EFFECT OF CENTRAL INJECTIONS OF DOPAMINE ON CORE TEMPERATURE AND THERMOREGULATORY BEHAVIOR IN UNRESTRAINED RATS

The effect of restraint on core temperature changes induced by intrahypothalamic dopamine injection in conscious rats has been investigated. Central injections of dopamine (10 and 20 μg) produced a dose-related hypothermia in both restrained and unrestrained rats maintained at an ambient temperature of 17 ± 1°C. However the magnitude of the response in unrestrained rats was smaller than that in restrained rats. Using a test which measures the time a rat takes to escape from an imposed heat load it was found that rats receiving an intrahypothalamic injection of dopamine (20 μg) remained under the heat lamp for a significantly shorter time than vehicle-injected controls. As rats were leaving the heat source at a time when their core temperature was reduced, these results are interpreted as support for the hypothesis that dopamine exerts its influence on thermoregulation by lowering the setting of an internal thermostat. The ability of pimozide to block both the temperature and the behavioural responses suggests that dopamine receptors are involved. © 1979.