Effect of Noradrenaline and Isoprenaline on the Circular and Longitudinal Muscle of the Oestrogen Dominated Rabbit Uterus

Abstract

Longitudinal and circular muscle strips from the oestrogen dominated rabbit uterus were stimulated in vitro with the α‐ and β‐adrenergic stimulating drugs, noradrenaline and isoprenaline. The isometric contractions were recorded. Noradrenaline produced an increase in force and frequency of the contractions. No differences were found between the circular and the longitudinal muscle strips, or between the different parts of the uterus. Isoprenaline produced an inhibition of the spontaneous activity of the muscle strips. There was a difference between the response of the circular and the longitudinal muscle strips. The spontaneous activity of the longitudinal strips could be totally inhibited when isoprenaline was present in the organ bath in the concentration 2 × 10‐7M. The spontaneous activity of the circular strips could only be inhibited by approximately 50%, even with isoprenaline in a concentration of 2 × 10‐6M. Higher concentrations of isoprenaline had a stimulating effect. The ED50 of the circular strips was 60 times the ED50 of the longitudinal strips. No difference was found between the different parts of the uterus. No obvious alteration with regard to the sensitivity to the drugs was observed after cold storage for 24 hours.