Caloric effects of hypothalamus on rabbit's skin

ABSTRACT

The function of the thermoregulatory center of brain in regulating the process of heat exchange in rabbit's ear has been investigated in this work. Rabbits were stereotaxically implanted with water perfused thermodes in the brain to heat the hypothalamic thermoregulatory center. The normal hypothalamic temperature was found to be about 38.4 degree. This temperature maintains at that level despite the changes of the ambient temperatures due to a number of thermoregulatory mechanisms. One of these mechanisms is the role of ear pinna in varying the blood flow rate by constriction or dilation of the ear vessels. The work suggests that if the hypothalamic temperature is altered, a prominent response is achieved. The rise in ear temperature as a result of hypothalamus heatness seems to level off at higher temperatures. This may indicate a sort of saturation of the vasomotor system. This is a result of maximum dilation of blood vessels which maximizes the blood flow rate. This maximum dilation is found to be occurred at a hypothalamic temperature of 41-42 degree