Involvement of substance P neurons in contractions of canine small intestine produced by mesenteric nerve stimulation.
Pathways for contractions of in vivo canine small intestine produced by mesenteric nerve stimulation (MNS) were studied. In intact and chronically sympathectomized dogs, contractions of jejunal and ileal segments were largely reduced by intra-arterial infusion of capsaicin (10-100 microM, 0.07 ml/min), substance P (SP) antagonist, (D-Pro4, D-Trp7.9) SP (4-11) (100 microM, 0.14 ml/min), hexamethonium (100-1000 microM, 0.07 ml/min) or atropine (100 microM, 0.07 ml/min). In chronically vagotomized dogs, capsaicin, SP-antagonist or atropine significantly reduced MNS-induced contractions, but hexamethonium did not. In dogs in which the coeliac and superior mesenteric ganglia had previously been removed, MNS caused no response although intra-arterial injection of 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP, 0.1 mumol) caused marked contractions. It may therefore be suggested that extrinsic SP neurons probably originating in spinal ganglia and intrinsic SP neurons receiving input from vagal preganglionic cholinergic neurons are involved in the excitatory pathways to MNS-induced contractions and that activation of these neurons excites myenteric cholinergic neurons, thereby causing contractions of the small intestine.
Neya
T
T
Department of Physiology, Okayama University Medical School, Japan.
Mizutani
M
M
Nakayama
S
S
D000320:Adrenergic Fibers / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007421:Intestine, Small / Q000294:innervation* / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000294:innervation* / Q000502:physiology; D013373:Substance P / Q000037:antagonists & inhibitors / Q000502:physiology*; D013562:Sympathectomy; D014630:Vagus Nerve / Q000502:physiology
D006584:Hexamethonium Compounds; D013373:Substance P; D018738:Hexamethonium; D001285:Atropine