THE TAIL-FLICK AND FORMALIN TESTS IN RODENTS - CHANGES IN SKIN TEMPERATURE AS A CONFOUNDING FACTOR

In the tail-flick test as well as in the late phase in the formalin te st skin temperature may in an important way influence the response. A reduced skin temperature may be misinterpreted as analgesia, and an in creased skin temperature as hyperalgesia. These effects and the mechan isms that cause them are discussed. It is of particular importance to be aware of these confounding factors when using drugs or making lesio ns that influence blood flow or temperature regulation. It is importan t that all variables influencing the test results are kept constant th roughout the experiment. This includes not only the ambient temperatur e, but also factors that may influence the vasomotor tone of the anima ls.