Sequential changes in regional distribution of blood in Eptesicus fuscus (big brown bat) during arousal from hibernation.

Abstract

Heart rates were studied in deeply hibernating and in arousing bats (Eptesicus fuscus). Values range from an average of 12 beats/min in deep hibernation to an average of 800 beats/min during peak arousal.Body temperatures were recorded. Arousing bats develop the "usual" anteroposterior temperature gradient.The distribution of blood was determined (Sapirstein method), and capillary organ blood-flow rates were approximated in deeply hibernating, in arousing, and in postarousal bats.The study indicates that, after the initiation of arousal, there is a redistribution of blood such that capillary blood-flow rates in organs of the anterior body rise more rapidly than do those in organs of the posterior body. A higher metabolic requirement for oxygen by brown adipose tissue as compared to other tissues, and the relatively high rate of heat production by brown fat, are thought to be largely responsible for this "shunting" of blood to anterior body regions during early arousal.