Dopamine agonists and cobalt-induced epilepsy in the rat.

1 Electrocorticogram (ECoG) recordings were made from conscious rats which had cortical implants of cobalt. The epileptiform spike activity was then assessed by means of an automated technique, based on peak angle measurements. 2 Apomorphine (0.5, 1.0 and 2.0 mg/kg i.p.) and lisuride (0.1, 0.25, 0.5 and 1.0 mg/kg i.p.) inhibited spike activity in established primary and secondary foci in a dose-dependent manner. Bromocryptine (10 and 20 mg/kg i.p.) and CF 25-397 (40 mg/kg i.p.) had a similar effect but only after a latent period of several hours. Chronic administration of bromocryptine (20 mg/kg i.p. daily) attenuated the normal development of the foci following implantation. 3 Pimozide (1 mg/kg i.p.) potentiated cortical epileptic activity in cobalt-implanted rats and blocked the antiepileptic effects induced by the dopamine agonists. 4 Intrastriatal administration of dopamine (25 micrograms) or apomorphine (60 micrograms) suppressed epileptiform spikes in the cortex. Destruction of striatal catecholamine terminals by 6-hydroxydopamine increased the spike activity. 5 It is concluded that the striatum may play an essential part in mediating the anti-epileptic effects of dopamine and its agonists in this model of epilepsy.