Cocaine intake by rats correlates with cocaine-induced dopamine changes inthe nucleus accumbens shell

Extracellular dopamine levels were determined by microdialysis in the core and shell of the nucleus accumbens and the frontal cortex of rats before an d after an injection of cocaine (20 mg/kg, IP). After removal of the probes , these same animals were then tested for their voluntary intake of cocaine using the two-bottle, free-choice paradigm. Baseline dopamine levels and t heir responses to an injection of cocaine differed among the three brain ar eas. No significant correlations were found between baseline dopamine level s in any of the three brain regions and the voluntary cocaine consumption. A significant negative correlation was found between cocaine-induced increa ses in extracellular dopamine in the shell of the nucleus accumbens and the voluntary intake of cocaine (r = -0.73, p < 0.01). No such correlations we re observed in the accumbens core region or the frontal cortex. These resul ts provide further evidence of the role of the accumbal shell region in coc aine preference, and indicate that cocaine-induced increases in dopamine le vels play a role in oral cocaine self-administration or preference. In addi tion, this relatively novel approach in using the same animals for both coc aine induced neurotransmitter responses and cocaine preference studies can also be applied for the study of other neurotransmitters and drugs of abuse . (C) 2000 Elsevier Science Inc.