QUINPIROLE-INDUCED ALTERATIONS OF TAIL TEMPERATURE APPEAR AS HYPERALGESIA IN THE RADIANT-HEAT TAIL-FLICK TEST

Several reports in the recent literature argue both for and against th e importance of alterations of tail-temperature in the outcome of the tail-flick test. The data we present here support the assertion that d rug-induced changes of tail-temperature may have a highly significant effect on tail-flick latency independent of drug-induced changes in no ciception. We previously reported that peripherally administered injec tions of the dopamine agonist, quinpirole, produce significant reducti ons in the latency of response in the tail-flick test. This present wo rk confirms our earlier findings; however, it indicates that the appar ent hyperalgesia is an artifactual function of quinpirole-induced incr eases in tail temperature. Quinpirole (0.1-1.0 mg/kg IP) produced sign ificant (p < 0.001), dose-dependent, and highly correlated increases i n tail temperature and decreases in tail-flick latency 15 min followin g injection. When controls for the change in tail temperature were app lied, there was no distinguishable effect of the drug on tail-flick la tencies. Sixty minutes following the administration of quinpirole ther e was no observable effect of the drug on either tail-temperature or t ail-flick latency. The results of this study indicate that a) peripher ally administered quinpirole has no effect on nociception as measured in the tail-flick test apart from its ability to alter tail temperatur e; and b) alterations in tail temperature may significantly after the outcome of the tail-flick test. (C) 1998 Elsevier Science Inc.