Biogenic amine control of growth hormone secretion in the fetal and neonatal rat

The development of the hypothalamic-pituitary axis for growth hormone (GH) secretion has been studied in th rat fetus and in the neonate 4, 24, 48 and 72 h after birth. Injections of the serotonin blocker cyproheptadine (Cypro) and a catecholamine, dopamine (DA), each led to reductions in the level of serum GH in 21 to 22 day fetuses and in neonates upt to 3 days after birth. The O-methylated derivative of dopamine, dimethoxyphenylethylamine (DMPEA), did not alter serum GH levels from those seen in saline-treated control animals. These results indicate that biogenic amines exert control over GH secretion in the fetus, close to term, and in the early neonatal period. They suggest that this control is similar to that seen in the adult rat and in man and that such control may operate through serotonin receptors.