Neurotransmitters are natural messengers in the nervous system that send signals from one nerve cell across a synapse to another nerve cell or target organ. Serotonin plays a role in sleep, mood, intestinal function, pain control, and inflammation. Dopamine plays a role in cognitive function, memory, learning, and pleasure. In our bodies, dopamine is released as a result of rewarding experiences. Certain nutrients and amino acids may help to balance levels of neurotransmitters by providing co-factors that assist in the body?s ability to manufacture neurotransmitters.