GALANIN COUNTERACTS THE INHIBITORY EFFECTS OF GLUCOCORTICOIDS ON GROWTH-HORMONE SECRETION IN THE RAT

The aim of our study was to investigate the effect of galanin on basel ine and growth hormone (GH) releasing hormone (GHRH)-stimulated GH con centrations in conscious, freely moving rats receiving long-term gluco corticoid treatment. Animals were treated for 7 days with an intraperi toneal injection of either Vehicle or dexamethasone ([dex] 40 mu g/d). Rats underwent the following experimental trials: at -15 minutes anim als received an intravenous injection of saline or galanin (12.5 mu g/ kg), and at 0 minutes rats received a second intravenous injection of saline or rat GHRH (500 ng/kg). Blood samples were drawn every 5 minut es from -15 to +15 minutes and then at 30 minutes. The GH response to saline + GHRH atone was significantly higher (P < .05) in chronically vehicle-treated rats as compared with chronically dex-treated ones. In contrast, galanin + saline increased serum GH levels in a similar fas hion in both chronically vehicle- and dex-treated rats. The response t o galanin + GHRH was similar to galanin + saline in chronically vehicl e treated rats, but was significantly enhanced in chronically dex-trea ted rats. These results suggest that galanin-mediated GH release in ra ts may involve somatostatinergic pathways. Copyright (C) 1995 by W.B. Saunders Company