Neuropeptides
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CART (cocaine- and amphetamine-regulated transcript) peptides appear to be mediators or modulators of psychostimulant drugs. An interesting result in the nucleus accumbens has been that injection of CART peptide has no effect by itself on locomotor activity, but it reduces the locomotor activity induced by cocaine or amphetamine. However, in the ventral tegmental area (VTA), injections of CART peptide have been shown to increase locomotor activity, although to a lesser degree [Kimmel, H. ⋯ CART reduced the locomotor activating effects of systemic cocaine, especially at higher doses of CART. These results imply that intra-VTA CART is not simply acting in the same manner as cocaine, and is likely to oppose the action of cocaine. This has implications for the physiological significance of CART-DA (dopamine) interactions and for medications development.