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.