Modulation of postdecapitation convulsions in rats by alpha-adrenergic and 5-hydroxytryptamine1A agents

Postdecapitation convulsions were analyzed in rats after the administration of a variety of adrenergic and serotonergic agents. Drugs were selected on the basis of their relative affinities for 5-hydroxytryptamine1A, alpha 2-adrenergic and/or alpha 1-adrenergic receptors. The 5-hydroxytryptamine1A-selective agonists, 8-hydroxy-N,N-dipropyl-2-aminotetralin and buspirone, significantly increased the duration of the convulsions. The alpha 2-adrenergic antagonists, yohimbine and corynanthine, had no affect on either the latency or duration of the convulsions. By contrast, each of the three alpha 1-adrenergic agents increased the latency and decreased their duration. However, the order of potency was WB 4101 greater than ipsapirone greater than prazosin and this rank order did not correlate with drug potencies for the alpha 1-adrenergic receptor as determined by radioligand binding studies. The high potency of both ipsapirone and WB 4101 in inhibiting the postdecapitation convulsions may relate to the combined effects of the drugs at both alpha 1-adrenergic and 5-hydroxytryptamine1A receptors.