Effect of 2-aminoethanol on the synthesis, binding, uptake and metabolism of GABA.

2-Aminoethanol (ethanolamine) was studied for effects on neurochemical assays for GABA synthesis, receptor binding, uptake and metabolism in rat brain preparations. The effects of ethanolamine were compared with those of ethanolamine O-sulphate (EOS), an inhibitor of GABA degradation. Furthermore, the effect of both compounds was compared on GABA metabolism in rat brain in vivo. In vitro, ethanolamine and EOS had no significant effect on the GABA synthesizing enzyme glutamic decarboxylase (GAD) and GABA uptake, but both drugs proved virtually equipotent to inhibit the GABA degrading enzyme GABA aminotransferase (GABA-T). EOS was a relatively potent inhibitor of GABA receptor binding, whereas ethanolamine was not effective in this regard. Following systemic administration in rats, 50% inhibition of GABA-T in the brain was achieved by 500 mg/kg ethanolamine or 2000 mg/kg EOS, respectively. As a consequence of GABA-T inhibition, GABA levels increased significantly. GAD activity remained unchanged after both treatments. The present results suggest that the recently reported enhancement of functional effects of GABA by ethanolamine may relate, at least in part, to the inhibitory effect of the compound on GABA catabolism.