Article date: February 1984
By: Fola M. Tayo in Volume 81, Issue 2, pages 289-291
The effect of noradrenaline and isoprenaline were studied in the 15‐day old chick atria. Noradrenaline increased both the rate and force of atrial contractions whilst isoprenaline only slightly increased force at very high concentrations.
The increase in force after noradrenaline and isoprenaline was reduced by phentolamine, an α‐adrenoceptor antagonist. The β‐antagonist, propranolol and the cardioselective β1‐adrenoceptor antagonist, atenolol, did not reduce the positive inotropy. Noradrenaline‐induced positive chronotropy was, however, resistant to both α‐ and β‐adrenoceptor blockade.
It is concluded that the force of contraction of the chick atria may be α‐adrenoceptor‐mediated whilst the rate seems to be mediated by a mechanism sensitive to noradrenaline but insensitive to α‐and β‐adrenoceptor blockade.
The effect of noradrenaline and isoprenaline were studied in the 15‐day old chick atria. Noradrenaline increased both the rate and force of atrial contractions whilst isoprenaline only slightly increased force at very high concentrations.
The increase in force after noradrenaline and isoprenaline was reduced by phentolamine, an α‐adrenoceptor antagonist. The β‐antagonist, propranolol and the cardioselective β1‐adrenoceptor antagonist, atenolol, did not reduce the positive inotropy. Noradrenaline‐induced positive chronotropy was, however, resistant to both α‐ and β‐adrenoceptor blockade.
It is concluded that the force of contraction of the chick atria may be α‐adrenoceptor‐mediated whilst the rate seems to be mediated by a mechanism sensitive to noradrenaline but insensitive to α‐and β‐adrenoceptor blockade.
DOI: 10.1111/j.1476-5381.1984.tb10077.x
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