Blockade of noradrenergic neurotransmission with diethyldithiocarbamic acid decreases the mRNA level of gonadotropin-releasing hormone in the hypothalamus of ovariectomized, steroid-treated prepubertal rats.

We have previously found that progesterone (P) augmented gonadotropin-releasing hormone (GnRH) mRNA levels in the hypothalamus of ovariectomized, estradiol-treated (OVX + E) prepubertal rats. In order to determine whether noradrenergic neurotransmission is involved in the stimulatory effect of P on GnRH gene expression, diethyldithiocarbamic acid (DDC, 500 mg/kg), a dopamine beta-hydroxylase inhibitor was administered i.p. 1 h before P (1 mg) injection into OVX + E treated rats, and the effect of DDC on the P-induced GnRH mRNA levels was examined. A single injection of P into OVX + E primed rats augmented norepinephrine (NE) content, while the administration of DDC effectively blocked the P-induced increase in NE content, along with the increase in dopamine content. Suppression of NE neurotransmission with DDC resulted in a marked decrease in the P-induced GnRH mRNA levels as well as GnRH release in vitro. These results clearly demonstrate that noradrenergic neurotransmission is involved in P-stimulated GnRH gene expression in the rat hypothalamus.