Gender differences in predator induced pain perception in rats.

Pain is an unpleasant sensation. It warns the living being about the impending damage to the tissues. The perception of pain is influenced by physical and psychological factors. The impact of chronic intermittent psychological stress on pain perception and the differences in antinociceptive responses have been studied in male and anestrous female albino rats. Fifteen rats in each group were subjected to psychological stress, by exposing them to their natural predator--cat, for a duration of 20 min daily for 12 consecutive days. Tail flick response latency to radiant heat was used as a measure to evaluate pain perception. It was observed that both the groups had a relatively high pain threshold at the beginning of exposure schedule due to the modulation of opioid analgesic system by the higher level of circulating testosterone in males and low level of estrogen in anaestrous females. However, the threshold for pain perception showed a gradually declining trend in both the groups over the next 11 days to reach the control values. This increase in sensitivity to pain or decreased pain threshold could be attributed to the phenomenon of habituation.