Summary
We used novel highly subtype-selective antagonists to study whether α1A- and/or α1B-adrenoceptors mediate the stimulation of inositol phosphate generation by noradrenaline in rat cerebral cortex. Phentolamine (10 μM) and prazosin (100 nM) completely abolished the stimulated inositol phosphate generation. The α1A-selective antagonists 5-methyl-urapidil (100 nM) and (+)− and (−)-niguldipine (10 nM) caused only weak inhibition or none at all although these concentrations occupied α1A-adrenoceptors almost completely. In contrast, pretreatment with the irreversible α1B-selective chloroethylclonidine reduced the noradrenaline-stimulated inositol phosphate generation by 76 ± 8%. These data demonstrate that α1B-adrenoceptors couple to inositol phosphate generation; the signal transduction system of α1A-adrenoceptors remains unclear.
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Michel, M.C., Hanft, G. & Gross, G. α1B- but not α1A-adrenoceptors mediate inositol phosphate generation. Naunyn-Schmiedeberg's Arch Pharmacol 341, 385–387 (1990). https://doi.org/10.1007/BF00180666
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DOI: https://doi.org/10.1007/BF00180666