CNS regulation of body temperature during hibernation.

HELLER, H. C., AND G. W. COLLIVER. CA’S regulation of body tembera t we during hiberna t ion. Am. J. Physiol. 227(3): 583-589. 1974.-The body temperature (Tb) of hibernating golden-mantled ground squirrels, Citellus lateralis, passively follows ambient temperature (Tft) down to some critical temperature below which metabolic heat production increases and the differential between 1‘1, and T:, increases. This paper demonstrates that such apparent thermoregulatory responses during hibernation are mediated by the central nervous system (CNS) regulator of Tl, located in the preoptic nuclei and the hypothalamus (POH). By heating and cooling the POH of hibernating ground squirrels, it was possible to elicit changes in metabolic heat production which can be described by the equation: Rr R,, = a (‘I&. T,,t); where Thy is POH temperature, T sct is the threshold POH temperature for activating the response in question, a is a proportionality constant, R, is the basal rate of the response when Tllv = Tsct, and Rr is the response rate elicited by a Tl,, below T,,t. For 10 response curves constructed for six animals, a! averaged -4.46 X 1 OB4 W g-1 OC-l and ranged from 2.79 X 1 Om4 to 6.48 X 1 OA4 W g-1 OC-! TpCt averaged 6.3OC and ranged from 1.2 to 12.5OC. The Qlo for the increase in a! from a Tsct, of 6°C: to a T,,,t, of 36OC (euthermia) is 2.5. It is hypothesized that the same populations of neurons are responsible for thermoregulation in euthermia and cleep torpor. The evolution of an adequate Q! for driving thermoregulatory responses when Tsct is very low during torpor may also have given rise to the extremely high cy values measured on euthermic ground squirrels.