Single Unit Responses to Catecholamines in the Nucleus Tractus Solitarii and Dorsal Motor Nucleus of the Vagus

Abstract

The nucleus tractus solitarii (NTS) and nucleus dorsalis motoris vagi (NDMV), located in the rostral dorsomedial medulla oblongata, have been implicated in the control of cardiovascular hemodynamics [1]. In the albino rat, the vast majority of baroreceptor afferents from the vagus nerve and, to some extent, the glossopharyngeal project to the medial subnucleus of the NTS, with the densest concentration of such nerve endings being found at the level of the obex [2]. While the neurotransmitter of these afferents has been identified as glutamate [3], considerable evidence indicates an important role for the biogenic amines, epinephrine, norepinephrine (NE), and dopamine (DA), in the processing and possible modification of barorecep-tive information at the NTS and NDMV [4]. For the most part, studies investigating the physiological role played by these catecholamines (CAs) in the central regulation of blood pressure have involved microinjections of the CAs into the NTS, while focussing on peripheral hemodynamic changes. In the present study, CAs were applied iontophoretically onto neurons within the medial NTS and the NDMV to gain insight into the action of these compounds at the cellular level.