AMPHETAMINE RELEASES GABA IN STRIATUM OF THE FREELY MOVING RAT - INVOLVEMENT OF CALCIUM AND HIGH-AFFINITY TRANSPORTER MECHANISMS

Using microdialysis the effect was investigated of amphetamine (AMPH) infusions into the striatum on the release of GABA in the freely movin g rat. AMPH (5, 10 and 20 mu g/l), infused through a microdialysis pro be at the rate of 2.5 mu l/min, produced a dose-related increase in ex tracellular concentrations of GABA. At the highest dose (20 mu g/mu l) , AMPH increased GABA from 0.08 +/- 0.01 to 0.67 +/- 0.14 mu M. Increa ses in extracellular GABA produced by AMPH were both calcium-dependent and high affinity GABA transporter-mediated. A medium free of calcium reduced the increase of extracellular GABA produced by AMPH by 37%. N ipecotic acid (2, 4 and 8 mM), a specific GABA re-uptake blocker, sign ificantly attenuated increases in extracellular GABA, but not GLU, pro duced by AMPH (20 mu g/mu l). This study is the first in vivo evidence showing the release of GABA produced by AMPH through a high affinity transporter mechanism. (C) 1998 Elsevier Science Ltd. All rights reser ved.