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 β2-agonistic and α1-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 × 10−6 mol/l. The α1-antagonist prazosin has an inhibiting action in the same concentration range (EC50 = 14.0 × 10−6 mol/l). To inhibit the contractile response to the same degree by the β2-agonist terbutaline the concentration has to be > 10−3 mol/l. From received results the β (β2)-adrenoceptor mediated effects seem to be of minor importance compared to the α (α1)-receptor dominance in the isthmus muscle during oesterus.