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Effects of GABAB receptor antagonists on two models of focal epileptogenesis
S Brailowsky1, T Montiel, S Meneses
1Departamento de Neurociencias, Universidad Nacional Autónoma de México. sbrailow@ifcsun 1.ifisiol.unam.mx
Abstract:
The acute effects of two GABAB receptor antagonists (phaclofen and CGP-35348) were studied in two types of epileptogenic activity: that produced by intracortical injections of baclofen and that appearing after withdrawal of chronic intracerebral GABA infusion (the GABA-withdrawal syndrome, GWS). Intracortical baclofen induced two types of electrographic paroxysmal discharges: one consisting of single spike-and-wave (pattern I) and another of polyspike-and-wave patterns (pattern II). Both patterns showed similar latencies and temporal evolution of spike frequency discharges. Phaclofen, applied directly into the baclofen-induced epileptogenic focus, suppressed pattern II but was ineffective in modifying both pattern I and the GWS. CGP-35348, administered systemically, inhibited both patterns I and II. Intracortical microinjection of baclofen or phaclofen in rats showing a GWS had no effect, nor the systematically given CGP 35348. These results indicate a differential participation of GABAB receptors in GABA-related epileptic syndromes of cortical origin.
Insights
This study investigated GABAB receptor antagonists in epilepsy models. Systemic CGP-35348 inhibited both baclofen-induced epileptic patterns, while local phaclofen only suppressed one, suggesting differential GABAB receptor roles in cortical epilepsy.
Area of Science:
- Neuroscience
- Pharmacology
- Epilepsy Research
Background:
- GABAB receptors play a crucial role in regulating neuronal excitability.
- Understanding their involvement in different epileptic syndromes is essential for developing targeted therapies.
- GABA withdrawal syndrome (GWS) is a model of cortical epilepsy.
Purpose of the Study:
- To investigate the acute effects of GABAB receptor antagonists phaclofen and CGP-35348 on two distinct types of cortical epileptogenic activity.
- To differentiate the roles of GABAB receptors in baclofen-induced seizures and GABA withdrawal syndrome (GWS).
Main Methods:
- Studied acute effects of phaclofen and CGP-35348 on epileptogenic activity induced by intracortical baclofen.
- Investigated antagonist effects on GABA withdrawal syndrome (GWS) following chronic intracerebral GABA infusion.
- Administered antagonists via intracortical microinjection and systemic administration in rat models.
Main Results:
- Intracortical baclofen induced two patterns of electrographic discharges: pattern I (single spike-and-wave) and pattern II (polyspike-and-wave).
- Local phaclofen suppressed pattern II but not pattern I or GWS.
- Systemic CGP-35348 inhibited both pattern I and pattern II, but not GWS.
- Neither intracortical nor systemic administration of antagonists affected GWS.
Conclusions:
- GABAB receptors exhibit differential involvement in distinct cortical epileptic syndromes.
- Systemic GABAB receptor blockade is effective against certain seizure types, but not GABA withdrawal syndrome.
- These findings highlight the complexity of GABAB receptor function in epilepsy and suggest specific therapeutic targets.