THE CONTRIBUTION OF PROSTAGLANDINS IN THE MUSCLE OF HUMAN ISOLATED SMALL INTESTINE TO NEUROGENIC RESPONSES

Abstract

1 In strips cut parallel to the longitudinal or circular muscle, indomethacin (2-10 μg/ml) usually lowered the tone, thus probably accounting for the reduction of nerve-mediated relaxations to electrical field stimulation. 2 In longitudinal muscle strips, indomethacin enhanced contractions which occurred during electrical stimulation, probably because tone fell, but antagonized after-contractions. By contrast, in the circular muscle indomethacin reduced initial contractions but enhanced after-contractions. 3 Prostaglandin E₂ counteracted all of the effects of indomethacin in the longitudinal muscle and most of those in the circular muscle; prostaglandin F_2α restored circular muscle tone. 4 The results suggest that prostaglandins affect the muscle directly and contribute to the regulation of tone. They may also mediate non-cholinergic contraction in longitudinal muscle and suppress contractility in the circular muscle.