CRF in the Paraventricular Nucleus of the Hypothalamus Stimulates Colonic Motor Activity in Fasted Rats

The influence of corticotropin releasing factor (CRF) microinjected into the paraventricular nucleus of the hypothalamus (PVN) on colonic motility was investigated in conscious, fasted rats. Rats were chronically implanted with a bilateral guide cannula into the PVN and a catheter into the proximal colon to record motor activity manometrically. Microinjection of CRF (0.6 nmol/rat) into the PVN increased both phasic and tonic motor activity in the proximal colon. Atropine sulfate (1 mg/kg, IP) completely abolished the colonic motor response to CRF. Microinjection of CRF (0.6 nmol/rat) into sites outside of the PVN did not modify colonic motor activity. These data show that CRF acts in the PVN to stimulate tonic and phasic motor activity in the proximal colon. Corticotropin releasing factor action is site specific and mediated through cholinergic pathways.