A fairly consistent relationship has been observed between the effects of drugs on norepinephrine metabolism in animals and the known effects of these drugs on mood in man. Data are presented suggesting that stimulants or antidepressants may increase norepinephrine at adrenergic receptors in brain whereas lithium salts, which are effective in the treatment of manic and hypomanic states, may decrease norepinephrine at receptor sites. These findings are compatible with the hypothesis that some, if not all, depressions may be associated with a relative deficiency of norepinephrine at receptor sites in the brain while elations may be associated with an excess of this amine.Abstract Teaser