Dose-related effects of γ-amino β-hydroxy butyric acid (GABOB) infusion on growth hormone secretion in normal women

The effect of γ-aminoβ-hydroxy butyric acid (GABOB) infusion on GH secretion has been investigated in 3 groups of 6 normal women. Different doses (100 mg/min, 20 mg/min, 3.5 mg/min) of GABOB diluted with normal saline solution were infused iv over a 20 min period and compared with control tests performed using only saline solution. The infusions with GABOB at the doses of 100 mg/min and 20 mg/min were followed by a significant rise (p<0.01) in GH plasma levels, in comparison to control tests. The quantitative GH secretion after 100 mg/min GABOB infusion was significantly greater (p< 0.05) in comparison with quantitative GH secretion after 20 mg/min GABOB infusion. After 3.5 mg/min infusion, only 3 out of 6 subjects showed an increase in the hormone concentrations. The acute injection with sulpiride (5 mg iv, bolus), performed either before or after the start of GABOB infusion, failed to affect GH response to GABOB. These results show that GABOB infusion induce a dose-dependent rise in GH plasma levels in normal women. The dopaminergic system does not seem to be involved in this effect.