Stimulation of the peristaltic reflex by sodium chloride in guinea-pig isolated ileum

Abstract

Sodium chloride (64.1 mM-128.3 mM) added to Tyrode's solution bathing the serosal surface of guinea-pig isolated ileum, contracted the longitudinal muscle but had no effect on the peristaltic reflex elicited by raising the intraluminal pressure at constant time intervals of 10 min. However, the addition of sodium chloride in concentrations from 171.5–213.7 mM depressed and sometimes abolished the peristaltic reflex. With the higher concentrations of sodium chloride, slow and incomplete relaxation of the circular muscle occurred and in some experiments the contraction was so strong that it prevented intestinal filling. On the other hand. sodium chloride (42.7 mM–213.7 mM) added to ileum subjected to continuously raised intraluminal pressure contracted the longitudinal and the circular smooth muscles and transiently stimulated the peristaltic activity producing full, strong and regular peristaltic waves. Hyperosmotic solutions of added urea (up to 435 mM), saccharose (up to 350 mM) or Tris chloride (up to 174mM) had virtually no effect on the peristaltic reflex or on the activity of the guinea-pig ileum subjected to continuously raised intraluminal pressure. Sodium chloride antagonized the peristaltic block produced by hexamethonium, tetraethylam-monium, noradrenaline, adrenaline and 5-hydroxytryptamine. but not that caused by atropine, hyoscine, nicotine, dimethylphenylpiperazinium, calcium or magnesium. Sodium chloride may act by increasing the output of acetylcholine, but a direct and the facilitating effect of sodium chloride on the transmission of impulses in synapses of the peristaltic reflex or an action of the muscle cannot be excluded.