Endocrine Abstracts

Excitatory amino acid neurotransmitters (EAA) play an essential role in regulation of GH secretion in the central nervous system. Involvement of EAA path way in the secretion of GH was indicated by early finding that NMA stimulate GH secretion via direct release of hypothalamic GHRH. The present study was designed to investigate the involvement of excitatory amino acid neurotransmitter’s (EAA) pathway in the regulation of basal as well as stimulated GH secretion in primates. Four adult male Rhesus monkeys (Macaca mulata) were used in the study. Four sets of experiment were performed. In each experiment all the four animals were bled for a period of 3 h (−60–120 min) at 15 min interval. In first three sets of experiments at 0 min, saline (5 ml/animal), Mk-801 (0.1 mg/kg, BW dissolved in 5 ml saline) and insulin (1.05 μ/kg=255 pl/kg) injections were given. While in the fourth set of experiment the animals were administered an injection of insulin (bolus) immediately following by an injection of MK-801. Plasma levels of GH were determined in duplicate using human Double Antibody Radio Immunoassay (RIA) Kit. Results showed that saline infusion caused no significant change in basal plasma GH concentrations. Administration of MK-801 decreased plasma GH concentrations significantly (P<0.001) over the basal levels. Insulin treatment (bolus) significantly (P<0.00.1) increased the GH profile. While insulin when given in combination with MK-801 significantly (P<0.001) increased plasma GH concentrations. In conclusion the findings of present study confirm that in primates the endogenous excitatory amino acids neurotransmitters are involved in the regulation of basal GH secretions but insulin-stimulated GH secretion may involve the pathway other than EAA.