Effect of Galanin Infusion into the Third Ventricle on Plasma Concentrations of Metabolic Parameters in Goats Fed Diets of Different Energy Content

The goal of this study was to determine whether galanin affects the mean plasma concentrations of metabolic parameters such as thyroxine (T4), triiodothyronine (T3), growth hormone (GH), insulin, glucagon, glucose, fatty acid and urea in goats fed diets differing in energy content. Sixteen goats were randomly divided into 4 groups. Animals in groups 1 and 2 were fed 100% and animals in groups 3 and 4 were fed 50% energy content in the diet for 20 days. After 20 days, animals in groups 1 and 3 received a daily infusion of $1{\mu}g$ galanin and groups 2 and 4 received a daily infusion of $2{\mu}g$ galanin into their third ventricle for 5 days. Blood samples were collected daily from the jugular vein before infusion on day 4 until 4 days after the last infusion of galanin. Samples were assayed for plasma T3, T4, GH, insulin and glucagon concentrations by double-antibody RIA. Glucose, fatty acid and urea concentrations were also measured. Lower dietary energy intake and infusions of 1 and $2{\mu}g$ galanin significantly (p<0.01) decreased the mean plasma concentrations of T3, T4, insulin and glucose and significantly (p<0.01) increased the mean plasma concentrations of GH, glucagon, fatty acid and urea of the animals in groups 3 and 4. Different dosages of the galanin infusions did not change the plasma concentrations of the metabolic parameters in the animals fed a normal dietary energy content. The results of this experiment indicated that galanin may negatively affect T3, T4, insulin and glucose and increase GH, glucagon, fatty acid and urea in goats with negative energy balance, but not in those with positive energy balance.