Hormonal changes around the parturition in rats.

Yoshida, Takeshi; Suzuki, Hiroshi; Hattori, Yutaka; Noda, Kiichiro

doi:10.1620/tjem.135.87

Cited by 12 publications

(5 citation statements)

References 9 publications

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“…The myoepithelium is undeveloped in pregnant animals (Radnor, 1972) with few oxytocin receptors (Soloff et ai, 1979;Soloff & Wieder, 1983), which could account for the difference in the size of contractions compared with lactating animals. In addition, it is possible that the high plasma concentrations of hormones such as relaxin (Sherwood, Crnekovic, Gordon & Rutherford, 1980), oestradiol, progesterone, cortisol and oxytocin (Yoshinaga, Hawkins & Stocker, 1969;Yoshida, Suzuki, Hattori & Noda, 1981) present in pregnant animals may inhibit the functioning of myoepithelium (Deiss, 1971; Summerlee, O'Byrne, Paisley, Breeze & Porter, 1984).…”

Section: Discussionmentioning

confidence: 99%

“…It can be concluded, therefore, that the interval between the first and second lactation periods was sufficient to prevent any increase in the efficiency of the second lactation compared with the first. However, in the 1-month period, the changes in the central and peripheral components of the reflex would have regressed, and the hormonal state of the animals would have become similar to virgin animals (Radnor, 1972;Yoshida et al, 1981;Theodosis & Poulain, 1984).…”

Section: Discussionmentioning

confidence: 99%

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Changing characteristics of the milk-ejection reflex during pregnancy, lactation and after weaning in the rat

Sutherland¹,

Aizlewood²,

Wakerley³

1986

Reproduction

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The pattern of reflex milk ejection during suckling was investigated in anaesthetized Wistar rats at various stages of pregnancy, lactation and after weaning. Milk-ejection responses were measured using intramammary pressure recordings, and the amount of oxytocin released was estimated from log dose-response lines compiled from the mammary responses to exogenous oxytocin. The number of rats showing intramammary pressure responses to oxytocin increased on Day 22 of pregnancy (the day of parturition) and decreased at 8 days after weaning. The dose-response lines from pregnant animals were shallow, but steepened and shifted to the left during lactation and after weaning. Reflex milk-ejection responses during suckling were detectable in primigravid animals, indicating that birth of the litter and previous suckling experience are unnecessary for the immediate functioning of the reflex. Reflex milk-ejection responses improved during early lactation (such that the frequency and the amount of oxytocin released at each response were maximal at Day 10 of lactation), and subsequently declined in late lactation. Although the frequency of responses in animals 2 and 4 days after weaning was similar to that in late lactating animals, the amount of oxytocin released at each response had risen again to mid-lactation values. In animals undergoing a second pregnancy and lactation the pattern of change in the milk-ejection responses was similar to that of primiparous animals.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Changing characteristics of the milk-ejection reflex during pregnancy, lactation and after weaning in the rat

Sutherland¹,

Aizlewood²,

Wakerley³

1986

Reproduction

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show abstract

“…On the other hand, it is less likely that A11 is involved in maintaining the low levels of prolactin seen on the days of metestrus and diestrus. During pregnancy and lactation, ovarian hormone levels are also changing, with particularly high levels around the time of parturition (21). Prolactin levels are elevated in late gestation and during lactation (22,23).…”

Section: Discussionmentioning

confidence: 99%

The Brain Renin‐Angiotensin System and the Regulation of Prolactin Secretion in Female Rats: Influence of Ovarian Hormones

