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Neonatal handling and reproductive function in female rats
C M Gomes1, C Raineki, P Ramos de Paula
1Laboratório de Neuroendocrinologia do Comportamento, Departamento de Fisiologia, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
The Journal of Endocrinology
|February 3, 2005
Summary
Early-life handling in rats disrupts reproductive hormones, leading to anovulatory cycles and reduced sexual receptivity. This early stimulation impacts the hypothalamus-pituitary-gonad axis long-term.
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Developmental Programming
Background:
- Neonatal handling in rats is known to affect reproductive functions.
- Hormonal balance, including estradiol (E2), progesterone (P), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL), is crucial for estrous cycles and sexual receptivity.
- The hypothalamus-pituitary-gonad (HPG) axis regulates these reproductive processes.
Purpose of the Study:
- To investigate the long-term effects of neonatal handling on reproductive hormone levels throughout the estrous cycle.
- To assess plasma levels of E2, P, LH, FSH, and PRL in adult rats exposed to neonatal handling.
- To determine the LHRH content in specific brain regions (MPOA, ME, MSA) of handled rats.
Main Methods:
- Wistar rat pups were subjected to daily brief handling or left undisturbed from birth for 10 days.
- Adult rats had blood samples collected for hormone analysis (RIA).
- Brain regions (MPOA, ME, MSA) were microdissected for LHRH content determination via RIA.
Main Results:
- Neonatal handling resulted in fewer oocytes on estrus day.
- Handled rats showed reduced E2 levels on proestrus and decreased P levels on metestrus and estrus.
- Plasma LH, FSH, and PRL levels were lower in handled rats during proestrus, while MPOA LHRH content was elevated.
Conclusions:
- Reduced E2, LH, FSH, and LHRH secretion during proestrus likely explains the anovulatory cycles in neonatally handled rats.
- Decreased PRL secretion may contribute to reduced sexual receptivity in these females.
- Early-life environmental stimulation can induce lasting alterations in the HPG axis function.