Muscarinic receptor binding in the mouse heart: the selective modulatory effect of fluoride ion on agonist binding

The effect of fluoride ion on the binding of the specific muscarinic agonist ligand [3H]cis methyldioxolane ([3H]CD) to the mouse cardiac muscarinic receptor was investigated. Utilizing equilibrium ligand binding experiments, sodium fluoride (10mM) was shown to decrease [3H]CD binding, measured at a concentration of 2 nM, by 52%. Studies with several different ions demonstrated that the reduction in [3H]CD binding was a specific effect of fluoride. This fluoride modulation was selective for agonist binding, as no effect of fluoride on the binding of the muscarinic antagonist [3H](-) quinuclidinyl benzilate (QNB) was observed.