Central cardiovascular actions of d-tubocurarine and inhibition of the hypotensive effect of clonidine.

Intracisternal (i. cist.) administration of d-tubocurarine (0.025-0. 100 mg. kg-1) in alpha-chloralose-anaesthetized dogs caused a dose-related increase in blood pressure associated with seizures. When injected in dogs pretreated with guanethidine (15 mg. i.v.), d-tubocurarine elicited the same effect while bilateral adrenalectomy abolished the pressor response. The hypotensive effect of clonidine (0.003 mg. kg-1 i. cist.) was reversed when clonidine was given after the alkaloid. These results suggest possbile interactions of the drugs at central GABA-ergic, glycinergic or cholinergic synapses.