title: Prolactin activates mitogen-activated protein kinase signaling and corticotropin releasing hormone transcription in rat hypothalamic neurons.
abstract: Prolactin (PRL) modulates maternal behavior and mediates hypothalamic pituitary adrenal axis inhibition during lactation via PRL receptors in the brain. To identify mechanisms mediating these effects, we examined the effects of PRL on signaling and CRH transcription in hypothalamic neurons in vivo and in vitro. Western blot of hypothalamic proteins from rats receiving intracerebroventricular PRL injection revealed increases in phosphorylation of the MAPK and ERK. Double-staining immunohistochemistry demonstrated phosphorylated ERK localization in parvocellular CRH neurons as well as magnocellular vasopressin and oxytocin neurons of the hypothalamic paraventricular (PVN) and supraoptic nuclei. PRL also induced ERK phosphorylation in vitro in the hypothalamic cell line, 4B, which expresses PRL receptors, and in primary hypothalamic neuronal cultures. Using reporter gene assays in 4B cells, or quantitative RT-PCR for primary transcript in hypothalamic cell cultures, PRL potentiated forskolin-stimulated CRH transcription through activation of the ERK/MAPK pathway. The effect of PRL in hypothalamic cell cultures was unaffected by tetrodotoxin, suggesting a direct effect on CRH neurons. The data show that PRL activates the ERK/MAPK pathway and facilitates CRH transcription in CRH neurons, suggesting that the inhibitory effect of PRL on hypothalamo-pituitary-adrenal axis activity reported in vivo is indirect and probably mediated through modulation of afferent pathways to the PVN. In addition, the prominent stimulatory action of PRL on the ERK/MAPK pathway in the hypothalamic PVN and supraoptic nucleus is likely to mediate neuroplasticity of the neuroendocrine system during lactation.
authors.affiliation: Department of Behavioural and Molecular Neuroendocrinology, Institute of Zoology, University of Regensburg, 93053 Regensburg, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Blume
authors.forename: Luz
authors.initials: L
authors.lastname: Torner
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Sivan
authors.initials: S
authors.lastname: Subburaju
authors.forename: Greti
authors.initials: G
authors.lastname: Aguilera
authors.forename: Inga D
authors.initials: ID
authors.lastname: Neumann
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D003346:Corticotropin-Releasing Hormone / Q000235:genetics*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D007031:Hypothalamus / Q000166:cytology* / Q000378:metabolism; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D016133:Polymerase Chain Reaction; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D011388:Prolactin; D003346:Corticotropin-Releasing Hormone; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases