title: Neuropeptide Y inhibits excitatory enteric neurons supplying the circular muscle of the guinea pig small intestine.
abstract: The effect of neuropeptide Y on the motor activity of the circular and longitudinal muscle of the guinea pig small intestine was investigated. Neuropeptide Y (0.3-30 nM) inhibited, in a concentration-dependent manner, the ascending enteric reflex contraction of the circular muscle; both the cholinergic and noncholinergic component of the ascending enteric reflex were suppressed. Neuropeptide Y also blocked nerve-mediated phasic contractions of the circular muscle, induced by dimethylphenylpiperazinium or ceruletide, and abolished the peristaltic movements of the small intestine. Nerve-mediated cholinergic and noncholinergic contractions of the longitudinal muscle, induced by electrical field stimulation, were only slightly depressed by neuropeptide Y. Further analysis showed that neuropeptide Y did not act directly on intestinal muscle but interrupted excitatory pathways of the enteric nervous system. The effect of neuropeptide Y did not involve activation of alpha-adrenoceptors, opioid receptors, or P1 purinoceptors or the release of endogenous factors stimulating these receptors. These findings suggest a possible physiologic role of neuropeptide Y as a nonnoradrenergic inhibitory transmitter involved in the enteric nervous control of intestinal circular muscle activity.
mesh_terms: D000818:Animals; D001030:Apamin / Q000494:pharmacology; D001285:Atropine / Q000494:pharmacology; D002108:Ceruletide / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006145:Guanethidine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000187:drug effects* / Q000294:innervation; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D009478:Neuropeptide Y / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D012018:Reflex / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology
chemical_list: D009478:Neuropeptide Y; D001030:Apamin; D009270:Naloxone; D004246:Dimethylphenylpiperazinium Iodide; D001285:Atropine; D002108:Ceruletide; D013806:Theophylline; D010646:Phentolamine; D006145:Guanethidine