 recurrent synapses, this may explain how the adrenergic system may be antiepileptic while at the same time not affecting other areas of cognitive function such as learning or memory. (This study was funded by the Epilepsy Foundation (CWDJ), North Dakota EPSCoR through NSF grant EPS-0447679 (VAD), NSF CAREER award 0347259 (VAD), and NIH grant 5P20RR017699 from the COBRE program (VAD)).

3.007
GABA REGULATES CIRCUIT FORMATION OF NEWBORN CORTICAL NEURONS VIA NMDA CHANNEL ACTIVATION
Abstract

Doris D. Wang11Institute for Regeneration Medicine, University of California San Francisco, San Francisco, CA and A. R. Kriegstein11Institute for Regeneration Medicine, University of California San Francisco, San Francisco, CA (
1Institute for Regeneration Medicine, University of California San Francisco, San Francisco, CA
)

Rationale: The development of a balance between excitatory and inhibitory synapses is a critical step in the generation and maturation of functional circuits. Accumulating evidence suggests that neuronal activity is critical for achieving such a balance in the developing cortex. During corticogenesis, the principal inhibitory neurotransmitter GABA (υ-aminobutyric acid) exerts an excitatory effect on newborn neurons due to the high intracellular chloride gradient made by the Na+-K+-2Cl- cotransporter (NKCC1). GABAergic signalling precedes glutamatergic signalling in the developing neocortex as newborn neurons express GABAA receptors and receive GABAergic inputs before forming glutamaterigic synapses with each other. While GABA-induced excitation may influence the sequential development of inhibitory and excitatory synaptic inputs, the mechanism that mediates this process is unknown. In this study, we attempt to elucidate the role of GABA signaling on circuit formation of newborn neurons and the mechanism by which inhibition and excitation is established in the cortex.

Methods: To investigate the role of GABA in circuitry formation in the developing cortex, we used an RNA interference (RNAi) strategy to knockdown the expression of NKCC1, a Cl- importer responsible for GABA-induced depolarization in immature neurons. We performed in utero electroporation of plasmids co-expressing GFP and a previously characterized short hairpin RNA (shRNA) against Nkcc1 in 15-day-old embryonic mice. We used whole-cell recordings as well as confocal microscopy to study the physiological and anatomical evidence for synaptic integration of electroporated neurons during the first 3 week of postnatal life.

Results: We demonstrate here that GABA-induced depolarization plays several important roles during synaptogenesis and early cortical circuit formation. Immature neurons expressing Nkcc1-shRNA show both temporal delay and defects in synaptic integration. Furthermore, these cells demonstrate anatomical evidence of altered circuit development by displaying fewer branches, smaller soma size, and decreased dendritic spine density. In addition, we show that depolarizing GABAergic transmission is required for the formation of glutamatergic synapses via GABAergic activation of NMDA-receptors.

Conclusions: Here we show by knocking down NKCC1, that GABA-induced excitation regulates synapse formation and dendritic development of newborn cortical neurons in vivo. GABA-mediated depolarization also controls the formation of excitatory AMPA inputs via activation of NMDA channels. Our study identifies an essential role for GABA in the synaptic integration of newborn cortical neurons and suggests an activity-dependent mechanism for achieving the balance between excitation and inhibition in the developing cortex.

 

[brain]

Part III of Epilepsia

Part III of Epilepsia

3.008
HIPPOCAMPAL CA3 NMDA RECEPTORS PROTECT CA1 SUBFIELD FROM EXCITOTOXICITY
Abstract

Seiichiro Jinde11UGCB/NIMH, National Institutes of Health, Bethesda, MD, C. J. Cravens11UGCB/NIMH, National Institutes of Health, Bethesda, MD and K. Nakazawa11UGCB/NIMH, National Institutes of Health, Bethesda, MD (
1UGCB/NIMH, National Institutes of Health, Bethesda, MD
)

Rationale: It has been reported that NMDA receptor (NR) activation has neuroprotective role against kainic acid (KA)-induced excitotoxicity in adult murine hippocampus (Ogita et al., 2003). However, subfield-specific roles of hippocampal NRs in the neuroprotection against epileptic insult have not been investigated. Here we investigated the functional role of CA3 NRs in the KA-induced excitotoxicity using CA3 pyramidal cell-restricted NR subunit 1 knockout (CA3 NR1-KO or mutant) mice and its control littermates [i.e., C57BL/6N (B6), floxed-NR1 (fNR1) and CA3 pyramidal cell-cre (CA3-cre) mice; Nakazawa et al., 2002].

