Studies on the spasmolytic and uterine relaxant actions of n -ethyl and n -benzyl-1,2-diphenyl ethanolamines: elucidation of the mechanisms of action

Abstract

The influence of N -ethyl- and N -benzyl-1,2-diphenyl ethanolamines (compounds E and B, respectively) was examined on the spontaneously contracting rabbit jejunum and the rat uterus together with their influence on the contractions induced by some spasmogens in the guinea-pig ileum and oxytocics and CaCl2in the pregnant rat uterus. Both E and B inhibited the spontaneous contractions of the rabbit jejunum with ID50values of 0.13 and 0.03 micromol ml-1. Their inhibitory activities were not antagonized by alpha- or beta-adrenoceptor blockers but significantly reversed by CaCl2(0.015 micromol ml-1). The compounds also antagonized nicotine, ACh-, histamine-, 5-HT- and CaCl2-induced contractions by 44-100%. Compound E seemed to be several times more potent than B in inhibiting the spontaneous uterine contractions with an ID50of (7 nmol ml-1). Their inhibitory effects were not antagonized by beta2-adrenoceptor or H2-receptor blocking drugs. Both compounds (40 nmol ml-1) antagonized in a competitive manner CaCl2-induced contractions in the K+-depolarised uterus and PGE2and oxytocin-induced uterine contractions. The ID50values were in the range of 1.6-10.7 nmol ml-1. The results suggest that E and B compounds may be considered as putative L-Ca2+channel blockers with certain selectivities. The E compound seemed to be more selective against uterine L-Ca2+channels and the B compound against intestinal smooth muscles. Thus, the compounds may be of potential value in treatment of some colics, the irritant bowel syndrome, dysmenorrhoea and premature deliveries.