Modification of arterial blood pressure in rats following microinjection of drugs into the posterior hypothalamus

Abstract

Microinjections of histamine, norepinephrine or several cholinergic substances into the posterior hypothalamus of rats resulted in various effects on arterial blood pressure. Centrally injected histamine and norepinephrine produced an immediate rise in blood pressure. Carbachol usually produced a hypotensive response but on occasion a delayed rise in blood pressure or an immediate fall followed by a rise was observed. Pronounced changes in respiratory rate accompanied the rise in arterial blood pressure. The hypotensive response, which was also produced by acetylcholine and oxotremorine (a muscarinic agent) but not by nicotine, was mediated both centrally and peripherally by muscarinic mechanisms. Eserine, which produces a rise in blood pressure following systemic administration, caused a similar effect upon injection into the hypothalamus.