Methods: KA was administered i.p. to adult mice (12–20 wk of age) at 20 mg/kg body weight. Animals were monitored continuously for 2 h by video camera, and the onset and extent of behavioral seizure activity were recorded. Animals were killed at 3 h, 1 d, 7 d and 4 wk after KA treatment for the following histological studies. Neuronal damage was evaluated by Nissl staining, Fluoro Jade B and silver staining, and Mac-2 immunostaining. To detect the seizure-induced changes in GABAergic cells, brain sections were stained with the antibodies against GAD67 and palvalbumin (PV), respectively. c-fos immunoreactivity (IR) was monitored to evaluate neuronal excitability after the seizure.

Results: After KA injection, CA3 NR1-KO mice showed a higher severity of seizure and a higher occurrence of status epilepticus (continuous clonic seizures) than any other control genotypes. The c-fos induction 3 h after injection was higher in the mutant CA1 pyramidal cells and dentate granule cells than that of control mice. Surprisingly, mutant mice showed an extensive cell loss in the CA1 pyramidal cell layer, but not in CA3 cell layer at 7 d and 4 wk after injection. In contrast, seizure-induced neurodegeneration was rarely found in other control genotypes, which is consistent with empirical evidence that B6 strain is resistant to excitotoxic cell death. Further, we found differential changes in the expressions of GAD67-IR between mutant and control mice. One day after injection, the number of GAD67-positive cells was decreased at strata radiatum and oriens of field CA1 among all genotypes examined. However, mutants showed an increased GAD67-IR in the CA1 pyramidal layer suggesting enhanced feed-forward inhibition. Nevertheless, the mutant GAD67- and PV-IR were mostly absent from CA1 field 4 wk after injection, suggesting neurodegeneration of majority of CA1 GABAergic cells. In contrast, the expression of GAD67 and PV of CA1 field, once decreased 1 day after injection in the controls, was gradually returned to baseline from 7 d to 4 wk after injection.

Conclusions: The ablation of CA3 NR1 induced a higher susceptibility and an extensive cell loss in CA1 subfield after KA injection compared with the controls. The results suggest that CA3 NRs have a protective role of CA1 subfield, but not CA3 subfield against KA-induced excitotoxicity, which may be mediated by activation of feed-forward inhibition. This research was supported by the Intramural Research Program of the NIH.

CA3 NR1-KO mice showed an extensive cell loss in CA1.

3.009
ANTICONVULSANT ACTIVITY OF ANTIOXIDANTS
Abstract

Janet L. Stringer11Pharmacology, Baylor College of Medicine, Houston, TX and K. Xu11Pharmacology, Baylor College of Medicine, Houston, TX (
1Pharmacology, Baylor College of Medicine, Houston, TX
)

Rationale: Oxidative stress is a consequence of prolonged seizures and may contribute to seizure-induced brain damage and to the generation of epilepsy. However, a number of herbals products, which have antioxidant activity, have been shown to slow the onset of seizures or completely block the appearance of seizures suggesting that the generation of reactive oxygen species is involved in seizure initiation. This study tested the anticonvulsant activity of 8 antioxidants that have been shown to have activity in the central nervous system.

Methods: Trolox® (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), a water soluble analog of vitamin E (20 mg/kg), vitamin C (250 mg/kg), melatonin (20 mg/kg), curcumin (200 mg/kg), α-lipoic acid (25 mg/kg), deferoxamine (200 mg/kg), and HBED (N,N'-bis(2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid, 130 mg/kg) were each was tested for activity against acute seizures induced with pilocarpine (300 mg/kg ip preceded by 1 mg/kg methylscopolamine), kainic acid (10 mg/kg ip) or pentylenetetrazol (PTZ, 75 mg/kg sc). The antioxidants were administered intraperitoneally and all were dissolved in normal saline, except for melatonin (ethanol) and curcumin (DMSO). The time to onset of behavioral seizure activity for each convulsant was measured, as well as seizure score and mortality. For PTZ, the seizure duration was also measured. Parameters were averaged across animals in each treatment group and compared with a 1-way ANOVA with post-hoc Dunnett's comparison to control. Mortality was analyzed using a contingency table and Chi-square test.

Results: Trolox, vitamin C, and α-lipoic acid had significant anticonvulsant activity in the pilocarpine model, while HBED and deferoxamine increased mortality. The effects of melatonin were intermediate. The efficacy of Trolox was further examined with a dose-response curve, which showed maximal effects with 20 and 30 mg/kg. The results in the kainic acid model were not as distinct. There was a trend towards an anticonvulsant effect with Trolox, vitamin C and melatonin, but only curcumin significantly reduced the seizure score. Again, there was a trend towards an increase in mortality with HBED. None of the antioxidants had a significant effect against PTZ-induced seizures.

