Neonatal handling and reproductive function in female rats

Abstract

Neonatal handling induces anovulatory estrous cycles and decreases sexual receptivity in female rats. The synchronous secretion of hormones from the gonads (estradiol (E 2 ) and progesterone (P)), pituitary (luteinizing (LH) and follicle-stimulating (FSH) hormones) and hypothalamus (LH-releasing hormone (LHRH)) are essential for the reproductive functions in female rats. The present study aimed to describe the plasma levels of E 2 and P throughout the estrous cycle and LH, FSH and prolactin (PRL) in the afternoon of the proestrus, and the LHRH content in the medial preoptic area (MPOA), median eminence (ME) and medial septal area (MSA) in the proestrus, in the neonatal handled rats. Wistar pup rats were handled for 1 min during the first 10 days after delivery (neonatal handled group) or left undisturbed (nonhandled group). When they reached adulthood, blood samples were collected through a jugular cannula and the MPOA, ME and MSA were microdissected. Plasma levels of the hormones and the content of LHRH were determined by RIA. The number of oocytes counted in the morning of the estrus day in the handled rats was significantly lower than in the nonhandled ones. Neonatal handling reduces E 2 levels only on the proestrus day while P levels decreased in metestrus and estrus. Handled females also showed reduced plasma levels of LH, FSH and PRL in the afternoon of the proestrus. The LHRH content in the MPOA was significantly higher than in the nonhandled group. The reduced secretion of E 2 , LH, FSH and LHRH on the proestrus day may explain the anovulatory estrous cycle in neonatal handled rats. The reduced secretion of PRL in the proestrus may be related to the decreased sexual receptiveness in handled females. In conclusion, early-life environmental stimulation can induce long-lasting effects on the hypothalamus-pituitary-gonad axis .

Neonatal Experiences Differentially Influence Mammary Gland Morphology, Estrogen Receptor α Protein Levels, and Carcinogenesis in BALB/c Mice

“…However, others have shown that neonatal handling alters hormone secretion patterns of the adult rat estrous cycle (e.g., reduced estradiol secretion relative to nonhandled controls during proestrus; ref. 35). The hormonal variations during the estrus cycle influence the balance of proliferation and apoptosis in the mammary epithelium (36).…”

Efeitos da depressão materna no desenvolvimento neurobiológico e psicológico da criança

“…Handling increases pup vocalizations, which have, in turn, been associated with increased maternal licking. 38 Lucion et al, 39 Gomes et al, 40 Severino et al 41 and others were the first to demonstrate that neonatal stress alters reproductive mechanisms in the adult life. Lucion et al 39 demonstrated that neonatal handling reduces the number of cells in the locus coeruleus of rats in about 35%.…”

Effects of Neonatal Handling on Central Noradrenergic and Nitric Oxidergic Systems and Reproductive Parameters in Female Rats

“…In adult rats, neonatal handling reduces fearfulness to novel and aversive environments [4, 5] and stress responses to a wide variety of stressors [6,7,8]. Moreover, neonatal handling procedure, which involves repeated brief maternal separations followed by experimental manipulations, reduces the sexual behavior of male and female rats [5, 9], daily sperm production [10], and, in females, it induces anovulatory estrous cycles [11, 12]. On the afternoon of proestrus, neonatally handled females show increased content of gonadotropin-releasing hormone (GnRH) in the medial preoptic area (MPOA) and reduced plasma concentrations of estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin [12].…”