Imaging of ventral medullary surface activity during blood pressure
challenges in awake and anesthetized goats.
Harper, Ronald M., David Gozal, Hubert V. Forster, Patricia J. Ohtake,
Lawrence G. Pan, Timothy F. Lowry, and David M. Rector.
Department of Neurobiology, University of California at Los Angeles
School of Medicine, Los Angeles, CA 90095-1763, Division of
Neonatology and Pediatric Pulmonology, Childrens Hospital Los
Angeles, University of Southern California School of Medicine, Los
Angeles, CA 90027, Department of Physiology, Medical College of
Wisconsin, Zablocki Veteran's Administration Hospital, Milwaukee, WI
53226 and Program in Physical Therapy, Marquette University,
Milwaukee, WI 53233-2269
APStracts 2:0213R, 1995.
We examined scattered light changes in a rostral ventral medullary
surface (VMS) area from 5 goats following blood pressure challenges
during waking and halothane anesthesia. Reflected 660 nm images were
digitized at 1/sec following baseline, intravenous saline, 5, 10, and
15 [mu]g/kg phenylephrine administration, or sodium nitroprusside
infusion sufficient to lower blood pressure by 50%. Phenylephrine
elicited a dose-dependent, blood pressure elevation during both
states, and a substantial transient reflectance increase (interpreted
as activity decline) during anesthesia, but only a minimal, long
latency, slow reflectance decrease (activity increase) during waking.
Sodium nitroprusside elicited lowering of blood pressure and
decreased reflectance in the rostral site during anesthesia. The
magnitude of the reflectance change to depressor challenge increased
30%, and the onset latency shortened during waking. Isolated regions
of enhanced reflectance changes appeared during both challenges.
Activity in this rostral VMS site differentially responds to blood
pressure elevation or lowering, and state markedly alters the
responses. We speculate that VMS responses to depressor challenge
represent reflex activation of respiratory regions.
Received 21 December 1994; accepted in final form 19 July 1995.
APS Manuscript Number R724-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.