The Influence of Pharmacological Manipulation of Serotonin on Serum Growth Hormone and Luteinizing Hormone Levels in Young Turkeys (Meleagris gallopavo)

Abstract

Serum growth hormone (GH) and luteinizing hormone (LH) levels were determined by homologous radioimmunoassay in 8 to 10-week-old domestic white turkeys treated by intraperitoneal injection of agents that alter serotonergic activity. The serotonin, 5-hydroxytryptamine (5-HT) precursor, 5-hydroxytryptophan (5-HTP), at doses of 80 and 150 mg/kg, produced a dose-related elevation in serum GH (P=.09) and no change in serum LH (P=.30). Administration of fluoxetine (10 mg/kg), a 5-HT reuptake blocker, produced no change in serum GH or LH. When fluoxetine injection preceded the administration of a nonstimulatory dose of 5-HTP, an elevation in GH was observed, but again no change in LH level was evident. Stimulation of postsynaptic 5-HT receptors with quipazine (.5 to 10.0 mg/kg) resulted in a similar elevation in GH; persistence of the effect was dose dependent. Quipazine administration had no influence on serum LH levels. Administration of methysergide (10 or 25 mg/kg), a 5-HT antagonist, induced no change in either serum GH or LH levels. Serotonergic input appears to stimulate GH release and has no apparent influence on LH release in young turkeys.