MUSCARINIC INVOLVEMENT IN VASCULAR AND ADRENAL-MEDULLARY RESPONSES TOSPLANCHNIC NERVE-STIMULATION IN CONSCIOUS CALVES

Stimulation of the peripheral end of the right splanchnic nerve (4 Hz for 10 min) in the presence of hexamethonium caused a small but signif icant rise in mean aortic blood pressure which was subsequently abolis hed by atropine. There were also small but significant increases in th e outputs of catecholamines, [Met(5)]-enkephalins and corticotrophin r eleasing factor (CRF) from the right adrenal gland. The catecholamine response was roughly halved after atropine while the outputs of enkeph alins and CRF were unaffected. It is concluded that splanchnic sympath etic postganglionic neurones supplying the vasculature are completely blocked by cholinergic blockade whereas adrenal medullary responses pe rsist in an attenuated form.