EVIDENCE FOR AN INDIRECT CHOLINERGIC REGULATION OF BLOOD-FLOW IN THE HYPOTHALAMUS OF CONSCIOUS RABBITS

The effects of methacholine, atropine and adrenoceptor blockade on hypothalamic blood flow (HBF) were measured in conscious rabbits. A dose of 1 μg methacholine increased HBF while smaller and larger doses had no significant effect. The vasodilatation induced by methacholine was blocked by atropine and by chemical sympathectomy of the hypothalamus with 6‐hydroxydopamine. The vasodilatation was reversed by propranolol but was not affected by phenoxybenzamine. These results suggest that the vasodilator action of muscarinic receptor agonists on hypothalamic resistance vessels depends upon the integrity of a noradrenergic system, and is mediated via β‐adrenoceptors. 1979 British Pharmacological Society