Conclusions: It was expected that the antioxidants would have the greatest effect on the latency to the first seizure. The results showed that a reduction in seizure score correlated with a trend towards an increase in latency. This would suggest that neuronal activity generates reactive oxygen species, which in turn contributes somewhat to synchronization or spread of the neuronal activity. However the anticonvulsant activity of the antioxidants is not uniform across the 3 experimental models. This group of antioxidants had no effect against PTZ, perhaps because of the rapid onset of the seizures in this model. None of the antioxidants were as consistently effective as a previously tested ginseng extract, which is reported to work as an antioxidant. The iron chelators, which have been shown to have neuroprotective activity, actually appear to increase mortality in these models.

3.010
GROUP I METABOTROPIC GLUTAMATE RECEPTOR ACTIVATION INDUCES ICTAL EPILEPTIFORM ACTIVITY AND LEADS TO A LONG-LASTING LOSS OF MEDIUM AND SLOW AFTERHYPERPOLARIZATIONS IN CA3 NEURONS
Abstract

Paul Rutecki1,21Neurology, Wm. Middleton VA Hospital, Madison, WI2Neurology, University of Wisconsin, Madison, WI, Y. Z. Pan22Neurology, University of Wisconsin, Madison, WI and L. Karr11Neurology, Wm. Middleton VA Hospital, Madison, WI (
1Neurology, Wm. Middleton VA Hospital, Madison, WI and 2Neurology, University of Wisconsin, Madison, WI
)

Rationale: Exposure to the group I metabotropic glutamate receptor (mGluR) agonist dihyrdroxyphenylglycine (DHPG) produces long-lasting changes in excitability and spontaneously occurring epileptiform activity in the CA3 region of rat hippocampal slices. The epileptiform activity consists of interictal discharges and long lasting (>2 s) synchronous activity that resembles ictal discharges. We evaluated the afterhyperpolarization (AHP) that follows neuronal firing in neurons exposed to DHPG and related the change to the pattern of epileptiform activity.

Methods: Rat hippocampal slices were prepared from 7–40 day old animals and exposed to 50 μM S- or 100 μM R,S-DHPG for 90–120 min. After exposure they were transferred to control artificial cerebrospinal fluid. Patterns of spontaneously occurring epileptiform activity were assessed. In the slices from older animals (30–40 days), sharp electrode recordings were made to characterize the AHP that followed repetitive firing produced by a depolarizing current pulse. The slices from younger animals (7–20) were used to perform whole-cell voltage-clamp recordings to assess the current responsible for the AHP.

Results: In slices that demonstrated ictal patterns, the AHP that followed depolarization and action potential generation was not prominent compared to control slices (peak amplitude in control 9.0 ± 1.1 vs. 1.3 ± 0.6 mV, p < 0.01). There was no difference in the resting membrane potential (−61.0 ± 1.4 for control and −59.1 ± 1.2 mV for DHPG-exposed). Control slices demonstrated a peak outward current of 173 ± 13 pA compared to DHPG-exposed neurons which had a peak current of 17 ± 5 pA (p < 0.01). This included a slow as well as a medium AHP current. Bath application of 1-EBIO (1 mM), a compound that enhances both the slow and medium AHP, led to a suppression of ictal discharges. Whole-cell voltage-clamp recordings demonstrated the return of the AHP current in DHPG-exposed neurons when 1-EBIO was bath-applied (12 ± 2 pA vs. 107 ± 11 pA, p < 0.01). DCEBIO (100 μM), a more selective compound for medium AHP also converted ictal slices to an interictal pattern.

Conclusions: The suppression of the AHP produced by DHPG exposure was associated with ictal patterns of epileptiform activity. Drugs that brought back the medium or slow AHP suppressed ictal discharges. These results support the hypothesis that the AHP can prevent the transition to ictal activity and loss of the AHP favors long lasting ictal activity.

Supported by VA research

3.011
INCREASED SYMPATHETIC NERVOUS SYSTEM CONTROL OF CARDIAC FUNCTION FOLLOWING STATUS EPILEPTICUS
Abstract

Cameron S. Metcalf11Pharmacology & Toxicology, University of Utah, Salt Lake City, UT and S. L. Bealer11Pharmacology & Toxicology, University of Utah, Salt Lake City, UT (
1Pharmacology & Toxicology, University of Utah, Salt Lake City, UT
)

Rationale: Status epilepticus (SE), a period of repeated or prolonged seizure activity, can lead to a number of cardiopulmonary complications including acute systemic and pulmonary hypertension, tachycardia, pulmonary edema, ventricular arrhythmias, generalized circulatory collapse, and cardiac failure. These complications contribute to an overall mortality of 21–22% in the period (up to several week) following SE. Furthermore, the aberrations in cardiac function are suggestive of autonomic dysregulation during and following SE. We propose SE produces an immediate increase in sympathetic nervous system (SymNS) activity that persists for several days and alters normal cardiac function and compensatory reflexes, contributing to morbidity and mortality following SE.

