Preganglionic discharge to the cardiovascular system in the comatose cat

¹ Masonic Medical Research Laboratory, Utica, New York

A technique for isolating and recording from single fibers in the thoracic spinal canal permits access to the entire preganglionic outflow of the thoracic spinal cord of the cat. In the cat rendered comatose by the selective destruction of the brain stem, there are two interchangeable patterns of impulse activity which reflect the level of systemic blood pressure. Periodic bursts of high-frequency discharge, synchronous with the respiratory cycle, are replaced by continuous activity when increased sympathetic discharge to the cardiovascular system is evoked by hypothalamic stimulation or by reflex mechanisms. The data suggest that impulse pattern as well as frequency of stimulation may be a factor of importance in the sympathetic organ response to direct stimulation of the innervating postganglionic nerve.

Key Words: vasomotor regulation • sympathetic fibers • Traube-Hering waves • rhythmic discharge • single fiber recordings

Submitted on April 4, 1963