EXTRACELLULAR DOPAMINE, NOREPINEPHRINE, AND SEROTONIN IN THE VENTRAL TEGMENTAL AREA AND NUCLEUS-ACCUMBENS OF FREELY MOVING RATS DURING INTRACEREBRAL DIALYSIS FOLLOWING SYSTEMIC ADMINISTRATION OF COCAINE AND OTHER UPTAKE BLOCKERS

Extracellular levels of dopamine (DA), serotonin (5-HT), and norepinep hrine (NE) were measured by microdialysis in conscious rats equipped w ith dual probes, one in the ventral tegmental area (VTA) and another o ne in the contralateral nucleus accumbens (NACC). Dialysate content of all amines in both regions was essentially abolished by local infusio n of tetrodotoxin (1 mu M) or Ca2+-free buffer. Injection of the selec tive DA uptake blocker GBR 12935 (15 mg/kg IP) increased DA, as well a s NE and, to a lesser extent, 5-HT in the VTA; it increased DA more th an 5-HT in the NACC. The selective NE uptake blocker desipramine (10 m g/kg IP) increased NE but also 5-HT in the VTA and NACC; the DA level was persistently enhanced in the VTA, whereas in the NACC it initially rose and then fell below baseline value. The selective 5-HT uptake bl ocker citalopram (15 mg/kg IP) was generally more effective in elevati ng dialysate level of 5-HT than that of other amines in both regions. Cocaine (20 mg/kg IP) was non-selective in enhancing all three amines in both regions. There is considerable crosstalk between monoamine sys tems occurring upon systemic administration of uptake blockers, and th e VTA and NACC are notably different in the time course of the DA effe ct (long-lasting versus transient).