This chapter describes neurotransmitters in health and disease. Dopamine (DA) is a catecholamine consisting of a catechol-moiety attached to an ethylamine. Dopamine is related to Melanin, the dark colored pigment, formed from oxidation of dopamine/tyrosine/L-dopa, is present in skin as well as substantia nigra of brain. Dopamine being a polar molecule does not cross the blood-brain barrier (BBB). The three most important dopaminergic tracts are nigrostriatal tract, mesolimbic-mesocortical DA tract, and tuberoinfundibular tract. DA includes norepinephrine and epinephrine, serotonin, histamine, and acetylcholine.