Episodic prolactin and growth hormone secretion not related to the actual suckling activity in lactating rats

Nagy, Gyula; Kacsóh, B.; Halász, Béla

doi:10.1677/joe.0.1110137

Cited by 16 publications

(4 citation statements)

References 15 publications

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“…Prolactin levels were within the range reported for lactating animals and showed the characteristic dechne as a function of lac¬ tational age (Mattheij et al 1984). In agreement with previous results (Södersten & Eneroth 1984, Nagy et al 1986), we observed no exact concordance between peaks in PRL levels and suckling episodes. There were no significant differences between samphng intervals at any lactational age studied.…”

Section: Resultssupporting

confidence: 89%

Suppression of LH secretion in food-restricted lactating females: effects of ovariectomy and bromocryptine treatment

Cd¹,

Mitchell²,

Bc³

1995

Journal of Endocrinology

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It has been shown that restricting food in lactating rats for the first 2 weeks postpartum at a level of 60% of the ad-libitum daily ration increases the length of lactational dioestrus by about 7 days but little is known about correlated changes in hormone levels. In the first experiment we report changes in LH, prolactin (PRL) and ACTH secretion in food-restricted and ad-libitum fed lactating rats at various stages of lactation. Our results demonstrate that food restriction during the first 2 weeks of lactation did not affect PRL or ACTH secretion, but decreased plasma LH levels despite comparable GnRH receptor density between food-restricted and ad-libitum fed females. In the second experiments we investigated a possible causal relationship between the increased secretion of progesterone seen in food-restricted females and the suppression of plasma LH levels, by determining the effects of bromocryptine treatment and ovariectomy on LH secretion in both ad-libitum fed and food-restricted lactating females. LH suppression in food-restricted lactating females was not affected by ovariectomy or bromocryptine treatment, although the latter treatment significantly increased GnRH receptor number. These data suggest that factors other than ovarian steroids, PRL or increased adrenocortical activity modulate LH secretion and the length of lactational dioestrus in food-restricted lactating females.

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Section: Resultssupporting

confidence: 89%

Suppression of LH secretion in food-restricted lactating females: effects of ovariectomy and bromocryptine treatment

Cd¹,

Mitchell²,

Bc³

1995

Journal of Endocrinology

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“…In nonseparated lactating dams whose mammary glands are not engorged because of constant milking activity, only low serum PRL values are observed [9,10]. We carried out experiments both with dams that were not litter deprived and with dams separated from their pups during 4 and 16 h, and we found the highest serum PRL levels in mothers with 16-h separation.…”

Section: Tc # 230mentioning

confidence: 86%

“…However, higher serum PRL levels are not observed in dams that were never litter deprived [9,10], suggesting that other factors besides suckling are involved in enhanced suckling-induced serum PRL levels.…”

Section: Introductionmentioning

confidence: 92%

Suckling-Induced Serum Prolactin Levels Are Modified by Interference with Milk Ejection in Lactating Rats1

Voloschin

Gallardo

Tramezzani

1998

Biology of Reproduction

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The aim of this study was to determine whether suckling-induced prolactin (PRL) levels were modified when milk ejection was impaired. Milk ejection impairment was achieved in two experimental models: a) depriving the dam of sleep during suckling and b) increasing the nonsuckling intervals in lactating dams. Sleep deprivation blocked milk ejection and enhanced suckling-induced PRL levels in dams that had been previously separated from their pups. When milk ejection is blocked in litter-deprived dams, mammary glands are not evacuated and they remain engorged. Suckling stimuli were not the cause of the difference in suckling-induced serum PRL levels in control and sleep-deprived dams. The engorgement of the mammary glands may play a role, as a maximum suckling-induced PRL increase was not observed in nonseparated SD dams with nonengorged mammary glands. Moreover, suckling-induced PRL levels were decreased when engorged mammary glands of SD dams were evacuated through an oxytocin injection. A parallel increase between suckling-induced PRL levels and mammary gland weight was observed in the experiments in which milk ejection was impaired through an increase in the intervals of nonsuckling, providing additional support for a relationship between mammary gland engorgement and the regulation of suckling-induced PRL levels.

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“…2) [13] in NRS-injected rats. During the 2.5-hour test period, P R L was secreted in one or two bursts.…”

Section: Effect O F Vp-ab and N R S On The Episodic Release O F P R Lmentioning

confidence: 92%

Attenuation of the Suckling-Induced Prolactin Release and the High Afternoon Oscillations of Plasma Prolactin Secretion of Lactating Rats by Antiserum to Vasopressin

1991

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To investigate the role of vasopressin in prolactin (PRL) release during lactation, vasopressin antiserum (VP-Ab) was administered to lactating rats, giving it intravenously 15 min before permitting their previously isolated pups to suckle or to continuously suckled rats. The suckling-induced rise in plasma PRL levels was significantly less in VP-Ab-treated mothers than in rats receiving a similar amount of normal rabbit serum (NRS). The inhibitory effect of VP-Ab could not be detected on the next day. Angiotensin II antiserum (AII-Ab) had no effect on plasma PRL response induced by suckling. VP-Ab given to continuously suckled rats reduced the high amplitude oscillation of PRL concentration observed in NRS-injected rats. A transient increase of water intake was detected on the day of VP-Ab treatment only, which provides direct evidence for at least partial neutralization of vasopressin in the circulation. These findings suggest that vasopressin released from the neural lobe of the pituitary gland is essential for the normal PRL secretory response induced by suckling and the episodic pattern of PRL release in continuously suckled mother rats. Furthermore, these results support the assumption that disturbance in the regulation of water and electrolyte balance at the level of the neuro-intermediate lobe of the pituitary gland may alter PRL secretion during lactation.

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Episodic prolactin and growth hormone secretion not related to the actual suckling activity in lactating rats

Cited by 16 publications

References 15 publications

Suppression of LH secretion in food-restricted lactating females: effects of ovariectomy and bromocryptine treatment

Suppression of LH secretion in food-restricted lactating females: effects of ovariectomy and bromocryptine treatment

Suckling-Induced Serum Prolactin Levels Are Modified by Interference with Milk Ejection in Lactating Rats1

Attenuation of the Suckling-Induced Prolactin Release and the High Afternoon Oscillations of Plasma Prolactin Secretion of Lactating Rats by Antiserum to Vasopressin

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