24-Hour Control of Body Temperature in Rats. 1. Integration of Behavioral andAutonomic Effectors

摘要

Some studies suggest that the nocturnal elevation in core temperature T(sub C) ofthe rat is mediated by an elevation in the set point. The role of set point can be assessed if behavioral effectors are measured simultaneously with other thermoregulatory effectors and T(sub c) of the rat is mediated by an elevation in the set point. The role of set point can be assessed if behavioral effectors are measured simultaneously with other thermoregulatory effectors and T(sub c) over a 24-h period. Selected ambient temperature (ST(sub a)) and motor activity (MA) were measured in rats housed in a temperature gradient system with a 12:12-h photoperiod (lights on 0600 h). T(sub c) and heart rate (HR) were monitored by telemetry. During the light phase, ST(sub a), T(sub c) HR, and MA were relatively stable with values 29.0 deg C, 37.1 deg C, 310 beats/min, and 1-2 m/h, respectively. During the light-to-dark transition there were abrupt elevations in T(sub c), HR, and MA but no change in ST(sub a). ST(sub a) decreased during the dark phase and reached a nadir of 23 deg C at 0500 h. All variables recovered to basal levels within 3-4 h after the onset of the light phase. Overall, autonomic effectors control the elevation in T(sub c) during the onset of the dark phase while behavioral effectors have little if any role.