The following hypotheses are suggested concerning the possible roles of sympathomimetic amines in psychiatric conditions:1. Isuprel, or a similar substance, may be an important chemical mediator in anxiety.2. Another amine, possibly nor-epinephrine, may be an important chemical mediator in aggression and hostility.3. When a patient experiences approximately equal quantities of hostility and anxiety, equipotent concentrations of Isuprel and the other amine may be liberated, producing depression, by a mechanism similar to that whereby a mixture of 2 amines depresses the isolated mammalian auricle, although either amine alone has a stimulant action.An additional possibility suggested by continuing studies in this field is that the depression of rate and force observed with the mixture of amines is produced by an intermediate metabolite, formed within 1 or 2 minutes.Abstract Teaser