"CARDIOVASCULAR" NEURONES IN BRAIN STEM OF CAT

Abstract

Systematic exploration with microelectrodes of the brain-stems of 21 cats revealed in 53 instances the presence of neurones which consistently modified their rate of discharge (i) during drug-induced (noradrenaline and histamine, 1-3 Ug. i. v.) arterial pressure fluctuations, or (ii) synchronously with some portion of a Mayer''s wave, or (iii) during occlusion of a common carotid artery. Such units, called "cardiovascular neurones", did not discharge in rhythmic bursts but exhibited a continuous irregular form of discharge. Of the 53 cardiovascular neurones found, 12 units (called "population one neurones") showed an increase in discharge rate when arterial pressure rose and a decrease when arterial pressure fell or when a common carotid artery was briefly occluded. The remaining 41 units (called "population two neurones") behaved in the opposite way. Cardiovascular neurones were found both in the medulla and in the pons, more often within medial structures. Population-one and population-two neurones were not found segregated but were intermingled within the same region.