| The aim of this project was to determine the effect of heating to physiologically relevant temperatures above 37;To determine the mechanism for this heating-induced hyporesponsiveness, vascular smooth muscle and reflex neural responses to vasoactive agents were investigated. Vascular reactivity was assessed in rat thoracic aortic and mesenteric arterial ring segments by generating concentration-response curves to vasoconstrictor and vasodilator agents at 37 and 41;Reflex neural and hemodynamic responses to vasoactive agents were measured in conscious rats during hyperthermia. The hemodynamic responses to phenylephrine were blunted at 41.5;Collectively, these data demonstrate that the hemodynamic responses to vasoconstrictor agents are blunted during heating. This attenuation is not due to a direct effect of temperature on adrenoceptor function, but can be attributed, in part, to enhanced baroreflex-mediated withdrawal of sympathetic neural outflow to the viscera. |
