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      Effect of Adrenalectomy on Mating-Induced Prolactin Surges and Pseudopregnancy in the Female Rat

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          In the estrous female rat, mating stimulation induces an acute surge of prolactin (PRL) within 20 min after mating followed by the onset of twice-daily PRL surges which persist for an 8- to 13-day period of acyclicity called pseudopregnancy. In Experiment 1, we examined whether the release of adrenal hormones after mating modulates mating-induced PRL secretion during the first 38 h after mating. Ovariectomized females were adrenalectomized (Adx) or sham-operated (Sham) and were implanted with jugular vein catheters 2 days later. They were given estrogen and progesterone and mated 6 days after the last surgery until they received 15 intromissions or 15 mounts-without-intromission from a male. Blood samples were collected beginning 20 min before mating at 23:00 h and continuing for 38 h. Plasma PRL concentrations were measured using radioimmunoassay. Mating that included intromissions induced an acute (20-min) PRL response which was higher in Adx than in Sham animals, and advanced in the Adx animals in the onset of the first daily PRL surge to 10:00 h, some 18 h before the surge was observed at 04:00 h in the Sham-mated animals. A small but measurable nocturnal surge was observed in Adx and Sham groups 18–24 h later at 04:00–10:00 h. In Experiment 2, Adx- and Sham-cycling animals received 5 (5I) or 7 (7I) intromissions from a male 12–16 days after surgery. Adx animals receiving 5I showed a significantly higher incidence of pregnancy or pseudopregnancy (%P/PSP) than did Sham 5I animals, while there was no difference in %P/PSP in the 7I groups. We conclude that adrenal gland secretions normally suppress plasma PRL concentrations immediately post-mating and before the onset of the nocturnal mating-induced PRL surge and also inhibit pseudopregnancy when females receive a subthreshold number of intromissions normally required for its induction.

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          Most cited references 14

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          Paced copulation in rats: effects of intromission frequency and duration on luteal activation and estrus length.

          When estrous female rats regulate or pace (P) the timing of vaginal intromissions received from males during mating, the stimulation is more effective in inducing luteal function and abbreviating the period of receptivity than is nonpaced (NP) stimulation. The present studies examined whether the coital stimuli necessary for each of these functional consequences are similar. In Experiment 1, estrous females received either 5 or 10 intromissions from males in P or NP tests; control animals received mounts-without-intromission (MO). The duration of estrus was not affected by 5P, 5NP, or 10NP stimulation, but was significantly abbreviated in 10P animals. In contrast, activation of prolonged luteal function occurred in 70% of 5P females compared to only 10% of 5NP females; luteal activation was similar in 10P and 10NP females (74% for both groups combined). In Experiment 2, male copulatory behaviors were compared in tests with P and NP females. Males tested with P females exhibited significantly longer intromission durations (616 +/- 21 msec) than did males tested with NP females (527 +/- 30 msec). Other measures of male copulatory performance such as the number of intromissions to ejaculation and the ejaculation latency did not differ between groups. These studies demonstrate that luteal activation is more readily induced by paced coital stimulation than is abbreviation of estrus. In addition, they suggest that differences between P and NP females in the behavioral and neuroendocrine responses to coital stimulation may result from differences in intromission duration displayed by males under these test conditions.
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            The physiology and mechanisms of the stress-induced changes in prolactin secretion in the rat

             Richard Gala (1990)
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              Prolactin release after mating and genitosensory stimulation in females


                Author and article information

                S. Karger AG
                September 2003
                02 October 2003
                : 78
                : 3
                : 138-146
                Department of Biology, Boston University, Boston, Mass., USA
                72795 Neuroendocrinology 2003;78:138–146
                © 2003 S. Karger AG, Basel

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                Page count
                Figures: 4, Tables: 2, References: 42, Pages: 9
                Reproductive Neuroendocrinology


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