Regulation of galanin and gonadotropin-releasing hormone gene expression in the hypothalamus and basal forebrain of the rat

Hormones and Behavior
E Grafstein-DunnRobert A Steiner

Abstract

Galanin is a cotransmitter in GnRH neurons and is thought to play a role in the control of gonadotropin secretion. The aim of our research has been to learn how galanin mRNA is regulated in GnRH neurons with the goal of understanding galanin's physiological significance. We have used double-label in situ hybridization and computerized image analysis to identify GnRH neurons coexpressing galanin mRNA and to estimate cellular levels of galanin message in these cells under different physiological conditions in the rat. In adult females, levels of galanin mRNA in GnRH neurons increase two- to fourfold with the onset of the proestrous and steroid-induced LH surges. Pharmacological blockade of synaptic transmission with either a general anesthetic (pentobarbital) or an alpha-adrenergic receptor antagonist (phenoxybenzamine) inhibits both the steroid-induced LH surge and the associated induction of galanin expression in GnRH neurons. Compared with the day of diestrus of the estrous cycle, during lactation cellular levels of galanin mRNA in GnRH neurons are profoundly reduced. In contrast to galanin mRNA in GnRH neurons, we could adduce no evidence for changes in cellular levels of GnRH mRNA under any physiological conditions or with a...Continue Reading

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