Pituitary galaninergic system activity in female rats: the regulatory role of gonadal steroids.

The well-recognized sensitivity of the galanin gene in the anterior pituitary gland to estrogen suggests that estrogen receptor activity may influence the galaninergic system through modulation of galanin receptor (GALR) gene expression. Here, we evaluated the following: (i) the effects of estrogen on GALR mRNA expression; (ii) the estrogen receptor subtype that is specifically involved in this activity; and (iii) the effects of progesterone in the absence or presence of estrogen on galanin concentration in anterior pituitary gland. In the first experiment, ovariectomized 4-month-old rats were pre-treated subcutaneously with 17β-estradiol (3 x 20 μg), the ESR1 (ERα) agonist propyl pyrazole triol (PPT) (3 x 5 mg), and the ESR2 (ERβ) agonist diarylpropionitrile (DPN) (3 x 0.

The effect of valproate (VPA) treatment on inositol phosphates (IPs) accumulation in non-stimulated and GnRH-treated female rat anterior pituitary cells in vitro.

Objective: Mechanism(s) responsible for VPA-induced effects on reproductive axis activity are not fully recognized. Previously we reported that VPA suppressed only GnRH-stimulated but not the basal LH release from rat anterior pituitary (AP) cells in vitro. Since the inhibitory effect of VPA was exerted only in GnRH-activated cells, potential VPA impact on GnRH-R-coupled IP3/PKC signaling could not be excluded.

The evaluation of estradiol and leptin action on the activity of the somatotropic and gonadotropic axes in peripubertal female rats.

Objective: Available data suggest that estrogens and leptin play a role in the control of the pubertal process. In humans and some mammal species the increase of the activity of gonadotropic axis accompanies the decrease in the rate of growth at puberty. The effect of 17β-estradiol and/or leptin administration on the somatotropic and gonadotropic axes was studied using prepubertal female rats as an animal model.

Valproate inhibits GnRH-induced gonadotropin release from anterior pituitary cells of male rat in vitro.

Objective: Valproate (VPA) a potent antiepileptic drug has been claimed to induce reproductive disturbances in men. Long-term VPA treatment can affect sperm morphology and induce testicular atrophy in non-epileptic rats. It has been reported that VPA reduced testosterone secretion stimulated by hCG in isolated rat Leydig cells.

Orexin A and its role in the regulation of the hypothalamo-pituitary axes in the rat.

Orexin A (OxA), a recently discovered neuropeptide, is synthesized mainly by neurons located in the posterolateral hypothalamus and is a 33 amino acid peptide with N-terminal pyroglutamyl residue and two inter-chain disulfide bonds. It is a potent agonist for both the orexin-1 (OxR1) and orexin-2 (OxR2) receptors. Orexin A and its receptors are widely distributed in the central nervous system (CNS) and peripheral organs suggesting the pleiotropic functions of this peptide.