IN-VIVO MODULATION OF ACETYLCHOLINE IN THE NUCLEUS-ACCUMBENS OF FREELY MOVING RATS .2. INHIBITION BY GAMMA-AMINOBUTYRIC-ACID

OUT earlier studies suggest dopamine and serotonin interact with acety lcholine (ACh) in the nucleus accumbens (NAC) as part of a system for motivation and reinforcement. The purpose of the present experiment wa s to characterize a possible link between GABA and acetylcholine in th e nucleus accumbens using microdialysis in freely moving rats. Differe nt doses of GABA, muscimol, baclofen, saclofen and bicuculline were lo cally infused into the nucleus accumbens through the microdialysis pro be. GABA and its agonists dose-dependently decreased extracellular lev els of acetylcholine in the nucleus accumbens. In contrast the GABA(A) antagonist, bicuculline, dose-dependently increased extracellular ACh while the GABA(B) antagonist, saclofen, was without effect. Co-infusi on of bicuculline or saclofen was shown to block the decrease in recov erable ACh produced by muscimol or baclofen, respectively. The results demonstrate an inhibitory action of GABA on acetylcholine interneuron es in the nucleus accumbens involving both GABA(A) and GABA(B) recepto r subtypes. In addition a tonic inhibitory GABAergic tone is probably mediated through GABA(A) receptors.