We had shown that the mechanism of analgesia induced by swimming stress in Wistar males is closely related to stress, some of the relation to this mechanism with cortical hormones. The aims of this research is to study the sexual differences in the mechanism of analgesia induced by swimming stress in both male and female Wistar rats and the possibility of its relation with sexual hormones. The male and female show an increase in the threshold of pain as result of swimming stress (Swimming in the water during 3 minutes, with 16 C). The analgesia in the females was more important compared with males. The pretreatment with naloxone led to a partial inhibition of stress- induced analgesia in both sexes, but in males it was more important. The testectomized rats which exhibited a good response to stress induced analgesia were similar the control males. In contrast the stress induced analgesia in ovariectomized rats was not so evident as in the control females. The naloxone had partial inhibition stress induced analgesia in both sexes. Contrary to the male testectomaized rats which showed a similar response to the control rats due to the naloxone, the inhibition is more important in ovariectomized female rats than in control rats. On the other hand the male rats which were pretreated with eulexin (antiandrogen) and the females treated with anti estrogen (tamoxifen) while they were under swimming stress have similar response to the gonadectomized rats where the naloxone had partially reduced the stress- induced analgesia. In this group of rats similarly for the registered inhibition in the gonadectomized rats. These results showes a relation between swimming stress-induced analgesia in Wistar rats and sex. The females showed swimming stress-induced analgesia more than the males. Contrary to the dominance of the opioid mechanisms and the absence of the cooperation of the androgens in stress-induced analgesia in the males. The females presents analgesia which is carried by opioid and non-opioid mechanisms in close relation with ovarian estrogens.
Key Words: Swimming Stress, Analgesia, Sex Differences, Sexual Hormones, Gonadectomy, Naloxone, Antiandrogen, Antiestrogen