EFFECTS OF COCAINE AND AMPHETAMINE ON ACETYLCHOLINE-RELEASE IN THE HIPPOCAMPUS AND CAUDATE-NUCLEUS

The role of dopamine in the control of hippocampal acetylcholine relea se was evaluated by using in vivo microdialysis. The effects of the tw o psychostimulants, cocaine and d-amphetamine, were studied on acetylc holine release in the hippocampus and compared to effects observed in the caudate nucleus. Administration of cocaine (10 and 20 mg/kg i.p.) increased acetylcholine release by 130 and 190% in the hippocampus, wh ereas in the caudate nucleus the enhancement was 51 and 80% over basal values, respectively. After the injection of d-amphetamine (1 and 2 m g/kg i.p.) the enhancement of acetylcholine release was 1 10 and 210% in the hippocampus whereas it was 35 and 54%, respectively, in the cau date nucleus. As observed in the caudate nucleus, pretreatment with th e dopamine D1 receptor antagonist, SCH 23390, antagonized the cocaine- and amphetamine-induced increase in hippocampal acetylcholine release . These results show that cocaine and d-amphetamine, by increasing dop aminergic transmission, enhance the extracellular concentrations of ac etylcholine in both brain areas. The relative enhancement in the hippo campus was far greater than that in the caudate nucleus, suggesting th at dopaminergic control of cholinergic function differs in these two b rain areas. The results also suggest that endogenous dopamine, by faci litating the release of acetylcholine in the hippocampus, may particip ate in the regulation of hippocampal cognitive processes.