A Study of γ-Aminobutyric Acid (GABA) in Amniotic Fluid

Objective: The purpose of the study was to evaluate the role of gamma aminobutyric acid (GABA), an inhibitory neurotransmitter, in amniotic fluid (AF) during fetal distress, because it has been reported that several neurotransmitters, e.g. norepinephrine, are affected by GABA. Methods: AF was obtained during elective cesarean section (CS, n = 11) and cesarean section due to fetal distress without labor pain (FD, n = 7). Maternal and umbilical-cord blood, as well as the first urine of the neonates, also were collected. GABA, norepinephrine (NE), and epinephrine (EP) concentrations were measured using HPLC. Results: The GABA concentration was higher in the AF than in either maternal or fetal circulation, or in the first urine of neonates. The GABA concentrations in the AF and in the first urine of neonates were significantly higher in the FD group than in the CS group (p < 0.05). Furthermore, significant positive correlations were observed between the NE and GABA concentrations and between the EP and GABA concentrations in the AF. GABA was produced in a time-dependent manner in cultured amnion cells. Conclusion: The highest concentration of GABA was found in the AF. The GABA in the AF appeared to be derived from both the amniotic membrane and the fetal urine. The increase in the GABA concentration in cases of fetal distress might be partially derived from the fetus via fetal urine. The positive correlations between the concentrations of GABA and those of NE and EP in the AF, suggest that GABA, NE, and EP might play important roles during fetal distress.