The Timing and Possible Mechanisms of Cervical Opening in the Oestrous Rat

Abstract

SUMMARYThe time that the retention of luminal fluid begins and its release from the uterus in pro-oestrous rats was determined precisely using a dye injection technique. Oestradiol was found to cause dye retention in ovariectomized rats when provided continuously from an implant of 5 mg. Injections of 0-5 ,ug/d x 4 were ineffective. Administration of progesterone to rats bearing implants of oestrogen interfered with the ability of the uterus to retain dye. Treatment with relaxin for 28 h prevented retention of dye in pro-oestrous rats whereas treatment at the time of dye injection was without effect. Mechanical stimulation of the cervix did not cause loss of injected dye. It is suggested that the mechanisms of opening of the cervix at coitus and at the end of oestrus may differ.

Relaxin as a New Hormone*

“…This was due to increased distensibility of the cervix rather than to increased reabsorption of the fluid by the uterus. The sphincter-like action of the cervix of the rat has been studied using a dye injection procedure (128). Uterine retention in ovariectomized rats was obtained by estrogen implants, and retention of dye was prevented by treatment with porcine relaxin for 28 h. Treatment with relaxin at the time of the injection of dye was not effective, showing that relaxin affects the physical properties of the cervix rather than affecting a rapid action to change the tone of the cervical muscle.…”