The effects of intracerebroventricular AM-251, a CB1-receptor antagonist, and ACEA, a CB1-receptor agonist, on penicillin-induced epileptiform activity in rats

P>Purpose: Several results support the conclusion that the cannabinoid system has a role in generation and cessation of epileptic seizures. The aim of this study was to evaluate the effects of intracerebroventricular AM-251 [N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide], a CB1-receptor antagonist, and ACEA (arachidonyl-2-chloroethylamide), a CB1-receptor agonist, on penicillin-induced epileptiform activity in rats. Methods: In the first set of experiments, 30 min after penicillin injection, AM-251, at doses of 0.125, 0.25, 0.5, and 1 mu g, was administered intracerebroventricularly (i.c.v.). In the second set of experiments, 30 min after penicillin injection, ACEA, at doses of 2.5, 5, 7.5, and 15 mu g (i.c.v.), was administered. In the third set of experiments, AM-251, at doses of 0.125 and 0.25 mu g (i.c.v.), was administered 10 min before ACEA (7.5 mu g, i.c.v.) injection. Results: ACEA, at a dose of 7.5 mu g, significantly decreased the frequency of penicillin-induced epileptiform activity without changing the amplitude. ACEA, at doses of 2.5, 5, and 15 mu g, had no impact on either frequency or amplitude of epileptiform activity. AM-251, at doses of 0.25 and 0.50 mu g, significantly increased the frequency of epileptiform activity. AM-251, at a dose of 0.25 mu g (i.c.v.), was the most effective in changing the frequency of penicillin-induced epileptiform activity, and it also caused status epilepticus-like activity. AM-251, at doses of 0.125 and 0.25 mu g, 10 min before ACEA (7.5 mu g), reversed the anticonvulsant action of ACEA. Discussion: The results of the present study provide electrophysiologic evidence for the role of CB1 receptors in regulating the frequency of epileptiform activity in the model of penicillin-induced epilepsy. To elucidate the precise mechanism of cannabinoid action in the brain during seizure, more advanced electrophysiologic and neurochemical studies are required.