m‐Octopamine: Normal Occurrence with p‐Octopamine in Mammalian Sympathetic Nerves

Publisher Website
Google Scholar
Abstract
The development of a radiochemical enzyme assay for p-octopamine in 1969 led to its identification in a large number of invertebrate nerve system and in mammalian sympathetic nerves. The orginal method by which p-octopamine was measured is nonspecific; modifications of this procedure can determine both M- and p-octopamine. A new specific method was developed for the unequivocal identification and quantiative determination in tissue of the 6 octopamine and synephrine isomers. With this method, negative chemical ionization gas chromatography-mass spectrometry the more physiologically active m-octopamine was found in association with p-octopamine in 10 organs of the rat. m-Octopamine is present in concentrations equal to those of p-octopamine in heart, spleen and liver and in concentrations from 30-60% of p-octopamine in adrenals, vas deferens, brain, kidney, large intestine, bladder and lungs. In vivo inhibition of monoamine oxidase markedly increased the concentrations of both m- and p-octopamine in all organs examined. Both amines were virtually absent from all organs except the adrenals following chemical sympathectomy with 6-hydroxydopamine, thereby establishing that m- and p-octopamine are localized within sympathetic nerve endings.