A tail withdrawal procedure for assessing analgesic activity in rhesus monkeys

Abstract

Rhesus monkeys were restrained in chairs from which their tails hung free so that their tails could be immersed into a thermos of water. Monkeys consistently kept their tails in 38-40[deg]C water for at least 20 sec, but withdrew them from 55[deg]C water in 1-4 sec. Tail withdrawal latencies from 55[deg]C water remained consistent over a period of 3 hr. Morphine produced dose-dependent increases in tail withdrawal latencies from 55[deg]C water, whereas pentobarbital, haloperidol, and phencyclidine did not increase tail withdrawal latencies except at doses that produced marked sedation.