Sex differences in long-term stress-induced colonic, behavioural and hormonal disturbances.

Functional bowel disorders are more prevalent in women than in men, but the reason for this is unclear. Stressful experiences can increase the risk for or precipitate intestinal dysfunction. Using a model for long-term stress-induced sensitisation in rats, it was investigated whether male and female rats differ in susceptibility for long-term colonic, behavioural and hormonal disturbances following brief but intense stress. Male and female Wistar rats were fitted with chronic electrodes on proximal colon and given either a 15-minute session of foot shocks or no shocks. Two weeks later, rats were exposed to two different novel stressful challenges in the home cage: an electrified prod (day 14) and an 85 dB noise stressor (day 15). Digitalised colonic myoelectric spike burst activity was quantified automatically. Behaviour during prod and noise exposure was scored blindly from videotape. Resting plasma hormone concentrations at the end of the study were determined by radio-immuno assay. Following prod stress on day 14, both male and female preshocked rats showed a greater increase in colonic spike burst frequency than controls, but similar behaviour, and the dynamics of colonic motility differed between sexes. Following noise stress on day 15, only a small change in burst frequency was seen in all rats, but preshocked rats showed less self-grooming behaviour and there was a tendency for preshocked females to show increased noise-induced immobility. Preshocked rats also had lower levels of plasma free thyroxine. While both male and female rats show long-term stress-induced colonic sensitisation and hormonal changes, females show a different activation pattern of colonic motility, and may be more vulnerable for altered behavioural reactivity, following stress.