Third ventricle neuropeptide-Y infusion effect on metabolic parameters under different energy levels in diets

Abstract

The goal of this study was to determine whether neuropeptide-Y 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 the goats fed different energy content in diets. 16 goats were randomly divided into four groups. Animals in groups 1 and 2 were fed 100% energy content in diet and animals in groups 3 and 4 were fed 50% energy content in diet for 20 days. After 20 days, animals in groups 1 and 3 received daily infusion of 1 μg neuropeptide-Y and groups 2 and 4 received daily infusion of 2 μg galanin into their third ventricle for 5 days. Blood samples were collected daily from the jugular veins before infusions on day 4 until 4 days after the last infusions of neuropeptide-Y. Samples were assayed for plasma T3, T4, GH, insulin and glucagon concentrations by double-antibody radioimmunoassay (RIA). Glucose, fatty acid and urea concentrations were also measured. Lower dietary energy intake and infusions of 1 and 2 μg neuropeptide-Y 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 neuropeptide-Y infusions did not change the plasma concentrations of the metabolic parameters in the animals fed normal energy content in diets. The results of this experiment indicate that neuropeptide-Y may negatively affected T3, T4, insulin and glucose and increased GH, glucagon, fatty acid and urea in the goats with negative energy balance, but not in those with the positive energy balance.

Keywords: Neuropeptide-Y, metabolic hormones, goat, energy balance

African Journal of Biotechnology Vol. 12(13), pp. 1523-1532