Effects on cats of conductive hypothalamic cooling.

Conductive heating in the physiological range of sites in the anterior hypothalamus of the anesthetized cat caused a fall in rectal temperature and inhibition of shivering. Excessive heating caused also cutaneous vasodilatation, bradycardia and transient loss of nociceptive reflexes. Cooling at the same sites caused a rise in rectal temperature but did not cause shivering or cutaneous vasoconstriction. Heating of the posterior hypothalamus in the physiological range was associated with a slight rise in rectal temperature, and cooling with a slight fall. Changes in autonomic and somatic activity were rarely seen in association with such heating and cooling. In chronic preparations heating and cooling of sites in the anterior hypothalamus caused appropriate vasomotor and postural changes, whereas heating and cooling of sites in the posterior hypothalamus did not. It is concluded that receptors for both heat and cold are located in the anterior hypothalamus but probably not in the posterior hypothalamus.