Role of ATP in the Mechanisms Underlying Intestinal Afferent Sensitivity to Hydrogen Sulphide

group (n=14) received no injection.The 2 nd CRD was monitored immediately (day 4) and the 3 rd CRD, 24 h after the last WAS (day 5).The VMR to CRD after WAS was expressed as percentage of the respective baseline values at different pressures of CRD.Data were analyzed using two-way ANOVA followed by a multiple comparison Bonferroni post-hoc test.Results: Immediately after the 1h exposure to WAS, on day 4, non-injected male and female rats exhibited visceral analgesia at 40 mmHg (p<0.05).Saline or naloxone injected sc before each WAS enhanced the visceral analgesia in both sexes in comparison to noninjected rats (analgesic response at 40 and 60 mmHg).On day 5, 24h after the last session of stress, the VMR was back to baseline values in all non-injected and injected male and female rats, except in females injected with naloxone which exhibited an analgesia at 60 mmHg (74.8±11.9vs 100.0±0.0 %, p<0.05).Conclusions: When monitored non-invasively, intermittent repeated exposure to a psychological stress induces an immediate naloxoneindependent visceral analgesia in male and female rats.Repeated sc injections potentiate the immediate analgesic response suggesting that the concomitant somatic noxious stimuli may exert heterotopic analgesic effects.The sex-dependent delayed restoration of the VMR to baseline values by naloxone indicates an opioid-dependent component in females' stressinduced visceral response.