LACK OF HORMONAL INFLUENCES ON THE GABAERGIC STIMULATION OF GROWTH-HORMONE SECRETION IN THE NEONATAL RAT

GABA has been shown to stimulate pituitary growth hormone secretion in the neonatal but not in the adult rat (Acs et al. 1984; 1987). The di sapparence of the GH stimulatory effect of GABA was studied in organ-c ultured neonatal pituitaries and in pituitaries from rats treated neon atally with various hormones. The responsiveness of organ-cultured neo natal pituitaries to GABA and to TRH was diminished compared to that o f the littermate controls. Treatment of the neonatal rats with adrenal and sexual steroids or thyroid hormones had no effect on the GABA eli cited pituitary GH secretion. We conclude that the disappearance of GA BAergic stimulation of GH secretion in the postnatal development is no t influenced by the changes in the hormonal environment.