CONDITIONED INCREASES IN MESOLIMBIC DOPAMINE OVERFLOW BY STIMULI ASSOCIATED WITH COCAINE

Stimuli associated with cocaine come to acquire incentive-motivational as well as secondary reinforcing properties which can energize and ma intain behavior in laboratory animals as well as precipitate craving i n addicts. Environmental stimuli paired with a large dose of cocaine f or one training session elicited significant increases in locomotor ac tivity and in extracellular dopamine in the nucleus accumbens of rats during a second test session with a low dose of cocaine. The increases in extracellular dopamine are not likely a secondary consequence of t his increase in locomotor output of rats conditioned to cocaine, since doses of MK-801 which produced similar increases in locomotor behavio r had no effect on mesolimbic dopamine. These findings provide a neuro chemical mechanism for understanding the incentive motivational proper ties of stimuli associated with cocaine and may help to explain recidi vism of cocaine addicts when they return to an environment in which th e drug was used.