Intra-accumbal injection of CART (cocaine-amphetamine regulated transcript) peptide reduces cocaine-induced locomotor activity

Evidence suggests that CART (cocaine-amphetamine regu-lated transcript) peptides are mediators or modulators of the actions of psychostimulant drugs. In this study, the effects of intra-accumbal injections of rat long form (rl) CART 55-102 were examined. Injection of the peptide alone had no effect, but pretreatment with the peptide blunted or reduced the locomo-tor-inducing effects of cocaine after an i.p. injection. This effect was dose related and time limited, as expected. rlCART 1-27, a CART peptide fragment not active in other studies, was without effect on cocaine-induced locomotor activity. Because the ac-tions of cocaine involve dopamine, the effect of rlCART 55-102 on dopamine-induced locomotor activity was examined. Intra-accumbal injection of dopamine produced a dose-related and time-limited increase in locomotor activity, as expected. Coin-jection of rlCART 55-102 with dopamine blunted the effect. In summary, these data suggest that CART peptides in the nu-cleus accumbens would tend to oppose the actions of cocaine. Cocaine- and amphetamine-regulated transcript (CART) peptides are neurotransmitters that appear to be involved in feeding and satiety, stress, endocrine control, sensory pro-cessing, autonomic control, and other functions (Thim et al., 1998a; Adams et al., 1999; Couceyro and Lambert, 1999