Neural inhibition of gastrointestinal smooth muscle motility in guinea-pigs.
The neural inhibition of the gastrointestinal (GI) smooth muscle motility was studied by means of electrical transmural nerve stimulation (ETNS) in guinea-pigs. In untreated muscle strips, ETNS induced four types of response, consisting of three basic components, i.e., contraction and relaxation during ETNS, and after-contraction. Following atropinization, all the responses changed to only one type, i.e., relaxation during ETNS followed by after-contraction. The relaxation of the muscle strips induced by ETNS after atropinization was not significantly reduced under superimposing guanethidine treatment in any site of the GI tract. The maximal relaxation of the muscle strips induced by ETNS after atropine and guanethidine treatments was not uniform throughout the GI tract. The relaxation of the gastric body and colon was greater than that of the jejunum and ileum. The extent of the relaxation was significantly different even in the colon. Theophylline and phentolamine did not reduce the ETNS-induced relaxation following atropine and guanethidine treatments in the distal colon and taenia coli. The findings suggest the following: the non-adrenergic inhibitory (NAI) nerve is the main postganglionic nerve to inhibit the GI smooth muscle motility; and the role of adrenergic nerve is of little importance in respect to postganglionic inhibition. The innervation of the NAI nerve seems not to be uniform throughout the GI tract. Theophylline and phentolamine are not the specific antagonists of the NAI nerve.
First Department of Medicine, Hamamatsu University School of Medicine, Japan.
M
M
Nawano
E
E
Kaneko
N
N
Honda
D000320:Adrenergic Fibers / Q000502:physiology; D000818:Animals; D002799:Cholinergic Fibers / Q000502:physiology; D004064:Digestive System / Q000187:drug effects / Q000294:innervation; D004068:Digestive System Physiological Phenomena; D004558:Electric Stimulation; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects; D010646:Phentolamine / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology
D013806:Theophylline; D010646:Phentolamine