The influence of colonic temperature changes in anaesthetised rats on tail skin temperatures and repeated testing of tail-flick latencies.

Tail-flick (TF) response latencies were measured in pentobarbitone-anaesthetized rats and variations with time, body and tail temperatures and 5 tail stimuli positions analysed with a mixed model analysis of variance. Variation with time was not significant. Highly significant differences (P < 0.001) were found between tail-flick latencies (TFLs) for tail temperatures and stimulus position. The most proximal tail position showed significantly different relationships for TFL with time and body temperature from other positions. The method described allows multiple TFLs to be measured in 1 animal with the potential of reducing the total number of animals in an experiment. Tail stimuli positions from proximal to distal sites showed a variation in response from 4.3 sec (95% CI: 4.2, 4.4) to 6.7 sec (95% CI: 6.6, 6.9). Rat tail stimulus position should therefore be standardised to allow reproducible measures of TFL and body temperature maintained within normal limits. TFLs were found to be abnormal at body temperatures above 39 degrees C.