Naloxone does not alter the effect of gamma aminobutyric acid derivative, baclofen, on GH release in man.

To evaluate the interaction between opioid peptides and GABAergic system in regulating GH secretion we administered 5 mg of baclofen, a GABA derivative, to eight normal male subjects. The results were compared to those obtained in the same subjects treated with naloxone (10 mg/2 h) plus baclofen. GH levels increased significantly above basal value either after baclofen and naloxone plus baclofen without any significant difference between GH responses during the two tests. It is suggested that the two substances do not act at the level of the same receptor site. The evaluation of a possible interaction between opioid peptides and GABAergic system on GH release requires further investigation.