Peripheral peptide YY inhibits propulsive colonic motor function through Y2 receptor in conscious mice
Peptide YY (PYY) antisecretory effect on intestinal epithelia is well established, whereas less is known about its actions to influence colonic motility in conscious animals. We characterized changes in basal function and stimulated colonic motor function induced by PYY-related peptides in conscious mice. PYY3–36, PYY, and neuropeptide Y (NPY) (8 nmol/kg) injected intraperitoneally inhibited fecal pellet output (FPO) per hour during novel environment stress by 90%, 63%, and 57%, respectively, whereas the Y1-preferring agonists, [Pro34]PYY and [Leu31,Pro34]NPY, had no effect. Corticotrophin-releasing factor 2 receptor antagonist did not alter PYY3–36 inhibitory action. PYY and PYY3–36 significantly reduced restraint-stimulated defecation, and PYY3–36 inhibited high-amplitude distal colonic contractions in restrained conscious mice for 1 h, by intraluminal pressure with the use of a microtransducer. PYY suppression of intraperitoneal 5-hydroxytryptophan induced FPO and diarrhea was blocked by the Y2 antagonist, BIIE0246, injected intraperitoneally and mimicked by PYY3–36, but not [Leu31,Pro34]NPY. PYY3–36 also inhibited bethanechol-stimulated FPO and diarrhea. PYY3–36 inhibited basal FPO during nocturnal feeding period and light phase in fasted/refed mice for 2–3 h, whereas the reduction of food intake lasted for only 1 h. PYY3–36 delayed gastric emptying after fasting-refeeding by 48% and distal colonic transit time by 104%, whereas [Leu31,Pro34]NPY had no effect. In the proximal and distal colon, higher Y2 mRNA expression was detected in the mucosa than in muscle layers, and Y2 immunoreactivity was located in nerve terminals around myenteric neurons. These data established that PYY/PYY3–36 potently inhibits basal and stress/serotonin/cholinergic-stimulated propulsive colonic motor function in conscious mice, likely via Y2 receptors.