Myers

Steele

1989

J Neuroendocrinology

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This study was designed to investigate the effects of exogenous and endogenous angiotensin II (All) on prolactin release in ovariectomized rats, with and without estrogen and progesterone pretreatment. In the first series of experiments, All or vehicle was injected into the third cerebral ventricle of conscious, freely-moving rats. In both treated and untreated rats, administration of 50 ng All suppressed prolactin levels within 15 min of injection, compared to vehicle-injected rats. In untreated rats, prolactin levels returned to baseline values by 30 min, while in treated rats, prolactin levels remained suppressed for an hour.In the second series of experiments, the involvement of endogenous brain All in tonically suppressing prolactin release was assessed by administering either All receptor blockers (saralasin or sarthran) or an All synthesis inhibitor (enalaprilat, an inhibitor of the conversion of angiotensin I to All). Neither All receptor blockade nor converting enzyme inhibition resulted in any change in prolactin levels in untreated levels in untreated rats. However, following treatment with ovarian steroids, infusion of saralasin or injection of enalaprilat resulted in a significant increase in plasma prolactin titers. During saralasin infusion, prolactin levels were significantly increased by 15 min and continued to be higher than controls at 60 min. After enalaprilat administration, prolactin levels did not rise significantly until 90 min and then remained elevated up to 120 min post-injection. These latter results suggest that at least one h is required for maximal inhibition of angiotensin synthesis in the brain.These data demonstrate that low doses of All suppressed basal prolactin secretion in both untreated and ovarian steroid-treated, ovariectomized rats. However, treated rats appeared to be more sensitive than untreated animals to the prolactin-lowering effects of centrally administered All. The lack of prolactin response in untreated rats when brain All synthesis was inhibited or All receptors were blocked suggests that, in the absence of ovarian steroids, endogenous All was not acting tonically to suppress prolactin secretion. Following exposure to ovarian steroids, however, the endogenous brain All system appeared to be activated and involved in controlling prolactin release.The anterior pituitary gland hormone, prolactin, i s involved in lactation, ovarian and mammillary gland function, pseudopregnancy in female rats, and i s released in response to stress (1). In human males and females, hyperprolactinemia i s associated with impaired sexual behavior and functioning, as well as infertility (2).Prolactin secretion is mainly under tonic inhibitory control by dopamine, derived from the brain tuberoinfundibular system (3). On the other hand, a variety o f peptides (e.g. vasoactive intestinal peptide, thyrotropin-releasing hormone) including angiotensin I1 (AII), have been identified as putative prolactin-releasing factors when applied directly to the anterior pituitary gland (4). Und...

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“…The similarity in the behavioral profile of PPE and cycling females may respond to similar changes in sexual steroids levels-estrogen peak followed by progesterone peak-that precede both behavioral estrus. Thus, Connors and Davis (1980) reported that estrogen plasma levels that increase during parturition [117] decrease after it (although Carrillo-Martínez et al, 2011, reported a slight augment at 9 h postpartum [115]), while progesterone levels peak at 9 to 12 h postpartum, coinciding with the period of maximal sexual activity [104]. In accordance, Sodersten and Eneroth (1981) found a close relationship between the preovulatory peak of progesterone and the onset of sexual receptivity in cycling females [118].…”

Section: Postpartum Estrus: a Unique Reproductive Period When Sexual ...mentioning

confidence: 94%

Adolescence and Postpartum: Two Life Periods to Deepen Our Understanding of the Complexity of Female Rat Sexual Behavior

Agrati

2022

Sexes

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The sexual behavior of the female rat has been extensively studied and used as a model for human female sexuality. The development of models that focus on sexual interaction from the female’s perspective has demonstrated the complexity of this behavior, in which motivational and affective aspects have great relevance. This review describes, from a historical perspective, some of the studies that have shed light on this complexity and presents the potential of two periods in the female’s life to expand our understanding of sexual behavior: adolescence and postpartum estrus. Cycling adolescent female rats can express sexual behavior even though some of the underlying circuitry is still developing. Therefore, this is an ideal time for studying the ontogeny of sexual behavior, the interaction of sexual and social motivations, and the neuroendocrine changes that lead to adult behavior. Female rats also show a fertile estrus a few hours after parturition. During this period, rats are simultaneously sexually and maternally motivated, making postpartum estrus an excellent model for exploring the interaction of these two social motivations. What we know so far about female sexual behavior in these unique periods of life reaffirms its richness and shows that much remains to be known.

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Hormonal changes around the parturition in rats.

Cited by 12 publications

References 9 publications

Changing characteristics of the milk-ejection reflex during pregnancy, lactation and after weaning in the rat

Changing characteristics of the milk-ejection reflex during pregnancy, lactation and after weaning in the rat

The Brain Renin‐Angiotensin System and the Regulation of Prolactin Secretion in Female Rats: Influence of Ovarian Hormones

Adolescence and Postpartum: Two Life Periods to Deepen Our Understanding of the Complexity of Female Rat Sexual Behavior

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