S. Plas-Roser

Stress related effects in the control of sexual receptivity and in the secretion of progesterone by the adrenals in cyclic female rats

Abstract The present study examined the acute effects of ether anaesthesia and/or blood removal by heart puncture on progesterone blood concentration at different times of proestrus and on subsequent estrous mating behavior during the night following proestrus in sham adrenalectomized and adrenalectomized 4-day cyclic female rats. A statistically significant increase in blood progesterone concentration was observed on proestrus at 09:00, 13:30 and 15:30, a very short time after heart puncture under a 3 min ether anaesthesia in sham adrenalectomized rats as compared to their adrenalectomized counterparts. Following this blood removal procedure at the preceding times a greater number of sham adrenalectomized female rats displayed mating behavior (17/20) than their adrenalectomized counterparts (11/23). It is suggested that adrenocortical related effects of ether anaesthesia and/or surgical manipulations may be involved in the display of estrous sexual receptivity in the rat.

Does corpus luteum function autonomously during estrous cycle in the rat? A possible involvement of LH and prolactin

This study examined the of LH and prolactin in the control of corpus luteum function during 4-day cycles in the rat. Bromocriptine (BRC) treatment was performed on proestrus or/and estrus morning that means before or after the preovulatory release of LH. This caused complete blood prolactin depression from the time of injection until diestrus 1 afternoon. This decrease in blood prolactin concentration was associated with a rise in the tonic level of LH secretion in those females which received BRC as soon as on proestrus. We first observed that injection on the morning of proestrus of doses of BRC capable of blunting prolactin secretion on proestrus afternoon did not significantly impair the preovulatory release of LH and did not prevent ovulation occurring during the following night. The life span of the corpora lutea edified from ovarian follicles rupturing before or under BRC administration did not exceed that of those formed under physiological circumstances since 4-day cycles culminating in ovulation constantly took place in all the treated animals whatever the time of BRC injection. To determine the pattern of luteal activity in the absence of prolactin secretion, we measured blood progesterone concentration from estrus until late diestrus in female rats injected with BRC on proestrus and/or estrus at 1100 h. The initiation of the function of corpus luteum on estrus and the achievement of its full activity on diestrus 1 did not appear to be affected by BRC. By contrast the level of blood progesterone declined more rapidly on the morning of diestrus 2 in BRC-treated than in control females. The capacity for autonomous progesterone secretion by corpus luteum of the cycle was discussed in the light of previous and present observations.

Progesterone secretion by luteinized unruptured follicles in mature female rats

The ability of luteinized unruptured follicles (LUF) to display luteal activity was investigated in mature female rats. Previous findings in our laboratory showed that increasing doses of LH, when injected on late diestrus in 4-day cyclic rats, were capable of inducing the formation of either LUF or postovulatory corpora lutea (POCL) in a dose dependent manner. Four-day cyclers were injected on diestrus 2 at 4.30 p.m. (day 0) with 2.7 micrograms or 5.4 micrograms/100 g of an ovine LH preparation (x 2.94 NIH LH S3) and were killed at different times during the three successive days following injection. Natural 4-day cyclers were killed at corresponding times following spontaneous LH release on proestrus afternoon (day 0). Both LUF and POCL were observed in LH-treated females. LUF appeared more numerous in females given 2.7 micrograms LH than in both natural cyclers and in females injected with 5.4 micrograms LH. On day 1 during the rising phase of luteal activity serum progesterone (P) level did not differ in the three groups despite the high number of LUF in females given 2.7 micrograms LH. On day 2 at 11 a.m. lower P values were observed in both groups of LH-treated females than in natural cyclers, this corresponding to a greater proportion of LUF in the former than in the latter. On day 2, at 5 p.m. by the time of full activity of POCL in natural cyclers, P did not differ in the three groups irrespective of the relative number of ruptured or unruptured follicles. On day 3, P sharply declined in LH-treated and natural cyclers. These results suggest that LUF are capable of secreting P during a period corresponding to the duration of corpus luteums life span in cyclic female rats.

Do luteinized unruptured follicles secrete progesterone in mature female rats.

Unruptured luteinized follicles were shown to secrete less progesterone than did postovulatory corpora lutea in cyclic female rats.

How different procedures of blood removal affect blood progesterone concentration in the cyclic female rat

The effects of different procedures of blood removal on blood progesterone level were studied in female rats throughout the diestrous period of estrous cycle. Unoperated, sham operated, adrenalectomized and ovariectomized females were used. The complete manipulation comprising ether anaesthesia and blood collection lasted 3-4 min. Blood removal in itself did not exceed one minute. Blood progesterone levels appeared to be higher in unoperated, sham operated and ovariectomized females bled by heart puncture or from the abdominal vena cava under ether anaesthesia than in their decapitated counterparts bled without ether anaesthesia. Adrenalectomy prevented this effect from occurring. No difference in blood progesterone concentration was noted between anaesthetized and unanesthetized decapitated unoperated females. It was concluded that some procedures of blood removal under ether anaesthesia might cause a stress-related rise in blood progesterone concentration and that ether anaesthesia was not involved.

Evidence that a critical period exists for LH release during diestrus in the cyclic female rat

Abstract The aim of this work was to determine whether the neurogenic mechanisms which trigger LH release during the critical period in the afternoon of proestrus could be revealed during the diestrous period of the cycle.

Does prolactin control the blood progesterone level on early dioestrus in rats

Bromocriptine treatment on either prooestrus or oestrus in female rats did not affect luteal function on the day of dioestrus 1.