Summary
Tritiated prazosin was used to characterize high affinity binding sites with characteristics similar to α 1 adrenoceptors in rat brain membranes. These sites were compared with α 2 adrenoceptors labeled with tritiated clonidine. The prazosin sites had an association constant of 2 nM−1 and bound the ligand optimal around pH 7.0. The density of the sites was 300 fmoles per mg of protein; the half time of dissociation of prazosin was 7 min at 30° C. The order or potencies of agonists, determined from binding-inhibition experiments with labeled prazosin, was: naphazoline > clonidine > adrenaline > noradrenaline > phenylephrine > α-methylnoradrenaline > dophamine. The order of potencies of antagonists was: prazosin > phenoxybenzamine > phentolamine > clozapine > yohimbine. Sodium ions and divalent cations as well as guanyl nucleotides have little or no effect on the binding of the labeled antagonist. This is in contrast to the binding of the labeled agonist clonidine (Glossmann and Presek, 1979a, 1979b). Labeled prazosin may be a useful tool to characterize α 1 adrenoceptors.
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This is part of the thesis of R. H. to be presented to the Fachbereich Humanmedizin, Justus Liebig-Universität Giessen, in partial fulfillment of the requirements for a Doctor of Medical Science degreee
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Hornung, R., Presek, P. & Glossmann, H. Alpha adrenoceptors in rat brain: Direct identification with prazosin. Naunyn-Schmiedeberg's Arch. Pharmacol. 308, 223–230 (1979). https://doi.org/10.1007/BF00501386
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DOI: https://doi.org/10.1007/BF00501386