Amphetamine produces sensitized increases in locomotion and extracellular dopamine preferentially in the nucleus accumbens shell of rats administered repeated cocaine

Alterations in dopamine transmission in the nucleus accum-bens, which is composed of two anatomically distinct compart-ments termed the shell and core, contribute to the expression of cocaine-induced behavioral sensitization. To test potential presynaptic components of behavioral sensitization, the behav-ioral and neurochemical response to amphetamine administra-tion in the accumbens shell and core was measured at early (days 1-3) and late (days 20-22) withdrawal in rats pretreated with systemic cocaine (15 mg/kg x 2 days, 30 mg/kg x 5 days) or saline. Behavioral sensitization was observed at late, but not early withdrawal when amphetamine was microinjected into the nucleus accumbens shell of cocaine-pretreated rats. There were no significant differences between cocaine- and saline-pretreated animals when behavior was monitored after amphet