FURTHER STUDIES OF SYMPATHETIC ACTIONS OF ANAESTHETICS EN INTACT AND SPINAL ANIMALS BY

Sympathetic activity was recorded before and during administration of various anaes-thetic drugs, in animals of various species ventilated mechanically and given chloralose. Intravenously injected sodium bicarbonate solutions raised the discharge level transiently. Thiopentone and pentobarbitone depressed the discharge, as did methoxyflurane and Ethrane; hypotension with Ethrane was not directly attributable to central sympathetic inhibition. The activity was increased markedly by diethyl ether and chloroform, to a lesser extent by trichloroethylene, and erratically by teflurane. An increase in sym-pathetic discharge usually occurred on the addition of nitrous oxide to those agents which lowered activity. Ether caused significant preganglionic sympathetic excitation in cats subsequent to cervical cord transection. In recent laboratory studies, we have described central sympathetic excitation by cyclopropane (Price et al., 1969), and a lack of correlation be-tween preganglionic discharge and arterial pres-sure during halothane administration (Millar e