Post-Caesarean Ovulation in the Rat

Abstract

Summary. Delivery by Caesarean Section (CS) of pregnant rats at 09.00 hours on the 23rd day of gestation reduced the range of times of ovulation after parturition by 18 hr. Ovulation had not occurred by 15 hr after CS but was completed by 18 hr, an interval which is similar to that of ovulation for females of this colony littering at 09.00 hours.

Reflexive Ovulation in the Rat, Induced by Caesarian Section, Is Blocked by Pelvic and/or Hypogastric Nerve Transection

“…Therefore, it is likely that afferent activity from the cervix via both the hypogastric and pelvic nerves mediates the full expression of this reflexive ovulation. Thus, in the case ofligature of the uterine horns, cervical stimulation by the fetuses was prevented and ovulation did not occur [11]. A contribu tion by uterine and/or vaginal afferent activity cannot be ruled out.…”

“…LH-antiserum successfully blocked ovu lation only when administered within 1 h postpartum [10]. Furthermore, Johnson [11] found that the time of day when the postpartum LH surge and subsequent ovu lation occurred covaried, on an individual basis, in close temporal relation to the time of day when the individual parturition occurred. The phase of the light cycle interacts with the time of parturition in determining the timing of postpartum ovulation [11,18].…”

“…Furthermore, Johnson [11] found that the time of day when the postpartum LH surge and subsequent ovu lation occurred covaried, on an individual basis, in close temporal relation to the time of day when the individual parturition occurred. The phase of the light cycle interacts with the time of parturition in determining the timing of postpartum ovulation [11,18]. These findings suggest that there exist both a reflexogenic and a circadian component to the control of postpartum ovulation.…”

“…As a test of the possible role of uterine afferent activity in stimulating postpartum ovulation, Johnson [11] per formed caesarian section (CS) at 9 a.m. on day 22 of preg nancy and observed that ovulation followed within 18 h. Ligature of the uterine horns at the time of CS blocked the induced ovulation [11], It seems likely that the ovula tion blockage was due to the uterine ligation's interrup tion of uterine afferent activity generated by the CS proce dure. Since uterine afferent activity is conveyed via the hypogastric and pelvic nerves [ 12,13], we hypothesized that transection of the hypogastric and/or pelvic nerves prior to CS (on day 22 of pregnancy) would interrupt the ovulation-inducing effect of CS.…”

Further studies of post-partum ovulation timing in mice

“…Since then, a number of investigators (e.g. Rebar, Nakane & Midgley, 1969;Johnson, 1972;Hashizume, Sugawara & Takeuchi, 1973;Ying, Gove, Fang & Greep, 1973; Morishige, Pepe & Rothchild, 1973) have more closely delineated the time of LH release and/or ovulation in rats after parturition. Similar studies, however, have not been pursued extensively in the mouse.…”