Methods: Seizures were induced in male Sprague-Dawley rats using pilocarpine (pilo; 30 mg/kg) following LiCl (127 mg/kg), which continued for 90 min before administration of diazepam (DZ; 10 mg/kg) to diminish seizure activity. Seizures were monitored by direct observation and electroencephalogram (EEG) recordings made from unilateral electrodes placed dorsal to the temporal lobe. Animals recovered for one week before polyethylene catheters were placed in the femoral artery and vein. Arterial pulse pressure recordings were obtained and autonomic input to the heart (SymNS vs. parasympathetic nervous system, PsymNS) was evaluated by estimating heart rate variability (HRV) in both time (interbeat interval, R-R interval, RR) and frequency (low frequency, LF and high frequency, HF) domains. In addition, cardiac contractility was assessed by measuring the mean rate of pressure increase (dP/dt) during contraction.

Results: All animals that received pilocarpine had repeated seizure activity, until administration of DZ. The root mean square of the standard deviation of RR intervals (RMSSD, a measure of HRV), was decreased, while both LF and the ratio LF/HF were significantly greater in pilo treated animals compared to control animals. All of these alterations in HRV are indicative of increased cardiac SymNS tone. Additionally, dP/dt was significantly greater in pilo animals.

 

[brain]

Part IV of Epilepsia

Part IV of Epilepsia

3.012
MORPHOLOGICAL CHANGES OF THE JUVENILE HIPPOCAMPUS ARE SIMILAR AFTER SINGLE VERSES MULTIPLE EARLY-LIFE SEIZURES
Abstract

Grace LaTorre11Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY, S. Majumudar11Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY, G. Torres11Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY, J. Chabla11Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY and L. K. Friedman11Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY (
1Neuroscience, New York Collge of Osteopathic Medicine, Old Westbury, NY
)

Rationale: We recently have shown that multiple early-life seizures attenuate glutamate stimulated calcium permeability which may increase adaptive responses later in life that lead to neuroprotection. An important function of dendritic spines may be to protect neurons from highly elevated concentrations of calcium that follow sustained early-life seizures.

Methods: Our previously established model was used to determine whether typical changes in morphology of CA1 pyramidal and granule cell neurons induced by a single episode of status epilepticus in prepubescent animals are attenuated by early-life seizures. The Golgi method was used for morphological analysis of the hippocampus of postnatal (P) day 20 rats 72 hrs after a single kainate (KA) seizure (1x KA) or following three seizures (3x KA), induced on P6, P9 and P20.

Results: After 1x KA in the CA1, a large decrease in the number of apical, but not basal branches, was observed. Long thin and short stubby dendritic spine density was significantly reduced. Spine loss was accompanied by swellings and shortening of dendritic segments. In the dentate gyrus, a five fold increase in basal dendrites of granule neurons was measured relative to naive P20 controls. After 3x KA, relatively similar decreases or increases were observed among respective pyramidal and granule cell populations.

Conclusions: The lack of further CA1 dendritic pruning after 3x KA may be due to adaptive responses whereby significant loss in excitatory morphology may be complete after the initial insult. Similarly, non-progressive changes in granule cell basal dendrite number or outgrowth present evidence for their role in adaptation following early-life seizures possibly by reducing calcium permeability.

3.013
SYNERGISM OF LACOSAMIDE AND FIRST-GENERATION AND NOVEL ANTIEPILEPTIC DRUGS IN THE 6 HZ SEIZURE MODEL IN MICE
Abstract

Thomas Stoehr11Schwarz Biosciences, Monheim, Germany, P. Shandra33Odessa National University, Odessa, Ukraine, O. Kashenko22Odessa State Medical University, Odessa, Ukraine and A. Shandra22Odessa State Medical University, Odessa, Ukraine (
1Schwarz Biosciences, Monheim, Germany; 2Odessa State Medical University, Odessa, Ukraine and 3Odessa National University, Odessa, Ukraine
)

Rationale: Lacosamide (LCM) is a functionalized amino acid that shows a more potent and effective anticonvulsant profile in animal models when compared to conventional antiepileptics. New antiepileptic drugs (AEDs) are initially licensed as add-on treatment, often with no evidence to suggest which existing therapies they should be employed with. In addition, approximately 30% of patients with epilepsy are prescribed polytherapy regimes. There is, thus, a clear need to develop a rational basis for AED polytherapy. The objective of this study was the isobolographic evaluation of the interaction between LCM and a number of other AEDs.

