Stress-induced visceral hypersensitivity to rectal distension in rats: role of CRF and mast cells

Background: psychological factors have long been implicated in the aetiology of irritable bowel syndrome often associated with abdominal pain. This work was designed to study, in rats, the influence of partial restraint stress on the abdominal cramps induced by rectal distension and to determine the role of corticotropin releasing factor (CRF) and mast cells degranulation in this response. Methods: abdominal contractions were electromyographically recorded. Thirty minutes after stress or intracerebroventricular CRF, rectal distension was performed by inflation of a balloon (0.4-1.2 mL). alpha-helical CRF9-41 or doxantrazole were administered centrally (15 min) and intraperitoneally (30 min), respectively, before stress. Histamine release and the number of mast cells were determined in colonic pieces from stressed and control rats. Results: stress and CRF enhanced the number of abdominal cramps evoked by rectal distension without affecting rectal compliance. alpha-helical CRF9-41 and doxantrazole antagonized the stress and CRF-induced enhancement of abdominal cramps. Stress increased the colonic histamine content whereas the number of colonic mast cells was unchanged. Conclusions: stress enhances abdominal contractions in response to rectal distension in rats via pathways involving central CRF and intestinal mast cells.