Neuropeptide Y in the paraventricular nucleus of the hypothalamus stimulates colonic transit by peripheral cholinergic and central CRF pathways

There is evidence suggesting that neuropeptide Y (NPY) as well as corticotr opin-releasing factor (CRF) in the paraventricular nucleus of the hypothala mus (PVN) are involved in the CNS regulation of gastrointestinal (GI) funct ion. We studied the effects of NPY or Y1-and Y2-receptor agonists microinje cted into the PVN on colonic transit. Microinjection of NPY into the PVN at doses of 0.15-1.5 mu g decreased the colonic transit time of conscious rat s up to 49%. Pretreatment with the peripherally acting cholinergic antagoni st atropine methyl nitrate (0.1 mg kg(-1) i.p.) blocked the NPY into PVN-in duced effect on colonic motor function.The agonist of the Y1-receptor, NPY( Leu31, Pro34), as well as the Y2-receptor agonist, NPY(13-36), dose-depende ntly decreased colonic transit time when microinjected into the PVN (0.05, 0.15 and 0.5 mu g). However, the Y1-receptor agonist was more effective. In tracerebroventricular (ICV) application of the CRF-receptor antagonist, alp ha-helical-CRF9-41 (50 mu g/rat), blocked the NPY effect in the PVN on colo nic motor function. In conclusion, stimulation of colonic transit by NPY ac ting in the PVN was observed. The PVN is more sensitive to agonists acting on the Y1- than on the Y2-receptor to mediate stimulation of propulsive col onic motility. The effect of NPY in the PVN on colonic motor function depen ds on central CRF and peripheral cholinergic pathways.