Gap junctions in the myometrium of pelvic-neurectomized rats with blocked parturition.

Abstract

AbstractPregnant Sprague‐Dawley rats were laparotomized on days 8–10 and sham‐operated (S) or subjected to bilateral section of the pelvic parasympathetic nerves (pelvic neurectomy (PN)). Both S and PN animals were allowed to go to term and the time of delivery was recorded. Eight of ten S animals delivered on the afternoon of day 22 and two delivered on the morning of day 23. Pelvic neurectomy blocked parturition in five rats autopsied on day 24, and five rats autopsied on day 26. On these days the PN animals had full‐term fetuses; live on day 24, but dead on day 26. In a second study, the fine structure of the myometrium of S and PN pregnant rats was examined during the parturient period for the presence of gap junctions. Gap junctions were present between myometrial smooth muscle cells of the S group during delivery and in the PN group on days 23, 24, and 25, in the absence of delivery. There was a significant increase (p < 0.05) in the number of gap junctions on day 23 in the PN animals. There was no difference in the length of gap junctions in the different groups. These observations indicate that the parturition block characteristic of PN animals is not attributable to the failure of gap junction formation between smooth muscle cells. Apparently, the nervi erigentes participate in the orchestration of events terminating in parturition, but their specific role remains an enigma.