THE EFFERENT PATHWAY OF CHEMOREFLEX VASOMOTOR REACTIONS ARISING FROM THE CAROTID BODY

Abstract

Reflex vasomotor reactions resulting from the action of chemical agents at the carotid body are qualitatively the same in the sub-maxillary gland as in other body regions in the dog, e.g., NaCN elicits reflex vasoconstriction usually followed by vasodilatation and NaCOs elicits simple vasodilatation. In most individuals (9 of 11) cutting the cervical (vago) sympathetic trunk completely obliterated chemoreflex vasomotor reactions in the submaxillary gland even though the parasympathetic innervation (chorda tympani) remained intact and even when eserine was administered to potentiate any activity of this innervation. In one and possibly 2 of 11 animals, small reactions persisted after the vago-sympathetic trunk had been severed. It is believed that these reactions were mediated by aberrant fibers of the thoracico-lumbar autonomies. In all of the 4 dogs in which it was tried, sympathectomy removed all recognizable chemoreflex vasomotor reactions in the leg even though the dorsal root vasodilator innervation remained intact. It is concluded that in the dog, certainly in most individuals and probably in all, the thoracico-lumbar autonomic fibers constitute the sole efferent pathway for vascular reflexes originating at the carotid body.