We examined by Real-time PCR how prolonged inhibition of dopaminergic D-2 receptors
(DA-2) in the hypothalamus of anestrous ewes by infusion of sulpiride into the third
cerebral ventricle affected GnRH and GnRH-R gene expression in discrete parts of this
structure and GnRH-R gene expression in the anterior pituitary. Blockaded DA-2 receptors
significantly decreased GnRH mRNA levels in the ventromedial hypothalamus but did
not evidently affect GnRH mRNA in the preoptic/anterior hypothalamic area. Blockaded
DA-2 receptors led to different responses in GnRH-R mRNA in various parts of the hypothalamus;
increased GnRH-R mRNA levels in the preoptic/anterior hypothalamic area, and decreased
GnRH-R mRNA amounts in the ventromedial hypothalamus stalk/median eminence. An infusion
of sulpiride into the III-rd ventricle increased GnRH mRNA levels in the anterior
pituitary gland and LH secretion. It is suggested that the increase of GnRH gene expression
in the anterior pituitary gland and LH secretion in sulpiride-treated ewes are related
with an increase of biosynthesis GnRH with concomitant decreased biosynthesis of GnRH-R
protein in the ventromedial hypothalamus/stalk median eminence allowing to an increase
of GnRH release.
receptors - signal transduction - luteininzing hormone - hormones - gonadotrophins
- hormones