Methods: The anticonvulsant effect of LCM with other AEDs (carbamazepine (CBZ), phenytoin (PHT), valproate (VPA), lamotrigine (LTG), topiramate (TPM), gabapentin (GBP) and levetiracetam (LEV)) at fixed ratios of 1:3, 1:1 and 3:1 was evaluated in the 6 Hz-induced seizure model in mice. The protective action of an AED was defined as the absence of seizure. Furthermore, motor side effects of AED combinations was assessed in the rotarod test.

Results: All studied AEDs produced dose-dependent anticonvulsant effects against 6 Hz induced seizures. Combinations of LCM with CBZ, LTG, TPM, GBP or LEV were supraadditive (synergistic). All other LCM/AED combinations displayed additive effects with a tendency towards supraadditivity. Furthermore, no enhanced adverse effects were induced by combinations of LCM with these AEDs as assessed in the rotarod test.

Conclusions: The isobolographic analysis revealed that combinations of LCM with novel AEDs (TPM, GBP, LTG or LEV) or with CBZ are associated with supraadditive anticonvulsant effects. Similar but less profound supraadditive effects were seen with LCM in combination with PHT or VPA. In contrast, infra-additive effects were seen on motor side effects for combinations in comparison to equipotent doses of AEDs alone. (Research funding provided by Schwarz Biosciences).

3.014
ANALYSIS OF RESTING-STATE FMRI REVEALS ABNORMAL HIPPOCAMPUS-PRECUNEUS CONNECTIVITY IN PATIENTS WITH TEMPORAL LOBE EPILEPSY

Roman Rodionov1,21Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom2National Society for Epilepsy, London, United Kingdom, H. Laufs1,31Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom3Brain Imaging Center and Klinik für Neurologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany, R. Thornton1,21Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom2National Society for Epilepsy, London, United Kingdom, M. Chupin1,21Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom2National Society for Epilepsy, London, United Kingdom, J. S. Duncan1,21Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom2National Society for Epilepsy, London, United Kingdom and L. Lemieux1,21Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom2National Society for Epilepsy, London, United Kingdom (
1Department of Clinical and Experimental Epilepsy, Institute of Neurology, University Colledge London, London, United Kingdom; 2National Society for Epilepsy, London, United Kingdom and 3Brain Imaging Center and Klinik für Neurologie, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
)

Rationale: Refractory temporal lobe epilepsy (TLE) can be treated by resection of the affected temporal lobe including the hippocampus. Functional MRI can be used as a diagnostic tool to assess hippocampal functional connections non-invasively. In a previous resting-state EEG-fMRI study [1] it was shown that spike-correlated increases in BOLD activity in the hippocampus of the affected temporal lobe are typically associated with decreased BOLD signal in the precuneus. Here using fMRI data only we investigated whether the functional connectivity (FC) between the hippocampus and the precuneus was different in patients with TLE compared to healthy volunteers and thus may serve to identify abnormal temporal lobe activity.

Methods: Eighteen TLE patients and nine healthy controls were studied. Resting-state T2*-sensitive echo planar images were acquired at 3T (GE Signa Excite HDX) and 1.5 T (GE Signa Horizon Echospeed). Using SPM5, images were realigned and normalized (http://www.fil.ion.ucl.ac.uk/). The following ROI's were defined for each subject: (1) individually segmented hippocampi using high resolution T1 images [2], (2) precuneus defined as a ROI according to the WFU PickAtlas (http://www.ansir.wfubmc.edu). Following regression of head motion and cardiac-related effects, and of signal changes from the CSF and white matter, BOLD signal time courses were extracted by averaging across each ROI using MarsBar (http://marsbar.sourceforge.net). Correlation coefficients were calculated as a measure of FC. Non-parametric statistical tests (Wilcoxon rank sum criterion and t-test) were performed to test whether hippocampal-precuneal (Hc-PC) FC differ (i.e. towards anti-correlation) in patients than in controls (one sided t-test).

Results: FC was significantly (p < 0.01) different for patients compared to controls (see Table). Specifically, correlation coefficients in patients were significantly lower than those in the control group reflecting a tendency towards anti-correlation in the former. There was no significant difference in Hc-PC FC between patients scanned at 1.5T vs 3T (p > 0.2).

