Measurement of GABA following GABA-transaminase inhibition by gabaculine: a 1H and 31P NMR spectroscopic study of rat brain in vivo.

A selective 1H 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 pHi were determined by 31P NMR. GABA levels increased approximately linearly (r = 0.81 to 0.94; P < 0.0005) from 1.9 +/- 0.4 mumol/g (pre-gabaculine; mean +/- SD) to between 6 and 8 mumol/g after 4 hr at rates of accumulation of 1.1 to 2.9 mumol/hr/g. 1H NMR spectroscopic measurements of cerebral GABA and its rate of turnover offers a new approach in the study of GABA-mediated processes in vivo.