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 fo r 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 hormo nal disturbances following brief but intense stress. Male and female Wistar rats were fitted with chronic electrodes on proximal colon and given eithe r a 15-minute session of foot shocks or no shocks. Two weeks later, rats we re exposed to two different novel stressful challenges in the home cage: an electrified prod (day 14) and an 85 dB noise stressor (day 15). Digitalise d colonic myoelectric spike burst activity was quantified automatically. Be haviour during prod and noise exposure was scored blindly from videotape. R esting plasma hormone concentrations at the end of the study were determine d by radio-immune assay. Following prod stress on day 14, both male and fem ale preshocked rats showed a greater increase in colonic spike burst freque ncy than controls, but similar behaviour, and the dynamics of colonic motil ity 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 female s to show increased noise-induced immobility. Preshocked rats also had lowe r levels of plasma free thyroxine. While both male and female rats show lon g-term stress-induced colonic sensitisation and hormonal changes, females s how a different activation pattern of colonic motility, and may be more vul nerable for altered behavioural reactivity, following stress.