Sorota_1986_J.Pharmacol.Exp.Ther_236_602

Reference

Title : Comparison of muscarinic receptor properties in hatched chick heart atrium and ventricle - Sorota_1986_J.Pharmacol.Exp.Ther_236_602
Author(s) : Sorota S , Adam LP , Pappano AJ
Ref : Journal of Pharmacology & Experimental Therapeutics , 236 :602 , 1986
Abstract :

We have reported previously that chick myocardium responds to muscarinic agonists with a decrease in slow inward current in both atrial and ventricular muscle. A second ionic current, the background potassium current, is increased in the atrium but not in the ventricle. A possible explanation for the modulation of potassium current in atrium only is the existence of a unique muscarinic receptor population in atrium responsible for potassium conductance changes. We looked for differences in atrial and ventricular muscarinic receptors by pharmacological and biochemical techniques. The dissociation constants for binding of l-[3H]quinuclidinyl benzilate were 46 pM in both tissues. Estimates for binding of atropine in competitive binding experiments gave dissociation constants of 1.8 nM in atrium and 2.0 nM in ventricle. Pharmacologic evaluation of atropine occupancy of muscarinic receptor by Schild analysis showed no difference in the dissociation constants in atrium (1.7 nM) and ventricle (1.1 nM). Displacement of 0.1 nM [3H]quinuclidinyl benzilate with carbachol showed the atrium to have a higher apparent affinity for agonist than the ventricle (atrium IC50 = 8.2 X 10(-6) M, ventricle IC50 = 2.1 X 10(-5) M). Computerized curve fitting analysis detected three binding states (super high, high and low affinity) for carbachol in the atrium and ventricle in the absence and presence of 5'-guanylylimidodiphosphate (10(-4) M). We did not detect a qualitative difference between atrial and ventricular muscarinic receptors. Muscarinic-induced potassium conductance changes which occur in the atria do not appear to be due to a unique muscarinic receptor in atria.

PubMedSearch : Sorota_1986_J.Pharmacol.Exp.Ther_236_602
PubMedID: 3754007

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Citations formats

Sorota S, Adam LP, Pappano AJ (1986)
Comparison of muscarinic receptor properties in hatched chick heart atrium and ventricle
Journal of Pharmacology & Experimental Therapeutics 236 :602

Sorota S, Adam LP, Pappano AJ (1986)
Journal of Pharmacology & Experimental Therapeutics 236 :602