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Regulation of Galanin Receptor GalR1 mRNA Expression by Ovarian Steroids in Oestrogen Receptor Alpha‐Immunoreactive Neurones: Identification of Distinct Populations of Neurones in the Preoptic Area
Author(s) -
Mitchell V.,
Lecompte F.,
Beauvillain J. C.
Publication year - 2004
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.0953-8194.2004.01147.x
Subject(s) - medicine , endocrinology , biology , preoptic area , in situ hybridization , estrogen receptor alpha , galanin , ovariectomized rat , estrogen , estrogen receptor , hypothalamus , receptor , neuropeptide , messenger rna , biochemistry , cancer , gene , breast cancer
This study examined whether gonadal steroids are involved in regulating galanin receptor 1 (GalR1) mRNA expression in neurones that contain oestrogen receptor alpha (ERα), in three regions of the preoptic area (POA) known to be involved in the control of gonadotropin secretion. Double‐labelling immunohistochemistry using an antibody against the ERα and in situ hybridization experiments using a 35 S‐labelled riboprobe specific for GalR1 mRNAs revealed that ERα is expressed in a large proportion of GalR1 mRNA‐expressing neurones of the POA in the ovariectomized (OVX) female rat. Oestradiol (E 2 ) and oestradiol plus progesterone (E 2 + P) treatments of OVX rats significantly decreased the proportion of GalR1 mRNA/ERα immunoreactive (ERα‐IR) neurones in the anteroventral periventricular nucleus (AVPV), medial preoptic nucleus (MPN) and medial preoptic area (MPO). The expression of GalR1 mRNA in ERα‐IR neurones varied according the hormonal status of the female animals. In the AVPV, during the oestrous cycle, the hybridization signal significantly increased at oestrus. E 2 and E 2 + P treatments of OVX rats did not induced significant variation of levels of GalR1 mRNAs in ERα‐IR neurones. In the MPN, E 2 treatment of OVX rats resulted in significant increase in GalR1 mRNA expression in ERα‐IR neurones. Similarly, levels of the GalR1 hybridization signal increased during afternoon of proestrus and oestrus. In the MPO, treatment of OVX rats with E 2 + P significantly decreased GalR1 mRNA expression in ERα‐IR neurones. The expression of GalR1 mRNA did not change during the oestrous cycle in this area. These findings suggest that the hypothalamic action of galanin on gonadotopin‐releasing hormone (GnRH) secretion may pass through the specific population of GalR1/ERα‐IR neurones of the MPN in mediating the oestrogen action on the GnRH system at the moment of the luteinizing hormone surge.