m-Octopamine: Normal Occurrence with p-Octopamine in Mammalian Sympathetic Nerves |
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Authors: | K. E. Ibrahim M. W. Couch C. M. Williams M. J. Fregly J. M. Midgley |
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Affiliation: | Veterans Administration Medical Center and Departments of Radiology, Gainesville, Florida, U.S.A.;Departments of Physiology, University of Florida College of Medicine, Gainesville, Florida, U.S.A.;Department of Pharmaceutical Chemistry, University of Strathclyde, Glasgow, Scotland |
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Abstract: | The development of a radiochemical enzyme assay for p-octopamine in 1969 led to its identification in a large number of invertebrate nerve systems and in mammalian sympathetic nerves. The original method by which p-octopamine was measured has now been found to be nonspecific; however, modifications of this procedure can determine both m- and p-octopamine. We recently developed a new specific method for the unequivocal identification and quantitative determination in tissue of the six octopamine and synephrine isomers. With this method--negative chemical ionization gas chromatography-mass spectrometry--the more physiologically active m-octopamine has been 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 to 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. |
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Keywords: | m-Octopamine p-Octopamine Mammalian sympathetic nerves Gas chromatography-mass spectrometry |
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