THE EFFECTS OF ACUTE AND REPEATED RESTRAINT STRESS ON THE NOCICEPTIVERESPONSE IN RATS

The effects of acute and repeated restraint stress on nociception, as measured by the tail-flick latency, were studied in adult male and fem ale rats. After the exposure to a single restraint session, both male and female rats presented an increased latency in the tail-flick test. On the other hand, chronically stressed females presented a performan ce similar to the control group, whereas chronically stressed male rat s responded to restraint with a decrease in the tail-flick latency. Th is response could be determined by the chronic treatment itself or by the restraint done just before the measurement. Thus, the effect of ch ronic stress upon basal tail-flick latency was evaluated. In male rats , this latency was significantly decreased in the stressed animals com pared with the control group. In female rats, no difference between th ose groups was observed. Therefore, the results suggest that: (a) acut e restraint stress induces an analgesic response in both male and fema le rats, and (b) there is a gender-specific nociceptive response induc ed by repeated restraint stress with a hyperalgesic effect in response to stress only in males. (C) 1998 Elsevier Science Inc.