[Regulation of the anal canal pressure as revealed by myoelectrical activity of the internal anal sphincter].
Dogs were decerebrated under short-acting anesthesia and the intraluminal pressure within anal canal was continuously recorded through micro-balloon probe, simultaneously with myoelectrical activities of left and right internal anal sphincters. The rate of pressure 'ripples' was identical with that of 'slow spikes' recorded from the internal sphincters. When a transient drop in anal canal pressure was induced by rectal distension, observing the so-called 'recto-anal reflex', the 'ripples' in pressure and the 'slow spikes' of sphincters disappeared at once, and then, reappeared simultaneously in manometric and myoelectrical recordings at recovery phase of the reflex. It is concluded, therefore, that the 'slow spikes' of sphincters are directly coupled with mechanical responses of those muscles, and that the sustained contraction of internal sphincters maintains the pressure level and their temporary relaxation causes the pressure fall. The specific features of anal canal activity resulted by sacral denervation were seen on the chronic dogs kept alive over 20 days after nerve sections. The most remarkable ones were: prolonged inhibition of 'slow spikes' in the recto-anal reflex and marked formation of the reflex rebound. These findings indicate that not only inhibitory but also after-facilitatory processes in the reflex are potentiated in chronically denervated dogs. It is suggested that the myenteric neuronal circuit with lumbar sympathetic outflow have been re-organized under the condition of sacral denervation and those re-organized circuits are responsible for altered reflex pattern.
D000200:Action Potentials; D001003:Anal Canal / Q000502:physiology*; D000818:Animals; D003655:Decerebrate State; D004285:Dogs; D004558:Electric Stimulation; D008160:Lumbosacral Plexus / Q000502:physiology; D009119:Muscle Contraction; D009121:Muscle Denervation; D011312:Pressure; D012018:Reflex