Effect of High Energy Intake and Treatment with Galanin on Gonadotropin Levels in Female Goats

Background: Galanin is an orexigenic agent and has been demonstrated to be a putative regulator of gonadotropin secretion. It is well known that this orexigenic peptide probably plays a vital role in the regulation of reproduction; however, the underlying mechanisms have not been fully elucidated. Objectives: The goal of this study was to determine the role of galanin in the regulation of gonadotropins in goats, which were subjected to either high or low energy diets. Materials and Methods: Adult female Saanen goats were randomly divided into 2 groups. Animals in the two groups were fed either a 100% or a 150% energy content diet, respectively, for a month. On the first day of the experiment, all animals received an intravenous injection of 1 μg galanin/kg body weight. On the second day, each animal was administered 2 μg galanin/kg body weight. Blood samples were withdrawn by jugular venipuncture at 30-minute intervals, 3.5 h before and 3.5 h after galanin injection. In order to determine the concentration of LH and FSH, plasma was isolated and subjected to radioimmunoassay in order to determine the concentrations of relevant gonadotropin hormones. Results: The intravenous administration of 1 μg galanin/kg body weight to goats who were subjected to a high-energy feed significantly reduced circulating LH and FSH levels. It contrast, this dose had no effect on goats subjected to the lower energy diet. The injection of galanin at a dose of 2 μg/kg body weight had no influence on mean plasma concentrations of gonadotropins in goats fed either of the two diets. Conclusions: The results indicate that galanin is not a principal hypophyseal regulator in the secretion of gonadotropins in Saanan goats. It may be inferred that in the same animal model galanin has a gonadotropin-reducing effect when its in vivo concentration increases.