Duration of Diestrous Period and Secretion of Progestins during Prolonged Lactation in the Rat

Tomogane, Hiroshi; Ota, Kei; Yokoyama, Akihiro

doi:10.1507/endocrj1954.23.137

Cited by 8 publications

(5 citation statements)

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“…Implantation of dormant blastocysts of litters of 9 or more suckling offspring around days 18-22 postpartum may occur in re sponse to desensitization (adaptation) of the hypothalamo-pituitary-ovarian system to ward suckling stimuli [Tomogane et al, 1976] and/or to decreasing stimuli of suck ling (i.e., the pups start to eat). As described by Yoshinaga [1961], as soon as the central stimulation by suckling is less intensive, pro lactin secretion decreases and increasing re lease of FSH-LH enhances estrogen and pro gesterone production by the ovarian corpora lutea.…”

Section: Discussionmentioning

confidence: 99%

Suckling-Induced Delay of Implantation and Increased Fecundity in Rats

Vorherr¹,

Vorherr²

1984

Gynecol Obstet Invest

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In rats fertilized during the 1 st or 2nd day postpartum (second consecutive pregnancy), suckling induces intrauterine blastocyst dormancy and delays implantation for 8–22 days. In spite of this relatively long time of blastocyst dormancy, associated with greatly reduced cellular metabolism, subsequent implantation and growth results in significantly larger litters (13.6 ± 0.62; x ± SE) than in primigravidas (10.4 ± 0.89) or in rats with a second-spaced pregnancy (11.2 ± 0.72). Enhanced fecundity in rats with second consecutive pregnancies may be attributed to increased ovarian blood supply of preceding gestation and/or to augmented pituitary FSH-LH secretion resulting in intensified ovarian gonadotropic stimulation for postpartum ovulation.

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Section: Discussionmentioning

confidence: 99%

Suckling-Induced Delay of Implantation and Increased Fecundity in Rats

Vorherr¹,

Vorherr²

1984

Gynecol Obstet Invest

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“…It was not possible, however, to advance the onset of maternal odor emission by allowing mothers to nurse PND 10 pups starting on day 1 postpartum, but the introduction of weanlings stopped odor emission by mother rats (Holinka and Carlson, 1976), presumably by stopping lactation, thereby decreasing maternal food intake (Ota and Yokoyama, 1967b). Continuing to maintain mothers with PND 14-21 pups maintains lactation (Selye and McKeown, 1934) and high levels of food intake (Tomogane, Ota, and Yokoyama, 1976) and allows mothers to continue emission of their attractive odor (Holinka and Carlson, 1976;Moltz, Leidahl, and Rowland, 1974).…”

Section: Pup Stimuli Control Maternal Odor Emissionmentioning

confidence: 99%

Neuroethology of olfactory preference development

Leon

1992

J. Neurobiol.

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Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training.

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“…We reported in the previous paper (Tomogane et al, 1976) that the concentration of progesterone in the ovarian vein blood of the mother rats was lower during prolonged lactation than during normal lactation.…”

Section: Insufficiencyofmentioning

confidence: 78%

“…In a previous paper, we reported changes in the ovarian function in lactating rats in which lactation was prolonged for a maximum of 60 days by replacing suckling pups periodically (Tomogane et al, 1976). Throughout the entire period of lactation we also recorded vaginal smears, body weight of the mother, gain in litter weight and weights of various endocrine organs at autopsy.…”

Section: Synopsismentioning

confidence: 99%

“…Definite decreases in weights of the anterior pituitary and the adrenal glands were observed.The food intake remained constant from day 15 of lactation onwards, therefore, the feed efficiency for milk production declined gradually during the period of normal lactation remaining at a low level thereafter.After the first recurrence of vaginal estrus which also occurred between day 20 and 30, the replacement of litters was followed by the appearance of estrus, whereas replacement before day 15 did not affect the ovarian function.In addition to these changes, a depressing effect of estrus on the milk production was observed.In a previous paper, we reported changes in the ovarian function in lactating rats in which lactation was prolonged for a maximum of 60 days by replacing suckling pups periodically (Tomogane et al, 1976). Throughout the entire period of lactation we also recorded vaginal smears, body weight of the mother, gain in litter weight and weights of various endocrine organs at autopsy.…”

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Changes in Body Weight, Milk Production, Food and Water Consumptions and Vaginal Smears in Rats during Prolonged Lactation

et al. 1976

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SynopsisConcurrent observations were made in the rat on the changes in the milk production, body and organ weight, food and water consumptions and in the ovarian function in two separate series of experiments in which the period of lactation was prolonged to 60 and 45 days, respectively, by replacing suckling pups by younger ones.In most of the variables examined, marked changes occurred between day 20 and 30 of lactation, that is, at the stage corresponding to the end of the normal lactation period.Milk production rate during prolonged lactation expressed by daily gain in weight of litters decreased to 60% of the level before day 20, and was associated with a great reduction of nucleic acid contents of the mammary gland. Definite decreases in weights of the anterior pituitary and the adrenal glands were observed.The food intake remained constant from day 15 of lactation onwards, therefore, the feed efficiency for milk production declined gradually during the period of normal lactation remaining at a low level thereafter.After the first recurrence of vaginal estrus which also occurred between day 20 and 30, the replacement of litters was followed by the appearance of estrus, whereas replacement before day 15 did not affect the ovarian function.In addition to these changes, a depressing effect of estrus on the milk production was observed.In a previous paper, we reported changes in the ovarian function in lactating rats in which lactation was prolonged for a maximum of 60 days by replacing suckling pups periodically (Tomogane et al., 1976). Throughout the entire period of lactation we also recorded vaginal smears, body weight of the mother, gain in litter weight and weights of various endocrine organs at autopsy.To obtain more information about prolonged lactation, we performed recently another series of experiment in which effects of the suckling stimulus on the secretion of prolactin and corticoids were investigated in prolonged lactating rats. In this series, body and organ weights of the mother, daily gain in litter weight and. vaginal smears were also recorded throughout 45 days of prolonged lactation. Food and water comsumptions of the mother, in addition, were measured daily in some animals of this series. The results obtained in two series were in good agreement, and, therefore, we are combining them.Part of the results of the hormonal secretion obtained in the second series has been reported as a short communication (Ota et al., 1974).Received for publication December 8, 1975.

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Duration of Diestrous Period and Secretion of Progestins during Prolonged Lactation in the Rat

Cited by 8 publications

References 11 publications

Suckling-Induced Delay of Implantation and Increased Fecundity in Rats

Suckling-Induced Delay of Implantation and Increased Fecundity in Rats

Neuroethology of olfactory preference development

Changes in Body Weight, Milk Production, Food and Water Consumptions and Vaginal Smears in Rats during Prolonged Lactation

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