Skin or hypothalamus cooling: a behavioral choice by rats.

Rats were chronically implanted with a hypothalamic thermode. After recovery the thermode was heated and the rats were exposed to 4 ambient temperatures (Ta) 20, 30, 35 and 40 degrees C. For each Ta they were subjected to 3 conditions: (1) they could press a bar which provided them with a cool wind; (2) they could press a bar which cooled the hypothalamic thermode; and (3) both bars were active and the rat could press either one. Skin, hypothalamic, and rectal temperatures were recorded at the same time. The results indicate that when rats had either only or by choice access to the lever that cooled their hypothalamus, they used it in such a way as to prevent their hypothalamus from overheating. A lower priority was given to the maintenance of skin temperature.