Tail pinch induced consummatory behaviors are associated with analgesia

Pinching the tail of a rat results in a set of consummatory behaviors including chewing, eating and licking. In the present study, the effect of tail pinch on pain thresholds was evaluated using the hot-plate and writhing tests. Continuous tail pinch resulted in chewing and markedly lengthened the latency to hind-paw licking and jumping (hot-plate test) when compared with control rats and totally eliminated writhing behaviors. Tail pinch (which induced chewing) for one minute prior to the analgesic testing also prolonged the latency of hot plate-induced behaviors and suppressed the number of writhing behaviors. Naloxone reversed the tail pinch induced analgesia as measured by the hot-plate test, but did not reverse tail pinch-induced analgesia as measured by the writhing test.