New apparatus for studying behavioral thermoregulation in rats.

The operant system described here contains a box that can be convectively heated or cooled. A rat moves freely in the box. Its location is monitored photoelectrically while its deep body temperature is monitored by a telemetry system. In heat-escape experiments, hot air (40 degrees C) flows through the box. When the rat enters a reward zone the air source is switched and cold air (0 degrees C) flows through the box for a given period (30 s). Conversely, in cold-escape experiments cold air flows through the box and when the rat enters the reward zone the air source is switched to a warm one. Experiments show that rats quickly learn to stay near the reward zone and move in and out of it periodically. This system is based on behavior more natural than the frequently used lever-pressing response, and has many advantages for use in studies involving behavioral thermoregulation.