Article date: February 1980
By: H. MAJEWSKI, M.W. McCULLOCH, M.J. RAND, D.F. STORY in Volume 71, Issue 2, pages 435-444
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.
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.
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.
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.
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.
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.
DOI: 10.1111/j.1476-5381.1980.tb10956.x
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