EFFECTS OF GANGLION- AND PARASYMPATHETIC-BLOCKING DRUGS UPON THE PRESSOR RESPONSE ELICITED BY ELEVATION OF THE INTRACRANIAL FLUID PRESSURE

¹ Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas

The effects of the ganglion-blocking drug, chlorisondamine, and the parasympatholytic drugs, atropine and valethamate, upon the neurogenic vasoconstriction elicited by elevation of the intracranial fluid pressure have been studied by use of the modified major vessel occlusion technique in dogs anesthetized with pentobarbital sodium. The results of these studies have shown that : 1) the administration of 1.0 mg/kg of chlorisondamine chloride reduces the amount of vasoconstriction which may be elicited by increase in the intracranial fluid pressure, but will not totally block the response; and 2) the administration of either 1.0 mg/kg of atropine or 50.0 µg/kg of valethamate following the administration of chiorisondamine will produce a further blockade of the vasoconstrictor response. The blockade obtained after the combination of a ganglion-blocking drug and a parasympathetic-blocking drug is almost total, and is approximately equivalent to the blockade produced by total spinal anesthesia. It has been concluded from these results that ganglion-blocking drugs do not totally block all physiologic transmission and that an additional sympathetic transmission, apparently ganglionic in nature, sensitive to parasympathetic drugs, exists.