We investigated chronic psycho-social stress effects on stress-related parameters and on pathohistological changes in the murine colon. Moreover, we aimed to reveal the involvement of adrenal glucocorticoids in chronic stress effects. Chronic subordinate colony housing (CSC, 19 days) resulted in reduced body weight gain, thymus atrophy, adrenal hypertrophy, increased plasma norepinephrine, and increased anxiety. With respect to the time course of CSC effects, CRH mRNA in the hypothalamic paraventricular nucleus, light phase corticosterone and tyrosin hydroxylase (TH) expression in colonic tissue were found to be increased, whereas TH expression in the locus coeruleus was found to be decreased on day 2 of CSC; these parameters returned to control levels thereafter. Nevertheless, after 19 days of CSC exposure, the adrenal corticosterone responses in vivo and in vitro, and glucocorticoid sensitivity of isolated splenic cells were found to be decreased. Importantly, in CSC mice a significant histological damage of the colon was found beginning on day 14 of CSC exposure. Additionally, pro- and anti-inflammatory cytokine secretion by mesenteric lymph node cells was increased after CSC exposure. Adrenalectomy (ADX) before CSC at least partially prevented these chronic stress effects as reflected by less increase in pro-inflammatory cytokine secretion and an equal histological damage score in ADX compared with SHAM operated CSC mice.

In conclusion, chronic exposure to CSC alters relevant neuronal, neuroendocrine and immune functions which could be directly or indirectly involved in the damage of the histological integrity of the colon comparable with that seen during the development of the colitis.