Central Versus Peripheral Mechanism of Deglutitive Inhibition

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Deglutitive inhibition in the skeletal muscle esophagus can be explained based on the inhibition of neuronal discharges in the brain stem. On the other hand, a peripheral mechanism of deglutitive inhibition is also present. Studies show that similar to closely spaced swallows at short intervals, high-frequency electrical stimulation of the peripheral end of vagus nerve at short intervals, and intramural stimulation of the smooth muscle strips in vitro, induce period of inhibition during the stimulation and contraction following the last stimulus. Low-frequency successive stimulation of the vagus induces contraction with the first and last stimuli (A and B waves or “on” and “off” contractions). Same is observed in the muscle strip experiments. The occurrence of “on” and “off” contractions is explained on the basis of inhibition and muscle refractoriness. High-frequency stimulation induces strong initial inhibition and therefore a second stimulus, immediately following the first, inhibits contraction induced by the first stimulus. On the other hand, refractoriness of the muscle following first stimulus prevents contraction from the low-frequency second stimulus. There are gradients of refractory period and inhibitory innervations along the length of esophagus with stronger refractory period and inhibitory innervations in the proximal and distal esophagus, respectively [165].