Effect of heating & cooling the hypothalamus on behavioral thermoregulation in the pig.

1. Pigs were trained to push a switch with their snouts in order to obtain a short burst of infra-red heat on the skin.2. When the preoptic region of the hypothalamus was cooled by means of an implanted thermode, the rate at which the heaters were turned on increased at environmental temperatures ranging from 0 to 25 degrees C. At 30 and 35 degrees C cooling sometimes had no effect.3. The preoptic region was warmed either by means of a thermode or using radio-frequency heating from implanted electrodes. Warming the preoptic region decreased the rate at which the infra-red heaters were turned on, but the effect was not as obvious as the increases observed during cooling.4. Pigs placed in a cold or neutral environment did not learn to push a switch in order to obtain radio frequency heating of the preoptic region.