Search

Intravenous administration of 0.025, 0.25, or 2.5 micrograms/kg thyrotropin releasing hormone (TRH) to 4-week-old female turkeys induced a dose-dependent increase (P = 0.004) in serum prolactin (PRL) 15 min post-treatment. Dispersed anterior pituitary cell cultures were utilized to determine the effect of TRH on cellular release of PRL, luteinizing hormone (LH), and growth hormone (GH). In the first experiment, cells from 13-week-old male turkeys were initially incubated for 24 hr in Medium 199 (M-199) plus 10% turkey serum and then placed in M-199 plus 10(-10) to 10(-4) M TRH for 5 hr. Incubation with TRH produced no change in PRL release from that of spontaneous release (P = 0.854). However, 10(-5) and 10(-4) M TRH induced LH release (P less than 0.0001). The TRH-induced GH response was parabolic (P less than 0.0001), with the maximal release at 10(-8) M. The second experiment, utilizing pituitary cells from 7-week-old females, studied these responses on 3, 5, and 7 days of monolayer incubation. TRH failed to induce a PRL release in all tests (P greater than 0.162), although hypothalamic extract induced a large release (P less than 0.0001) of PRL each time. Both 10(-6) and 10(-4) M TRH induced a LH release on Day 3 while only 10(-4) M did so on Day 5, and none of the doses elicited a release on Day 7. The parabolic GH response generally persisted in all tests.(ABSTRACT TRUNCATED AT 250 WORDS)

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.