Evidence for the presence of m-tyramine, p-tyramine, tryptamine, and phenylethylamine in the rat brain and several areas of the human brain.

Postmortem human brains have been obtained from four nonpsychiatric patients, aged 59-70 years. Regional analysis of the trace amines phenylethylamine, p-tyramine, m-tyramine, and tryptamine has indicated that the amines are distributed heterogeneously throughout the brain, but are most concentrated in the basal ganglia. Although the levels are very low, evidence obtained from animal studies has indicated that the trace amines have a very rapid turnover rate. Their presence in a brain synaptosomal fraction suggests a possible involvement in the process of neurotransmission. Postmortem changes in human brain amines are discussed in relation to those occurring postmortem in the rat brain, in which phenylethylamine, p-tyramine, and tryptamine have been shown to increase to levels greater than those prevailing in vivo.