The effect of morphine on core and skin temperature in rats

The temperature of the tail skin is an important factor determining tail-flick latency to noxious radiant heat in rats and mice. The temperature of the skin may also be important in determining the behavioural response in the formalin test. Morphine in low and moderate doses strongly affected the core and tail skin temperatures, preventing the increase in tail skin temperature normally observed during testing. For the correct interpretation of the results of several tests of nociception, it is important to know how treatment influences the temperature of the skin, to be able to correct for this confounding factor.