Serotonergic inhibition of limbic and thalamic seizures in cats

To clarify the role of the serotonergic system in limbic and thalamic epileptic activity, we examined the effects of 5-hydroxytryptophan (5-HTP, 20 and 40 mg/kg) on fully kindled seizures from the hippocampus and lateral geniculate nucleus. The intraperitoneal administration of 20 mg/kg 5-HTP exerted no anticonvulsant effect on hippocampal kindled seizures, and a higher dose (40 mg/kg) produced a significant reduction in the behavioral seizure stage. 5-HTP at 20 mg/kg displayed no suppressive effect on lateral geniculate seizures, and 5-HTP at 40 mg/kg significantly reduced both the seizure stage and afterdischarge duration. Our data suggest that serotonergic mechanisms play an inhibitory role in seizures kindled from these brain regions.