Premium
Oestrogen Receptor‐α and ‐β Immunoreactivity in Gonadotropin‐Releasing Hormone Neurones after Ovariectomy and Chronic Exposure to Oestradiol
Author(s) -
Legan S. J.,
Tsai H.W.
Publication year - 2003
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.1365-2826.2003.01115.x
Subject(s) - medicine , endocrinology , ovariectomized rat , gonadotropin releasing hormone , luteinizing hormone , gonadotropin , immunocytochemistry , estrogen , receptor , hormone , hypothalamus , biology , chemistry
Oestradiol exerts negative‐ and positive‐feedback actions on luteinizing hormone (LH) secretion by modulating gonadotropin‐releasing hormone (GnRH) release. Furthermore, a chronic increase in circulating oestradiol in either young ovariectomized (OVX) rats, or in middle‐aged persistent oestrous (PE) rats, causes a gradual attenuation of LH surges until the positive‐feedback action of oestradiol disappears. Based on these findings, and on the equivocal evidence regarding a direct action of oestradiol on GnRH neurones, we tested the hypothesis that chronic oestradiol abolishes LH surges by decreasing the proportion of GnRH neurones containing oestrogen receptor (ER)α or β. Regularly cycling rats were ovariectomized, and half immediately received oestradiol. Three days, or 2 or 4 weeks later, rats were perfused at 18.00 h, and GnRH was colocalized with ERα or ERβ by immunocytochemistry. ERβ was expressed in 76% of GnRH neurones, whereas virtually no GnRH cells were immunopositive for ERα. The proportion of GnRH cells expressing ERα or β in OVX rats was not altered by oestradiol or time after OVX, and this was the case regardless of their medial to lateral, or rostral to caudal location. The results indicate that the mechanisms for the positive‐feedback action of oestradiol, and the loss of LH surges in OVX rats after chronic oestradiol, are not mediated by changes in the proportion of oestrogen‐receptor containing GnRH neurones.