Summary
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1.
Tracheal segments from guinea-pigs pretreated with 6-hydroxydopamine were incubated in isoprenaline at 37°C for 5 min in the absence or presence of phentolamine. Catechol-O-methyl transferase was inhibited by 100 μmol l−1 U-0521. Tissues were prepared for fluorescence histochemistry and accumulated isoprenaline in trachealis smooth muscle cells (fluorescence) was measured by microphotometry.
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2.
Phentolamine, in concentrations up to 100 μmol l−1, had no effect on isoprenaline fluorescence.
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3.
It is concluded that phentolamine does not inhibit extraneuronal uptake in concentrations used to block α-adrenoceptors in isolated tissue experiments. Thus, it can be present in experiments designed to examine the effects of extraneuronal uptake inhibitor drugs on β-adrenoceptormediated responses.
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References
Bönisch H, Uhlig W, Trendelenburg U (1974) Analysis of the compartments involved in the extraneuronal storage and metabolism of isoprenaline in the perfused heart. Naunyn-Schmiedeberg's Arch Pharmacol 283:223–244
Bryan LJ, O'Donnell SR (1980) Affinities of catecholamines for extraneuronal uptake in smooth muscle cells in trachealis muscle of guinea-pig. Naunyn-Schmiedeberg's Arch Pharmacol 311:139–146
Bryan LJ, O'Donnell SR (1981) Kinetic analyses of the mechanisms of action of inhibitors of the extraneuronal uptake of adrenaline in smooth muscle cells of guinea-pig trachea. Naunyn-Schmiedeberg's Arch Pharmacol 315:249–254
Cole JJ, O'Donnell SR (1981) Is phentolamine an inhibitor of extraneuronal uptake? Proc Austr Physiol Pharmacol Soc 12:146P
Cole JJ, O'Donnell SR, Wanstall JC (1982) β-Adrenoceptors and extraneuronal uptake in cat trachea. Br J Pharmacol 75, 22P
Ebner F (1981) The positive inotropic effect of (−)-noradrenaline and (±)-isoprenaline after chemical sympathectomy: evidence in favour of differences at a postsynaptic site. Naunyn-Schmiedeberg's Arch Pharmacol 316:8–18
Eisenfeld AJ, Axelrod J, Krakoff L (1967) Inhibition of the extraneuronal accumulation and metabolism of norepinephrine by adrenergic blocking agents. J Pharmacol Exp Ther 156:107–113
Foster RW (1967) The potentiation of the responses to noradrenaline and isoprenaline of the guinea pig isolated tracheal chain preparation by desipramine, cocaine, phentolamine, phenoxybenzamine, guanethidine, metanephrine and cooling. Br J Pharmacol 31:466–482
Foster RW (1969) An uptake of radioactivity from (±)-3H-isoprenaline and its inhibition by drugs which potentiate the responses to (−)-isoprenaline in the guinea-pig isolated trachea. Br J Pharmacol 35:418–427
Furchgott RF (1972) The classification of adrenoceptors (adrenergic receptors). An evaluation from the standpoint of receptor theory. In: Blaschko H, Muscholl E (eds) Handbook of Experimental Pharmacology, vol 33. Catecholamines. Springer, Berlin Heidelberg New York, pp 283–335
Garland LG, Marrion NV, Martin GR (1981) The extraneuronal O-methylation of 3H-(±)isoprenaline by guinea pig-tracheal rings in vitro. Naunyn-Schmiedeberg's Arch Pharmacol 318:88–93
Kenakin TP (1980) Errors in the measurement of agonist potency-ratios produced by uptake processes: a general model applied to β-adrenoceptor agonists. Br J Pharmacol 71:407–417
O'Donnell SR, Saar N (1973) A histochemical study of extraneuronal accumulation of noradrenaline in the guinea-pig trachea. Br J Pharmacol 49:267–278
Starke K, Montel H, Wagner T (1971) Effect of phentolamine on noradrenaline uptake and release. Naunyn-Schmiedeberg's Arch Pharmacol 271:181–192
Tanaka T, Starke K (1979) Binding of 3H-clonidine to an α-adrenoceptor in membranes of guinea-pig ileum. Naunyn-Schmiedeberg's Arch Pharmacol 309:207–215
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This study was supported by the National Health and Medical Research Council of Australia
These results were presented to the Australian Physiological and Pharmacological Society (Cole and O'Donnell 1981)
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Cole, J.J., O'Donnell, S.R. Evidence that phentolamine is not an inhibitor of extraneuronal uptake. Naunyn-Schmiedeberg's Arch. Pharmacol. 320, 221–223 (1982). https://doi.org/10.1007/BF00510131
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DOI: https://doi.org/10.1007/BF00510131