Lactation deficit in OFA hr/hr rats may be caused by differential sensitivity to stress compared with Wistar and Sprague Dawley rats.

OFA hr/hr (OFA) rats present a major lactation deficit that impairs offspring survival. To explore whether abnormal stress responsiveness causes this deficit, we compared their hormonal (prolactin, progesterone, and corticosterone) responses to stress (room change and 2-min ether exposure) with those of Wistar and Sprague Dawley (SD) rats. We tested responses during the estrous cycle, pregnancy, lactation, after ovariectomy, and ovarian steroid hormone priming, and responses to suckling.

Effect of 2,4-dichlorophenoxyacetic acid on milk transfer to the litter and prolactin release in lactating rats.

The effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on brain monoamines and the serum level of hormones involved in milk synthesis and on the milk ejection reflex in rats were evaluated. Dams were treated with 2.5, 5, 15, 25, 50 or 70mg 2,4-D/kg bw according to two experimental designs: (a) through food from post partum day 1 (PPD 1) to PPD 16 and the respective control groups or (b) an unique i.

Effect of 2,4-dichlorophenoxyacetic acid on rat maternal behavior.

Exposure to 2,4-dichlorophenoxyacetic acid (2,4-D) has several deleterious effects on the nervous system such as alterations in the concentrations of neurotransmitters in the brain and/or behavioral changes, myelination rate, ganglioside pattern [Bortolozzi, A., Duffard, R., Antonelli, M.

Effects of methanolic extract of Asparagus pubescens root on sexual behavior and pituitary hormone secretion on Wistar rats during pregnancy and lactation.

We investigated the effect of methanolic extract of Asparagus pubescens root on sexual behavior and on pituitary hormone secretion during pregnancy and lactation on Wistar rats. Different doses (0.25, 0.

Hormonal profile and reproductive performance in lactation deficient (OFA hr/hr) and normal (Sprague-Dawley) female rats.

Lactation deficiency may have important consequences on infant health, particularly in populations of low socioeconomic status. The OFA hr/hr (OFA) strain of rats, derived from Sprague-Dawley (SD) rats, has deficient lactation and is a good model of lactation failure. We examined the reproductive performance and hormonal profiles in OFA and SD strains to determine the cause(s) of the lactation failure of the OFA strain.

Dopaminergic mechanisms involved in prolactin release after mifepristone and naloxone treatment during late pregnancy in the rat.

Background/aims: During late pregnancy, the antiprogesterone mifepristone facilitates prolactin release. This effect is enhanced by administration of the opioid antagonist naloxone, suggesting an inhibitory-neuromodulatory role of the opioid system. Since hypothalamic dopamine (DA) is the main regulator of prolactin release, in this study we explored the role of DA on prolactin release induced by mifepristone and naloxone treatment.

Neurotransmitters involved in the opioid regulation of prolactin secretion at the end of pregnancy in rats.

Using a pharmacological approach, we explored potential mechanisms for the regulation of prolactin secretion by opioid peptides at the end of pregnancy in rats. On day 19 of pregnancy, intracereboventricular administration of the mu-opioid receptor agonist (D-Ala2, NMe-Phe4, Gly-ol5)-enkephalin (DAMGO) or beta-endorphin (beta-END) induced a dose-related increase in serum prolactin levels 30 min later. Pretreatment with the opioid antagonist naloxone abolished the increase induced by DAMGO injection.

Luteal 3beta-hydroxysteroid dehydrogenase and 20alpha-hydroxysteroid dehydrogenase activities in the rat corpus luteum of pseudopregnancy: effect of the deciduoma reaction.

Background: In the rat, the maintenance of gestation is dependent on progesterone production from the corpora lutea (CL), which are under the control of pituitary, decidual and placental hormones. The luteal metabolism of progesterone during gestation has been amply studied. However, the regulation of progesterone synthesis and degradation during pseudopregnancy (PSP), in which the CL are mainly under the control of pituitary prolactin (PRL), is not well known.

In vivo hormonal environment leads to differential susceptibility of the corpus luteum to apoptosis in vitro.

We evaluated the involvement of the in vivo hormonal environment on the ability of the rat corpus luteum (CL) to undergo apoptosis. Gel electrophoretic DNA fragmentation analysis revealed no apoptosis in CL isolated either the 2 last days of pregnancy (Days 21 and 22) or throughout the 4 days following parturition, suggesting that the number of cells undergoing apoptosis at the same time is not sufficient to allow for visualization of DNA breakdown. In contrast, CL incubated in serum-free medium underwent significant apoptosis, as evaluated by chromatin condensation and DNA fragmentation, regardless of their developmental stage in pregnancy.

Progesterone promotes survival of the rat corpus luteum in the absence of cognate receptors.

Progesterone production by the corpus luteum (CL) is essential for preparation of the endometrium for implantation and for the maintenance of gestation. Progesterone modulates its own production and opposes functional luteal regression induced by exogenous agents, such as prostaglandin F(2alpha). In the present study, we evaluated whether progesterone is also capable of interfering with the process of structural luteal regression, which is characterized by a decrease in weight and size of the gland because of programmed cell death (i.