Gaba-ergic mechanisms in the caudal ventrolateral region of the cat medulla regulating vascular tonus and cardiac activity

Abstract

In acute experiments on anesthetized cats data are obtained attesting to the fact that injections of GABA (0.5–50 µmoles/liter) into neuronal structures of the caudal ventrolateral medulla (CVLM) are accompanied by the development of hypertensive reactions caused by an increase in spontaneous activity in the sympathetic fibers of the renal and inferior cardiac nerves. An asymmetry is discovered in the realization of the inhibitory chrono- and inotropic influences on the heart emanating from the region investigated. Blocking of the GABA receptors with bicuculline (0.2–5.0 µmoles/liter) causes a sharp drop in the level of the systemic arterial pressure, a decrease in the strength and frequency of cardiac contractions, and a falling-off of the background activity in the peripheral symphathetic nerves. The findings suggest that the sympathoinhibitory CVLM neurons are under the constant inhibitory control of the GABA-ergic neurons.