The gamma-aminobutyric acid-dopamine (GABA-DA) relationship was studied by intracerebral microdialysis in the prefrontal cortex. Nomifensine (5 microM) was included in the Ringer solution during all the dialysis experiments. Muscimol, a GABAA receptor agonist (50 and 500 microM) did not affect the extracellular output of DA and 3,4-dihydroxyphenylacetic acid (DOPAC). Baclofen, a GABAB receptor agonist (50 microM) significantly decreased the extracellular output of DA and DOPAC. On the other hand, picrotoxin and phaclofen, GABAA and GABAB receptor antagonists respectively, at a concentration of 50 microM, both significantly increased the release of DA. While the DOPAC level was affected only by picrotoxin perfusion. The present study indicates that GABA could control the release of DA in the prefrontal cortex.