title: Region-, neuron-, and signaling pathway-specific increases in prolactin responsiveness in reproductively experienced female rats.
abstract: Pregnancy and lactation cause long-lasting enhancements in maternal behavior and other physiological functions, along with increased hypothalamic prolactin receptor expression. To directly test whether reproductive experience increases prolactin responsiveness in the arcuate, paraventricular, and supraoptic nuclei and the medial preoptic area, female rats experienced a full pregnancy and lactation or remained as age-matched virgin controls. At 5 wk after weaning, rats received 2.5, 100, or 4000 ng ovine prolactin or vehicle intracerebroventricularly. The brains underwent immunohistochemistry for the phosphorylated forms of signal transducer and activator of transcription 5 (pSTAT5) or ERK1/2 (pERK1/2). There was a marked increase in pSTAT5 and pERK1/2 in response to prolactin in the regions examined in both virgin and primiparous rats. Primiparous rats exhibited approximately double the number of prolactin-induced pSTAT5-immunoreactive cells as virgins, this effect being most apparent at the higher prolactin doses in the medial preoptic area and paraventricular and supraoptic nuclei and at the lowest prolactin dose in the arcuate nucleus. Dual-label immunohistochemistry showed that arcuate kisspeptin (but not oxytocin or dopamine) neurons displayed increased sensitivity to prolactin in reproductively experienced animals; these neurons may contribute to the reduction in prolactin concentration observed after reproductive experience. There was no effect of reproductive experience on prolactin-induced pERK1/2, indicating a selective effect on the STAT5 pathway. These data show that STAT5 responsiveness to prolactin is enhanced by reproductive experience in multiple hypothalamic regions. The findings may have significant implications for understanding postpartum disorders affecting maternal care and other prolactin-associated pathologies.
authors.affiliation: Centre for Neuroendocrinology and Department of Anatomy and Structural Biology, University of Otago School of Medical Sciences, Dunedin, New Zealand.
authors.forename: Annika
authors.initials: A
authors.lastname: Sjoeholm
authors.forename: Robert S
authors.initials: RS
authors.lastname: Bridges
authors.forename: David R
authors.initials: DR
authors.lastname: Grattan
authors.forename: Greg M
authors.initials: GM
authors.lastname: Anderson
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000378:metabolism; D005260:Female; D006624:Hippocampus / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D007031:Hypothalamus / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D057967:Infusions, Intraventricular; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism; D010298:Parity / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D011247:Pregnancy; D011301:Preoptic Area / Q000166:cytology / Q000378:metabolism; D011388:Prolactin / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012098:Reproduction / Q000502:physiology; D050799:STAT5 Transcription Factor / Q000378:metabolism; D012756:Sheep; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D013495:Supraoptic Nucleus / Q000166:cytology / Q000378:metabolism; D013997:Time Factors
chemical_list: D050799:STAT5 Transcription Factor; D011388:Prolactin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3