ADRENALINE ACTIVATION OF PREJUNCTIONAL β‐ADRENOCEPTORS IN GUINEA‐PIG ATRIA
Open Access
- 1 February 1980
- journal article
- Published by Wiley in British Journal of Pharmacology
- Vol. 71 (2), 435-444
- https://doi.org/10.1111/j.1476-5381.1980.tb10956.x
Abstract
1 Adrenaline in a concentration of 1.0 μm depressed the stimulation-induced efflux of tritium from the guinea-pig atria incubated with [3H]-noradrenaline, whereas adrenaline in a concentration of 0.5 nm significantly enhanced the stimulation-induced efflux of tritium. This enhancement was blocked by metoprolol (0.1 μm) and thus appears to be mediated by β-adrenoceptors. 2 In guinea-pig atria incubated with unlabelled adrenaline and then with [3H]-noradrenaline, both catecholamines were released by field stimulation. In such atria metoprolol, practolol, oxprenolol or propranolol decreased the stimulation-induced efflux of tritium. These effects did not occur if the atria were incubated with unlabelled noradrenaline and then with [3H]-noradrenaline, suggesting that neuronally released adrenaline activates prejunctional β-adrenoceptors. 3 The effect of oxprenolol in decreasing the release of tritium from guinea-pig atria, incubated with unlabelled adrenaline and then with [3H]-noradrenaline was greater in the presence of phentolamine. This may reflect the α-adrenoceptor blocking activity of oxprenolol.Keywords
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