Adrenoceptor action of neurons of the superior cervical and caudal mesenteric sympathetic ganglia in cats

Abstract

Experiments on the superior cervical and caudal mesenteric sympathetic ganglia of cats showed that dopamine (DA), like noradrenalin (NA) and adrenalin (A), inhibits cholinergic conduction. DA activity in the superior cervical ganglion is 2 and 3 times less respectively than NA and A activity, whereas in the caudal mesenteric ganglion, DA is 50 times more active than NA as regards ability to inhibit cholinergic conduction. The effects of DA and NA in the superior cervical ganglion are abolished by dihydroergotamine, phentolamine, and haloperidol, but not by tropaphen and chloropromazine. In the caudal mesenteric ganglion the inhibitory effect of NA is reduced by phentolamine, dihydroergotamine, and chlorpromazine but not by haloperidol. Conversely, haloperidol and chlorpromazine reduced the inhibitory effect of DA on cholinergic conduction in the caudal mesenteric ganglion, whereas phentolamine, dihydroergotamine, and deseryl were ineffective. It is postulated that the high level of development of the dopaminergic mechanism of inhibition of cholinergic conduction in the caudal mesenteric sympathetic ganglion may lie at the basis of DA-induced dilatation of mesenteric and renal blood vessels and the hypotensive action of DA.