Dopaminergic regulation of epileptic activity.

We evaluated the role of dopamine systems in the propagation of epileptic Focal, limbic seizures were produced by systemically administered pilocarpine (200 mg/kg, i.p.); as previously described this dose produces limbic stereotypes but neither convulsions nor seizure-related brain damage. The systemic pretreatment with D-1, but not D-2, agonists induced convulsions identical to those produced by a higher, convulsant dose of pilocarpine (400 mg/kg). Conversely, the pretreatment with D-1 receptor antagonists prevented the convulsions whereas the D-2 antagonists facilitated the pilocarpine-induced seizures. Furthermore, we studied the effects of intracerebral injections of dopamine agents on seizures induced by pilocarpine. Nigral microinjection of D-1 agonists strongly induced motor seizures in rats treated with the low dose of pilocarpine. On the other hand, microinjection of D-1 antagonists prevented the motor seizures induced by the high dose of pilocarpine. This study indicates that the two dopamine receptor subtypes, D-1 and D-2, exert opposing roles in the control of epilepsy propagation. Substantia nigra pars reticulata appears to be primarily involved in the dopamine-mediated modulation of seizures.