The Central Effect of β‐Endorphin and Naloxone on The Biosynthesis of GnRH and GnRH Receptor (GnRHR) in The Hypothalamic‐Pituitary Unit of Follicular‐Phase Ewes

Abstract

The effects of prolonged, intermittent infusion of β-endorphin or naloxone into the third cerebral ventricle of follicular-phase ewes on the expression of genes encoding GnRH and GnRHR in the hypothalamus and GnRHR in the anterior pituitary gland (AP) were examined by an enzyme-linked immunoabsorbent assay. Activation or blockade of μ-opioid receptors significantly decreased or increased the GnRH concentration and GnRHR abundance in the hypothalamus, respectively, and affected in the same way GnRHR quantity in the AP gland. The changes in the levels of GnRH and GnRHR after treatment with β-endorphin as well as following action of naloxone were reflected in fluctuations of plasma LH concentrations. On the basis of these results, it is suggested that β-endorphinergic system in the hypothalamus of follicular-phase ewes affects directly or via β-endorphin-sensitive interneurons GnRH and GnRHR biosynthesis leading to suppression in secretory activity of the hypothalamic-pituitary axis.

Effect of hypothyroidism on the hypothalamic–pituitary–ovarian axis and reproductive function of pregnant rats

“…The release of GnRH from approximately 1000 neurons within the hypothalamus in a pulsatile manner, which is characteristic of postnatal development in primates, is largely independent of the gonad [ 9 ]. Although the switch of pulsatile GnRH discharge leading to the recurrence of puberty has been researched widely, few studies have explored the causes of the inhibition of the GnRH pulse generators at the start of youth.…”