Chronic cocaine alters limbic extracellular dopamine. Neurochemical basis for addiction.

The extracellular concentration of dopamine in the ventral striatum was measured daily by means of brain microdialysis. Chronic cocaine (10 mg/kg twice daily) altered the dopamine output compared to that in vehicle-injected rats, inducing a pronounced increase in the first 3 days followed by a clear-cut decrease. This reduction in the output of dopamine during chronic cocaine as well as during withdrawal may be neurochemical substrate for the addictive properties of cocaine.