The absence of sensitivity changes of the rabbit oviduct to phenylephrine and isoproterenol during early gestation.

: The response of the rabbit perfused oviduct in vivo to phenylephrine (PE), isoproterenol (ISO) and epinephrine (EPI) was studied to determine if a purported change from alpha-adrenergic receptor dominance to beta-adrenergic receptor dominance during early gestation occurs (i.e. prior to implantation). The response of the tissue to PE did not change during early gestation, even in the presence of beta-receptor blockade by propranolol. The response to ISO of the PE-stimulated oviduct also did not change. However, the dose-response curve to EPI was shifted horizontally to the right 4 days after mating suggesting a tissue desensitization. It was concluded that the decreased oviductal sensitivity to EPI observed during early gestation could not be attributed to a change from alpha-receptor dominance to beta-receptor dominance.