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J Pharm Pharmacol. 1987 Sep;39(9):752-4.

Beta-adrenergic activities of octopamine and synephrine stereoisomers on guinea-pig atria and trachea.

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Research Institute, May & Baker, Ltd., Dagenham, Essex, UK.


The activities of the (-)- and (+)-forms of m- and p-octopamine and m- and p-synephrine on beta 1- and beta 2-adrenoceptors in guinea-pig atria and trachea have been compared with that of noradrenaline. The rank order of potency of the (-)-forms on beta 1-adrenoceptors was noradrenaline greater than m-synephrine greater than m-octopamine = p-octopamine greater than p-synephrine. m-Synephrine was 100-fold, m- and p-octopamine about 6000-fold, and p-synephrine about 40,000-fold less active than noradrenaline. The (+)-forms were 1-2 orders of magnitude less active than their (-)-counterparts. The four (-)-compounds were more than four orders of magnitude less active than noradrenaline on beta 2-adrenoceptors, and the (+)-forms had no detectable activity in concentrations as high as 10(-4) M. If m- and p-octopamine are co-released with noradrenaline in amounts proportional to their concentration, their activities at these structures are too low to be physiologically significant.

[Indexed for MEDLINE]

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