MEASUREMENT OF GABA FOLLOWING GABA-TRANSAMINASE INHIBITION BY GABACULINE - A H-1 AND P-31 NMR SPECTROSCOPIC STUDY OF RAT-BRAIN IN-VIVO

A selective H-1 NMR spin-echo editing method was used to detect the 4-CH2 of GABA In rat brain in vivo before and after intravenous administration of the highly selective GABA transaminase inhibitor, gabaculine (3-amino-2,3-dihydrobenzoic acid-HCl; 100 mg/kg, intravenously). The effects of the inhibitor on high energy phosphates and pH(1) were determined by P-31 NMR. GABA levels increased approximately linearly (r = 0.81 to 0.94; P < 0.0005) from 1.9 +/- 0.4 mu mol/g (pre-gabaculine; mean +/- SD) to between 6 and 8 mu mol/g after 4 hr at rates of accumulation of 1.1 to 2.9 mu mol/hr/g. H-1 NMR spectroscopic measurements of cerebral GABA and its tate of turnover offers a new approach in the study of GABA-mediated processes in vivo.