Excitability changes in vasomotor areas of the brain stem following D-tubocurarine

Abstract

Cardiovascular responses to electrical stimulation of the medulla and hypothalamus have been studied before and after administration of d-tubocurarine. The drug was administered intravenously (100–150 gamma/kg) intracarotid (100–150 gamma/kg) and by direct microinjection into the medullary vasomotor area (3–15 gamma total dose). The possibility of autonomic ganglia or effector blockade was ruled out. Excitability of the medullary vasomotor area to electrical stimulation was depressed following injection of d-tubocurarine by any of the three routes. Partial to total elimination of pressor responses has been observed, as well as reversal from a pressor to a depressor response. Cardiac slowing resulting from stimulation of the dorsal vagal nucleus is abolished or greatly decreased by intracarotid injection of 150 gamma/kg of d-tubocurarine. Doses of this drug which depress the medulla had relatively little effect on similar cardiovascular responses elicited by stimulation of the hypothalamus.