CART peptides (CART 55–102 and CART 62–102) are neurotransmitters and endocrine factors in the nervous system and periphery.  They have been implicated in the regulation of feeding and body weight, drug reward and reinforcement and other processes. They also have neuro-protective properties and promote the survival and differentiation of neurons in vitro.  CART peptides appear early in the development of the CNS and other tissues suggesting a role in the development of specific regions of the brain.  GI-tract, pancreas and ovary. While the importance of CART peptides is clear, little is known about the cellular mechanisms by which CART peptides exert their effects.

CART peptides have a role in drug abuse by virtue of the fact that they are modulators of mesolimbic function. Key findings supporting a role in drug abuse are as follows. First, high densities of CART-containing nerve terminals are localized in mesolimbic areas. Second, CART 55 to 102 blunts some of the behavioral effects of cocaine and dopamine (DA). This functional antagonism suggests that CART peptides be considered as targets for medications development. Third, CREB in the nucleus accumbens has been shown to have an opposing effect on cocaine self-administration. CREB may activate CART expression in that region, and, if so, CART may mediate at least some of the effects of CREB. Fourth, in addition to the effects of CART on DA, DA can influence CART in the accumbens. Thus a complex interacting circuitry likely exists. Fifth, in humans, CART is altered in the ventral tegmental area of cocaine overdose victims, and a mutation in the CART gene associates with alcoholism.

No receptor for CART peptide has yet been identified, but some cellular effects have been observed, notably modulation of voltage-gated calcium signaling.  Also, injection of CART 55–102 into the lateral ventricles has been found to cause an increase in c-Fos levels in a variety of neurons.  In an effort to elucidate further the cellular signaling effects of CART peptides, and because of the observed effects of CART peptide on differentiation and development.