Conclusions: We demonstrated that resting state fMRI Hc-PC functional connectivity in a group of TLE patients was significantly different from that in healthy subjects. This result can be seen as generalisation of previous findings based on EEG-correlated fMRI and motivates further studies testing whether the proposed approach can provide a reliable marker of TLE and possibly focus lateralisation. (This work is supported by Medical Research Council grant #G0301067)
References:


1. Laufs H., et al., Hum Brain Map, 2006 Nov 28; [Epub ahead of print]

2. Chupin M., et al., Neuroimage, 2007, 34(3):996–1019.

Significance of difference in LHc-PC and RHc-PC functional connectivity

3.015
HOW DOES PILOCARPINE AFFECT BLOOD-BRAIN BARRIER FUNCTION?
Abstract

Chiara Caponi11Lerner Research Institute, Cleveland, OH, F. Bertolini11Lerner Research Institute, Cleveland, OH, N. Marchi11Lerner Research Institute, Cleveland, OH, A. Batra11Lerner Research Institute, Cleveland, OH and D. Janigro11Lerner Research Institute, Cleveland, OH (
1Lerner Research Institute, Cleveland, OH
)

Rationale: The most widely used model of temporal lobe epilepsy consists of peripheral administration of the cholinergic muscarinic agonist pilocarpine which leads to status epilepticus and subsequent spontaneous seizures. It has been generally accepted that these effects are primarily due to cholinergic activation of limbic cortex and hippocampus. However, recent evidence pointed to an alternative mechanism of action that involved peripheral inflammation and leakage across the blood-brain barrier (1, 2).The exact mechanisms of this unexpected cerebrovascular effect of pilocarpine are not yet understood. This prompted us to further investigate the actions of pilocarpine on white blood cells and brain endothelium.

Methods: The effect of pilocarpine on BBB permeability was evaluated in vitro using a Transwell system obtained with a co-culture of human derived brain endothelial cells and human astrocytes in the presence or not of monocytes. Cytokine (IL-6, TNF-alpha and IL-1beta) release from monocytes co-cultured with endothelial cells following exposure to pilocarpine was measured by ELISA test. Morphological changes of endothelial cells were evaluated by fluorescent immunocytochemistry using beta-actin staining. MMP activity was evaluated by zymography. NO production by monocyte was quantified through amperometric detection. Real time NO measurements were taken with nano-molar sensitivity in a flow-based system obtained by a co-culture of human derived brain endothelial cells with circulating mononuclear blood cells.

Results: Pilocarpine increased BBB permeability to serum protein in vivo, and decreased trans-endothelial electrical resistance in vitro. Following exposure to pilocarpine (1.4 mM), we measured a rapid (minutes) release of nitric oxide, paralleled by increased levels of IL-6, but not TNF-alpha or IL-1beta. This was primarily due to activation of receptors on white blood cells occurring in spite of pretreatment with scopolamine (4 μM) and it was associated with MMP2 and MMP9 increased activity. The downstream effects of nitric oxide and cytokine/MMP release by white blood cells consisted of polymerization of endothelial cell beta-actin with subsequent loss of junctional integrity.

Conclusions: Our results suggest that proinflammatory changes induced by peripherally administered pilocarpine consist of a cascade of events that include white blood cell activation and BBB damage induced by cytokine- and NO-mediated actions on endothelial cells.

(Supported by NIH-NS43284, NIH-HL51614, NIH-NS46513, NIH-NS049514 and NIH-NS38195)
1)

Marchi, N. et al. In vivo and in vitro effects of pilocarpine: relevance to epileptogenesis. Epilepsia in press, (2007).
2)

Janigro D. et al. Adenosine-induced release of nitric oxide from cortical astrocytes. Neuroreport (1996 Jul 8)

 

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Part V of Epilepsia

Part V of Epilepsia

3.016
PERSISTENT DOWNREGULATION OF HIPPOCAMPAL PYRAMIDAL HCN CHANNELS FOLLOWING PILOCARPINE-INDUCED STATUS EPILEPTICUS
Abstract

Sangwook Jung11Neurology, University of Washington at Seattle, Seattle, WA, T. D. Jones11Neurology, University of Washington at Seattle, Seattle, WA, J. N. Lugo Jr.22Pediatrics-Neurology, Baylor College of Medicine, Houston, TX, A. H. Sheerin33Neurological Surgery, University of Washington at Seattle, Seattle, WA, J. W. Miller11Neurology, University of Washington at Seattle, Seattle, WA, R. D'Ambrosio33Neurological Surgery, University of Washington at Seattle, Seattle, WA, A. E. Anderson22Pediatrics-Neurology, Baylor College of Medicine, Houston, TX and N. P. Poolos11Neurology, University of Washington at Seattle, Seattle, WA (
1Neurology, University of Washington at Seattle, Seattle, WA; 2Pediatrics-Neurology, Baylor College of Medicine, Houston, TX and 3Neurological Surgery, University of Washington at Seattle, Seattle, WA
)

Rationale: It has been shown that changes in ion channel function occur in animal models of epilepsy at both acute and chronic time points following status epilepticus. However, it remains unclear how ion channel dysfunction is linked to the development of the epileptic state. We thus investigated how alterations in the biophysical properties of hyperpolarization-activated cation (HCN) channels, an ion channel implicated in experimental epilepsy, correlate with the development of epilepsy.

