Conscious rats susceptible to dietary obesity have impaired reflex
bradycardia and enhanced norepinephrine sensitivity .
Bu[tilde]nag, Ruben D., Molly Meyer, Nichole Vansell, and Laszlo
Kerecsen.
Department of Pharmacology, Toxicology and Therapeutics, College of
Health Sciences and Hospital, University of Kansas Medical Center,
Kansas City, Kansas 66160
APStracts 3:0082R, 1996.
Male Sprague-Dawley rats fed a condensed milk diet were classified as
either "obesity susceptible" (OS) or "obesity
resistant" (OR) based on body weight increases attained after 12
weeks. Overall caloric intake in OS rats was higher than in chow-fed
controls, and OS rats were heavier than chow-fed controls or OR rats.
There were no significant differences in blood glucose, serum
insulin, ventricular weight, basal blood pressure or heart rate.
Pressor responses recorded after combined blockade with atropine and
propranolol to eliminate reflex effects, were identical for
vasopressin, but those to norepinephrine were larger in OS than in OR
rats while those to angiotensin were larger in OS than in control
rats. When baroreflex sensitivity was assessed using intravenously
infused sodium nitroprusside or phenylephrine to alter systemic
arterial pressure, differences in reflex tachycardia were equivocal,
but reflex bradycardia was clearly inhibited in OS rats. These
results show that although basal blood pressure was unaffected in OS
rats, their impaired reflex bradycardia along with enhanced pressor
responsiveness to norepinephrine could predispose them to subsequent
development of hypertension.
Received 31 August 1995; accepted in final form 26 February 1996.
APS Manuscript Number R545-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 20 March 96