Endogenous norepinephrine release induced by tyramine modulates intestinal ion transport

Publisher Website
Google Scholar
Abstract
To study the effects of endogenous norepinephrine on intestinal ion transport, the actions of an indirect sympathomimetic agent, tyramine, were tested on electrolyte fluxes in the short-circuited rabbit ileum in vitro. Tyramine (10-5 M) alone had no effect on short-circuit current or Na transport but increased Cl absorption. Tyramine decreased the short-circuit current, stimulated both Na and Cl absorption and increased tissue conductance when its breakdown by endogenous monoamine oxidase enzymes was inhibited by pretreatment with pargyline (10-4 M). Pargyline alone had no effect on short-circuit current and NaCl transport. The effect of norepinephrine on NaCl transport was inhibited by the .alpha.-adrenergic receptor antagonist, phentolamine (10-7 M). This response was prevented when animals were chemically sympathectomized with 6-hydroxydopamine. Although sympathectomy decreased measurable tissue norepinephrine by 80%, it did not alter basal short-circuit current, Na and Cl absorption and the short-circuit current response to glucose-stimulated Na transport and to exogenous norepinephrine. A pool of norepinephrine in intestinal adrenergic neurons released by tyramine affects intestinal ion transport but does not alter basal ion transport. Data suggest close neuropharmacologic similarities between the adrenergic nervous system in the intestine and other organs.

This publication has 13 references indexed in Scilit: