The Journal of Neuroscience, April 15, 1999, 19(8):3213-3222
Hormonal Regulation of Glutamate Receptor Gene Expression in the
Anteroventral Periventricular Nucleus of the Hypothalamus
Guibao
Gu1,
Frederique
Varoqueaux1, and
Richard B.
Simerly1, 2
1 Division of Neuroscience, Oregon Regional Primate
Research Center, Beaverton, Oregon 97006, and 2 Program in
Neuroscience, Oregon Health Sciences University, Portland, Oregon
97201
Glutamate plays an important role in mediating the positive
feedback effects of ovarian steroids on gonadotropin secretion, and the
preoptic region of the hypothalamus is a likely site of action of
glutamate. The anteroventral periventricular nucleus (AVPV) of the
preoptic region is an essential part of neural pathways mediating
hormonal feedback on gonadotropin secretion, and it appears to provide
direct inputs to gonadotropin releasing hormone (GnRH)-containing
neurons. Immunohistochemistry and in situ hybridization were used in this study to define the distribution and hormonal regulation of glutamate receptor subtypes in the AVPV of juvenile female rats. Neurons that express the NMDAR1 receptor subtype are
abundant in the AVPV, as are cells that express AMPA receptor subtypes
(GluR1, GluR2, and GluR3 but not GluR4), and the AVPV appears to
contain a dense plexus of NMDAR1-immunoreactive presynaptic terminals.
However, AVPV neurons do not seem to express detectable levels of
kainate receptor (GluR5, GluR6, and GluR7) or metabotropic receptor (mGluR1-6) subtypes. Treatment of ovariectomized juvenile rats with estradiol induced expression of GluR1 mRNA but did not alter
levels of GluR2 or GluR3 mRNA. Treatment of estrogen-primed ovariectomized juvenile rats with progesterone caused an initial increase in GluR1 mRNA expression, followed by a small decrease 24 hr
after treatment. In contrast, estrogen appears to suppress levels of
NMDAR1 mRNA in the AVPV, which remained unchanged after progesterone treatment. Thus, one mechanism whereby ovarian
steroids may provide positive feedback to GnRH neurons is by altering
the sensitivity of AVPV neurons to glutamatergic activation.
Key words:
preoptic region; gonadotropin releasing hormone; in
situ hybridization; ovarian steroids; progesterone; estrogen
Copyright © 1999 Society for Neuroscience 0270-6474/99/1983213-10$05.00/0