Methods: We performed video-EEG monitoring on pilocarpine-treated rats during acute (one week) and chronic (two to four week) periods following pilocarpine-induced status epilepticus (SE) to determine onset of spontaneous seizures. Cell-attached and whole-cell patch-clamp recordings in CA1 hippocampal pyramidal neuron dendrites were performed in the acute and chronic periods to measure changes in the properties of Ih, the current produced by HCN channels, and Western blot analysis was used to measure HCN protein expression.

Results: Video-EEG monitoring of pilocarpine-treated rats showed that seizures were observed beginning as early as day 3 post-pilocarpine. Racine class 0–2 seizures were frequent at 1–2 week post-pilocarpine, then declined in frequency, while class 3–5 seizures had increased in frequency by 3–4 week post-pilocarpine. By the end of 4 week post-pilocarpine, 85% of rats had experienced spontaneous recurrent seizures. In the acute and chronic periods post-pilocarpine, dendritic Ih densities from pilocarpine-treated animals were significantly reduced compared to age-matched, sham-injected animals. Further, the Ih half-maximal activation voltage (V1/2) from pilocarpine-treated animals was significantly hyperpolarized during the acute period, and increasingly so during the chronic period compared to sham-injected animals. Dendritic current-clamp recordings during the chronic period showed that input resistance and action potential firing from pilocarpine-treated animals were also significantly increased compared to naive animals. Further, Western blot analysis showed that there was a significant loss of hippocampal HCN1 and HCN2 protein expression in the acute period, and persistent loss of HCN1 in the chronic period. Interestingly, rats given phenobarbital during the first week post-pilocarpine to suppress spontaneous seizures showed a similar downregulation of HCN channels (decreased Ih and HCN1/2 protein expression) as rats treated with pilocarpine alone.

Conclusions: Our results show that downregulation of HCN channel function and expression in the dendrites of CA1 hippocampal pyramidal neurons occurs in the acute period following pilocarpine-induced SE and persists during the emergence of chronic, spontaneous seizures. This early and progressive HCN downregulation results in increased neuronal excitability. We have also shown that spontaneous seizure activity in the acute period does not itself cause HCN channel downregulation, suggesting that the downregulation of HCN channels results from, and may contribute to, the process of epileptogenesis.

3.017
LEPTIN INHIBITS NEURONAL BURSTING IN CULTURED HIPPOCAMPAL NEURONS
Abstract

Hai Xia Zhang11Department of Neurology, Washington University, St. Louis, MO and K. L. Thio1,21Department of Neurology, Washington University, St. Louis, MO2Pediatric Epilepsy Center, Washington University, St. Louis, MO (
1Department of Neurology, Washington University, St. Louis, MO and 2Pediatric Epilepsy Center, Washington University, St. Louis, MO
)

Rationale: Leptin inhibits the Ca2+ oscillations and epileptiform-like activity observed in hippocampal neurons when exposed to a Mg2+-free extracellular solution. To further test leptin's potential as an anticonvulsant, we examined the effects of leptin on neuronal bursting induced by a Mg2+-free extracellular solution. We also examined the effects of leptin on action potentials, input resistance, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) currents, and N-methyl-D-aspartate (NMDA) currents.

Methods: Current and voltage clamp recordings were obtained from cultured embryonic mouse hippocampal neurons using the whole-cell patch clamp technique. The effects of leptin on action potentials, input resistance, and AMPA currents were examined with 1 mM extracellular Mg2+, but the effect on NMDA currents was examined in a Mg2+-free extracellular solution containing 10 μM glycine. Neurons were subjected to 700 ms current steps ranging from −40 pA to +40 pA in 10 pA increments to generate action potentials and to determine input resistance. AMPA and NMDA were applied using a flow-tube system.

Results: Cultured hippocampal neurons generally fired isolated action potentials with 1 mM Mg2+ in the extracellular solution. When exposed to a Mg2+-free extracellular solution, neurons produced bursts of action potentials superimposed on 0.5–2 s depolarizing envelopes resembling paroxysmal depolarizing shifts. One nM leptin decreased the overall action potential frequency from 1.8 ± 0.3 Hz to 1.0 ± 0.2 Hz (p < 0.05), and 10 nM leptin decreased the overall action potential frequency from 0.9 ± 0.2 Hz to 0.6 ± 0.1 Hz (p < 0.05). However, 0.1 nM leptin did not significantly change the overall action potential frequency. In 1 mM extracellular Mg2+, 700 ms current steps of +20 pA, +30 pA, and +40 pA evoked 9 ± 1, 11 ± 1, and 13 ± 1 action potentials, respectively. Leptin (0.1, 1, and 10 nM) did not change the number of action potentials evoked by these steps. Leptin also did not alter action potential amplitude (107 ± 2 mV), duration at half-maximal amplitude (2.3 ± 0.2 ms), or threshold (−39 ± 2 mV). Leptin (0.1, 1, and 10 nM) did not change the resting membrane potential (−61 ± 2 mV) or input resistance (1030 ± 98 MΩ). Finally, leptin (0.1, 1 and 10 nM) did not alter the amplitude of the peak current evoked by 100 μM AMPA or 100 μM NMDA.

