Sex differences in the effect of prepubertal GALP infusion on growth, metabolism and LH secretion.
The hypothalamic neuropeptide, galanin-like peptide (GALP), is known to have an effect on energy expenditure and reproduction in adult male rats, but little work has been done on prepubertal rats. We hypothesized that hypothalamic GALP is involved in physiological changes associated with the onset of puberty. To test this hypothesis, we first determined the postnatal ontogeny of GALP gene expression via in situ hybridization of developing male and female rat pups through adulthood. GALP gene expression was not observed in either male or female rat pups until after postnatal day (PND) 10 and did not reach adult-like levels until after weaning (PND25). To determine if exogenous GALP could induce the onset of puberty, PND25 male and female rats were implanted with lateral ventricular cannulas connected to an osmotic minipump that delivered either GALP or vehicle. GALP infusion significantly (p<0.05) increased body weight, food intake, and metabolic rate in male but not female rats compared to control infusion. After 2 weeks, GALP infusion had no significant effect on the onset of puberty, percent body fat, nor plasma levels of insulin, FSH or gonadal steroids in either sex; however, GALP did significantly (p<0.05) increase plasma levels of LH and leptin in male but not female rats and increased plasma growth hormone (GH) in both sexes. Our observations further demonstrate a sex difference in GALP responsiveness in prepubertal rats. These data suggest that GALP may be involved with the prepubertal increase in circulating leptin, LH, and GH resulting in an increase in metabolic rate and lean growth associated with puberty.
Rich
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Biology Department, Hope College, 35 East 12th Street, Schaap Science Center 3065, Holland, MI 49423, United States.
Reyes
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Reap
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Goswami
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Fraley
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D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D005260:Female; D044089:Galanin-Like Peptide / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D048788:Growth and Development / Q000187:drug effects*; D015918:Infusion Pumps, Implantable; D020547:Lateral Ventricles / Q000187:drug effects; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D053858:Metabolic Networks and Pathways / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D051381:Rats; D020318:Rats, Long-Evans; D012727:Sex Characteristics
D044089:Galanin-Like Peptide; D007986:Luteinizing Hormone