Changes in Cholinergic and Noradrenergic Nerves in the Pregnant and Postpartum Uterus of the Albino Rat and Guinea Pig

Abstract

The present study was undertaken to investigate the structural changes in both cholinesterase(ChE)-positive nerve fibers and adrenergic nerves with formaldehyde-induced fluorescence in pregnant and postpartum uteri of both the albino rat and guinea pig. Particular attention was directed to the relationship between these changes and the local factors associated with the growing fetus. ChE reaction was absent in the control and pregnant uterus of the guinea pig. In the albino rat, there were signs of degeneration in pregnancy. These were evidenced by vacuolation of large nerve trunks and the presence of focal segments with very faint reaction along the course of the nerve bundles. Myometrial segments from fetus-containing horns showed some fragmented nerve fibers, but at the same time some other normal ones. Most of the fine nerve bundles gave a weak reaction. Three weeks after delivery, multiple ChE fibers were found in the uterus of the albino rat. The normal appearance was, however, not regained and some nerve fibers were still fragmented. Noradrenergic (NA) nerve fibers were disintegrated and markedly reduced in number in the myometrium of the pregnant uterus of both the guinea pig and albino rat, particularly in the uterine horns that were distended by fetuses. The number of NA fibers was not significantly reduced in the tubal ends of the albino rat uterus. Three weeks after delivery, normal NA fibers were seen in the myometrium of both the albino rat and guinea pig uterus. Nerves with reduced fluorescence reaction were observed less frequently.

Pregnancy-induced uterine neuronal degeneration in the rat

“…These results are consistent with previously reported findings of a decrease in both adrenergic and cholinergic fibers in the pregnant rat uterus (Hervonen et al 1973;Garfield 1986;Moustafa 1988;Kyozuka et al 1988;Yamada 1988). Most of the rare nerve bundles found in the body of the uterus at term were close to vessels, were approximately 5 µm in diameter, and were far less tortuous than corresponding bundles in the virgin (compare the morphology of "Intra 5" bundles in Figs.…”

“…These fragments were interpreted by Moustafa (1988) as remnants of degenerating nerve bundles. We were unable to trace these fragments in sufficient detail to confirm this interpretation, however.…”

“…Many anatomical (Garfield 1986) and physiological (Sato et al 1989) experiments have focused on this innervation in virgin rats. During pregnancy, however, the uterus of most mammals undergoes a profound denervation (Marshall 1981), a functionally important process that has been thoroughly described in the guinea pig (Owman 1981), but has not been thoroughly examined in the rat (Hervonen et al 1973;Moustafa 1988;Yamada 1988). We studied virgin, full-term (22-day gestation) and early postpartum (<48 h after delivery) rats to document the degeneration and regrowth of the uterine innervation.…”

Noradrenergic and Cholinergic Nerves in the Uterus of the Japanese Long-Fingered Bat, Miniopterus schreibersii fuliginosus, Change with Reproductive Cycle

“…Thus, there is a clear correlation between the degeneration of uterine NA and AChE nerves and rise of luteal activity in late period of pregnancy after hibernation. This suggests that progesterone acts as the major factor for pregnancyinduced nerve reduction in the bat as has been reported for the rat (Moustafa, 1988;Hasse et al ., 1997), guinea pig (Moustafa, 1988) andsheep (Reneger andRexroad, 1990). Reduction of NA and AChE nerves from the bat uterus in late pregnancy, as has been suggested in the rat (Moustafa, 1988;Hasse et al ., 1997), guinea pig (Moustafa, 1988) and sheep (Reneger and Rexroad, 1990), may be closely related to a regressive reorganization of neuronal influence that is relevant to the formation of placental circulation, and to quiescence of uterine contractility during pregnancy.…”

“…It has been well established that the uteri of mammals are innervated by sympathetic noradrenergic (NA) (Papka et al ., 1985;Moustafa, 1988;Renegar and Rexroad, 1990;Zoubina et al ., 1998) and parasympathetic acetylcholinesterase positive (AChE) (Moscarini et al ., 1982;Papka et al ., 1985;Moustafa, 1988;Renegar and Rexroad, 1990) nerves. The distribution and density of these two types of nerves differ among mammalian species.…”