The influence of age and drugs on the thermoregulatory behaviour of rats.

A method is described which allows to measure thermoregulatory effective conditioned behaviour in rats. This method makes it possible to vary the preset ambient temperature (Ta) in a wide range. The results only deal with subnormal Ta (normal housing temperature 23 degrees C). Rats are able to acquire a conditioned behaviour additional to inborn behaviour which is adequate to contribute to thermal homoeostasis. Exposed to -4 degrees C adult animals adjusted their mean Ta to +4 degrees C, old animals to +8 degrees C. A dose of 40 micromol/kg Phentolamine caused adult rats to adjust mean temperature to +9 degrees C, old rats to +13.5 degrees C. But even this increased behavioural activity did not prevent the hypothermic effect of the drug totally. Core temperature in adult animals dropped by 0.8 degrees C, in old animals by 1.4 degrees C.