Processing of vestibular, hindlimb and baroreceptor inputs by neurons in the caudal ventrolateral medullary reticular formation. Steinbacher, B. C., Jr., and B. J. Yates. Departments of Otolaryngology and Neuroscience, University of Pittsburgh, Pittsburgh, PA 15213
APStracts 3:0197R, 1996.
Lesions of the lateral medullary reticular formation caudal to the obex abolish vestibulo-sympathetic and somato-sympathetic responses; this area also contains neurons that mediate baroreceptor reflexes. Recordings were made from neurons in the caudal medullary reticular formation of cats that were decerebrate or anesthetized using [alpha]-chloralose/urethane to determine whether common neurons responded to electrical stimulation of vestibular and hindlimb afferents and had cardiac-related (i.e., baroreceptor) inputs. Many neurons in the ventrolateral portion of the caudal reticular formation received labyrinthine inputs, and they were interspersed with neurons that received baroreceptor signals. However, virtually none of the units received convergent baroreceptor and vestibular inputs, suggesting that separate pathways from the caudal ventrolateral medulla mediate baroreceptor and vestibulo-sympathetic reflexes. Furthermore, the neurons that received labyrinthine signals could not be antidromically activated from electrodes inserted into the rostral ventrolateral medulla, which is known to mediate vestibulo-sympathetic responses; thus, an indirect pathway must convey vestibular inputs from the caudal to rostral medullary reticular formation. Over 75% of both neurons with baroreceptor inputs and cells with vestibular signals responded to sciatic nerve stimulation, suggesting that more than one pathway from the caudal medulla may mediate somato-sympathetic responses. 

Received 5 January 1995; accepted in final form 6 May 1996.
APS Manuscript Number R7-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96