Lesions of the anteroventral third ventricle region (AV3V) disrupt cardiovascular responses to an elevation in core temperature

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 288; no. 6; pp. R1783 - R1790
• Main Authors: Whyte, Douglas G, Johnson, Alan Kim
• Format: Journal Article
• Language: English
• Published: United States 01.06.2005
• Subjects: Animals; Blood Proteins - metabolism; Body Temperature - physiology; Hematocrit; Hemodynamics - physiology; Hypothalamus - physiology; Male; Osmolar Concentration; Preoptic Area - physiology; Rats; Rats, Sprague-Dawley; Salivation - physiology; Sodium - blood; Third Ventricle - physiology; Ultrasonography, Doppler, Transcranial; Vascular Resistance - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00524.2004

Departments of 1 Physiology and Biophysics, Psychology, Pharmacology, Exercise Science, and 2 the Cardiovascular Center, University of Iowa, Iowa City Submitted 2 August 2004 ; accepted in final form 7 January 2005 Blood flow is redistributed from the viscera to the periphery during periods of heat stress to maximize heat loss. The heat-induced redistribution of blood flow is strongly influenced by nonthermal inputs such as hydration status. At present, little is known about where thermal and nonthermal information is integrated to generate an appropriate effector response. Recently, the periventricular tissue that surrounds the anteroventral third ventricle (AV3V) has been implicated in the integration of thermal and osmotic information. The purpose of the present study was to determine the effects of electrolytic lesions of the AV3V on the cardiovascular response to a passive heat stress in unanesthetized, free-moving male Sprague-Dawley rats. Core temperature was elevated at a constant rate of 0.03°C/min in sham- and AV3V-lesion rats using an infrared heat lamp. Changes in mesenteric and hindquarter vascular resistance were determined using Doppler flow probes, and heat-induced salivation was estimated using the spit-print technique. The rise in mean arterial pressure (MAP), heart rate (HR), and mesenteric resistance in response to elevations in core temperature were all attenuated in AV3V-lesion rats; however, hindquarter resistance was unaffected. Heat-induced salivation was also diminished. In addition, AV3V-lesion rats were more affected by the novelty of the experimental environment, resulting in a higher basal core temperature, HR, and MAP. These results indicate that AV3V lesions disrupt the cardiovascular and salivatory response to a passive heat stress in rats and produce an exaggerated stress-induced fever triggered by a novel environment. thermoregulation; mesenteric resistance; Doppler flowmetry; salivation; novel environment Address for reprint requests and other correspondence: A. K. Johnson, Dept. of Psychology, Univ. of Iowa, 11 Seashore Hall E., Iowa City, IA 52242-1407 (E-mail: alan-johnson{at}uiowa.edu )