BACKGROUND Brain corticotropin-releasing factor (CRF) is involved in stress-induced accelerated colonic transit. Brain sites of action of CRF to stimulate colonic transit were investigated in conscious fed rats. METHODS Bilateral guide cannulae were chronically implanted into the paraventricular nucleus of the hypothalamus (PVN) or central amygdala for peptide microinjection and a catheter into the proximal colon to measure colonic transit. RESULTS CRF (0.6 nmol/rat) injected into the PVN reduced colonic transit time by 84% and stimulated fecal pellet output 20-fold, whereas CRF injected into sites outside of the PVN or the central amygdala had no effect. CRF stimulatory action was prevented by chlorisondamine, and atropine methyl nitrate but not by bretylium. The stress of avoiding water by standing on a small cube reduced colonic transit time by 75% and increased fecal output by 7-fold. Bilateral microinjection of CRF antagonist, alpha-helical-CRF, into the PVN abolished the colonic response to stress. The CRF antagonist had no effect on basal colonic transit time in nonstressed rats. CONCLUSIONS Psychological stress-induced stimulation of colonic motor function in fed rats involves CRF pathways in the PVN.