Feedback effects of growth hormone on anterior pituitary function in chickens

Circulating GH concentrations were suppressed 24 h after intracerebroventricular (i.c.v.) injection of native or recombinant DNA-derived chicken GH (rcGH) (10 micrograms in 4 microliters vehicle) into the right lateral ventricles of conscious 6-week-old cockerels. Plasma concentrations of LH were suppressed within 1 h of i.c.v. administration of GH at doses of 1 or 10 micrograms, and remained suppressed for 24 h in birds injected with the highest concentration of GH. In contrast, concentrations of plasma prolactin were increased 24 h after i.c.v. administration of GH (10 micrograms). The i.v. administration of rcGH (at concentrations of 10 or 100 micrograms/kg) did not mimic the effects of i.c.v. injection of GH. These results demonstrate central effects of GH on pituitary function in the domestic fowl.