On the identification of octopamine in mammals.

Many of the phenolic acids in human urine have been characterized, and several have been tentatively identified by means of their behavior on paper chromatograms (3). Further studies have revealed that most of them originate from dietary precursors, but a few have been found to be excreted always and in amounts which are relatively constant for a given individual despite marked changes in the diet. Among these are 4-hydroxy3-methoxymandelic acid, homovanillic acid, 5-hydroxyindoleacetic acid, and another acid which was identified tentatively as p-hydroxymandelic acid (3). The first three acids cited are known to be metabolites of the catecholamines and of serotonin, and monoamine oxidase is known to be involved in their metabolism.l By analogy, it seemed likely that p-hydroxymandelic acid might be a metabolite of the corresponding amine, p-hydroxymandelamine. The occurrence of this amine in nature was reported in 1952 by Erspamer (4), who identified it in extracts of salivary glands of the octopus and named it octopamine. Erspamer and his colleagues were not able to detect octopamine in other tissues of the octopus or in extracts from the tissues of vertebrates or invertebrates (5). With the use of ion exchange resins to separate selectively and to concentrate very small amounts of amines for two-dimensional paper chromatography, and with the use of inhibitors of monoamine oxidase to prevent the destruction of octopamine, it has been possible to demonstrate its presence in various tissues of the rabbit. In addition, it has been found to occur in the urine of humans, rats, and rabbits treated with monoamine oxidase inhibitors, and in very much smaller amounts in their normal urine. The large proportionate increase in octopamine in animals treated with monoamine oxidase inhibitors is suggestive that octopamine may be an important amine for consideration in studies on the therapeutic effects of the inhibitors.