CART peptides are endogenous neurotransmitters that are involved in a variety of physiologic functions. Injection of CART 55-102 into the nucleus accumbens produces no effect, but when co-administered with cocaine, it reduces the locomotor and rewarding properties of cocaine. In a human study, subjects carrying a missense mutation of the CART gene exhibited increased anxiety and depression. Also, several animal studies support the idea that CART is involved in anxiety and depression, and they also suggest several possible mechanisms by which this may occur. Thus, there is interesting evidence that CART peptides play a role in anxiety and depression, and that CART peptides may be endogenous antidepressants.