The effect of D2343 in transmurally stimulated rabbit isthmus muscle

In in vitro experiments spirally cut isthmic preparations from oestrogenized rabbits have been contracted by transmural stimulation. The beta 2-agonistic and alpha 1-antagonistic drug D2343 (for chemical structure, see fig. 1 in Olsson et al. 1984) inhibits the evoked contractions in a concentration related fashion with 50% effect at 9.6 X 10(-6) mol/l. The alpha 1-antagonist prazosin has an inhibiting action in the same concentration range (EC50 = 14.0 X 10(-6) mol/l). To inhibit the contractile response to the same degree by the beta 2-agonist terbutaline the concentration has to be greater than 10(-3) mol/l. From received results the beta (beta 2)-adrenoceptor mediated effects seem to be of minor importance compared to the alpha (alpha 1)-receptor dominance in the isthmus muscle during oestrus.