Abstract

We have determined the effects of adrenergic activators and adrenergic blocking agents on isometric and isotonic contractions produced by segments of isolated rat uteri.

EPI, IS and PE all produce uterine inhibitory responses that are not modified by alpha adrenergit blocking agents, such as phentolamine, phenoxybenzamine, tolazoline and Dibozane. The uterine inhibitory responses to EPI, IS and PE are blocked by all compounds possessing some degree of beta receptor adrenergic blocking action. There were no qualitative differences in the drug responses determined in rat uterine segments in different phases of the estrus cycle, including those segments obtained from pseudopregnant and pregnant rats. There were no qualitative differences noted in the rat uterus that was primed with diethylstilbestrol or not primed. Finally, there were no differences noted when different strains of rats were used (Charles River, Wistar, Holtzman).

We have been able to demonstrate the presence of only beta inhibitory receptors in isolated rat uterine segments. We have been unable to detect the presence of either alpha excitatory or alpha inhibitory adrenergic receptors.