Conclusions: These results indicate that leptin inhibits neuronal bursting in cultured hippocampal neurons induced by a Mg2+-free extracellular solution. They also suggest that this anticonvulsant effect does not result from a change in action potentials, resting membrane properties, or modulation of postsynaptic glutamate receptors.

(Sources of funding – NIH, Epilepsy Foundation, Alafi Fund)

 

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Part VI of Epilepsia - One more interesting Abstract

Part VI of Epilepsia

3.069
BLOOD GENOMIC PROFILING OF HUMAN TEMPORAL LOBE EPILEPSY
Abstract

Evan J. Fertig1,21Department of Neurology, Yale University School of Medicine, New Haven, CT2Department of Neurosurgery, Yale University School of Medicine, New Haven, CT, S. Azam11Department of Neurology, Yale University School of Medicine, New Haven, CT, R. S. Mann2,32Department of Neurosurgery, Yale University School of Medicine, New Haven, CT3W. M. Keck Foundation Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT, S. Mane33W. M. Keck Foundation Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT, D. D. Spencer22Department of Neurosurgery, Yale University School of Medicine, New Haven, CT and N. C. de Lanerolle22Department of Neurosurgery, Yale University School of Medicine, New Haven, CT (
1Department of Neurology, Yale University School of Medicine, New Haven, CT; 2Department of Neurosurgery, Yale University School of Medicine, New Haven, CT and 3W. M. Keck Foundation Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, CT
)

Rationale: Blood gene expression profiles can differentiate neurological diseases including epilepsy (Tang et al., Arch. Neurol. 62: 210–215, 2005). A previous retrospective analysis of hippocampal pathology in human temporal lobe epilepsy (TLE) revealed patient subcategories associated with different surgical outcomes: mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE) and mass associated TLE (MaTLE) had good surgical outcome, whereas paradoxical TLE (PTLE) had a poor outcome. The objective of this study was to determine if TLE patients could be distinguished from other types of epilepsy, and if MTLE could be distinguished from PTLE on the basis of blood gene expression profiles.

Methods: Clinical data was collected, and subjects were categorized using the International League Against Epilepsy classification. Subjects who underwent temporal resections were further characterized as MTLE or PTLE. Whole blood was collected in Tempus RNA tubes, and RNA was isolated using the Tempus protocol. Gene expression profiles were determined by microarray analysis using the Affymetrix human GeneChip U133 Plus 2.0 array. Unsupervised hierarchical cluster analysis and multidimensional scaling was performed to look for class identification. ANOVA analysis was used to determine differentially expressed genes.

Results: Twenty-seven epileptic subjects and 8 controls were enrolled. Eleven of the subjects had temporal resections; pathology was MTLE in 9 and PTLE in 2. Eleven subjects had cryptogenic localization-related epilepsy (CLRE) and 5 subjects had idiopathic generalized epilepsy (IGE). The average age of controls was 24.9 yr and subjects with epilepsy – IGE, CLRE, MTLE, and PTLE were 24, 31.1, 43 and 30.5 yr respectively. AED types overlapped between patient groups. Of the subjects on AEDs, 2 were on valproate (VPA) monotherapy, 3 on lamotrigine (LTG) monotherapy, 2 on carbamazepine (CBZ) monotherapy, and 1 on oxcarbazepine (OXC) monotherapy. Postoperative seizure freedom was achieved in 56% of MTLE and 0% of PTLE subjects. Controls clustered separately from all epileptic subjects. Epileptic types did not show independent clustering, but both PTLE subjects were in the same cluster. TLE subjects did not cluster by outcome. Subjects on VPA monotherapy clustered independently of subjects on CBZ monotherapy, LTG monotherapy, or OXC monotherapy.

Conclusions: TLE does not have a distinct gene expression profile, but epileptic subjects have a unique profile compared to controls. This difference is not related to seizure freedom or AED therapy. Whereas MTLE subjects are found in several clusters, the PTLE share the same cluster. In agreement with Tang et al. (Acta Neurol. Scand. 109: 159–168, 2004), VPA monotherapy has a unique blood gene expression pattern compared to CBZ monotherapy, and in the present study also LTG and OXC monotherapy. Genes that are differentially expressed between epileptic subjects and controls, and VPA and other monotherapies will be discussed.