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 the importance of alterations of tail-temperature in the outcome of the tail-flick test. The data we present here support the assertion that drug-induced changes of tail-temperature may have a highly significant effect on tail-flick latency independent of drug-induced changes in nociception. We previously reported that peripherally administered injections of the dopamine agonist, quinpirole, produce significant reductions in the latency of response in the tail-flick test. This present work confirms our earlier findings; however, it indicates that the apparent hyperalgesia is an artifactual function of quinpirole-induced increases in tail temperature. Quinpirole (0.1-1.0 mg/kg I.P.) produced significant (p < 0.001), dose-dependent, and highly correlated increases in tail temperature and decreases in tail-flick latency 15 min following injection. When controls for the change in tail temperature were applied, there was no distinguishable effect of the drug on tail-flick latencies. Sixty minutes following the administration of quinpirole there was no observable effect of the drug on either tail-temperature or tail-flick latency. The results of this study indicate that a) peripherally administered quinpirole has no effect on nociception as measured in the tail-flick test apart from its ability to alter tail temperature; and b) alterations in tail temperature may significantly alter the outcome of the tail-flick test.
Roane
D S
DS
Division of Molecular Pharmacology, School of Pharmacy, Northeast Louisiana University, Monroe 71209-0470, USA.
Bounds
J K
JK
Ang
C Y
CY
Adloo
A A
AA
D000704:Analysis of Variance; D000818:Animals; D018491:Dopamine Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced*; D008297:Male; D010147:Pain Measurement / Q000379:methods*; D019257:Quinpirole / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012881:Skin Temperature / Q000187:drug effects*; D013623:Tail
D018491:Dopamine Agonists; D019257:Quinpirole