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

Abstract

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.

A Neuro-hormonal Circuit for Paternal Behavior Controlled by a Hypothalamic Network Oscillation

“…and collected tail blood 30 min post-administration to determine serum Prl and brain tissue to assess pSTAT5 immunofluorescence ( Figure 6 A). Administration of Prl raised serum Prl levels from 0.61 ± 0.04 × 10 −3 mg/kg to 100.60 ± 10.96 × 10 −3 mg/kg ( Figure 6 D), a serum concentration typically found in rat and mouse lactating dams ( Voloschin et al., 1998 ; Guillou et al., 2015 ), and induced an increase in pSTAT5 immunofluorescent cells from 26.63 ± 2.70 to 381.90 ± 25.38 MPOA cells per section ( Figures 6 B and 6C). Last, to trigger endogenously sourced hypersecretion of Prl, virgin male rats received an i.p.…”

“…We addressed this issue by using optogenetic stimulation to impose a range of electrical frequencies on TIDA neurons and recorded the resultant dopamine concentrations at the release site in the median eminence (ME) by fast-scan cyclic voltammetry (FSCV; Figure 2 A). Stimulation of axon terminals rather than cell somata was performed because of concerns that the axonal connection may be lost during preparation of the mediobasal hypothalamus slice due to the complex three-dimensional nature of the dmArc and its projections ( Voloschin et al., 1998 ). Dopamine Transporter (DAT)-Cre mice were injected with Cre-dependent channelrhodopsin (ChR2) in the dmArc ( Figure 2 B), and frequencies spanning 0.1–0.8 Hz were applied.…”

“…The role of Prl, the downstream target of TIDA activity, is poorly understood in males, in particular how it pertains to behavior and parenting. Curiously, mating experience allows the behavioral transition from infanticide to paternal behavior, although only in biparental species ( McCarthy and Vom Saal, 1986 ; Voloschin et al., 1998 ). Thus, filling this gap in knowledge requires not only identifying the effect of Prl on male action patterns but also determining under which conditions Prl may affect male behavior toward offspring: is it necessary, sufficient, and/or permissive?…”

Complete sleep and local field potential analysis regarding estrus cycle, pregnancy, postpartum and post-weaning periods and homeostatic sleep regulation in female rats

“…On the level of delta activity, moderate rebound was seen between the 5th and 10 h hours of the LP (Fig. 8C), but delta power remained below the baseline level in the following period (hours [11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”

Negative correlation between milk production and brown adipose tissue gene expression in lactating mice

“…In many studies, lactating females have been separated from their pups before blood sampling to standardize their levels of circulating prolactin (e.g. Voloschin et al, 1998;Callahan et al, 2000). In our study, the females were kept with the pups to preserve putative inhibitory effects of suckling on thermogenesis in BAT.…”