title: Dual effects of fluoride on the action potential, contraction, and membrane currents in frog atrial muscle.
abstract: The effects of NaF (10(-7) - 10(-2) M) on the membrane potential, current, and contractile tension in bullfrog atrial muscle were investigated under voltage-clamped or unclamped conditions. NaF showed two opposite actions, positive and negative inotropic effects, depending on the concentration of the drug. NaF in lower concentrations produced a marked increase in contractility, a moderate prolongation of action potential, an augmentation of calcium response, and an increase of ICa-dependent tension. Contrarily, NaF in higher concentrations produced an inhibition of contractile tension associated with a shortening of action potential, an increase in potassium conductance, and an inhibition of calcium response. These results indicate that NaF affects the contractile response by dual mechanisms.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001001:Anura; D016275:Atrial Function; D002118:Calcium / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology*; D006325:Heart Atria / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D011892:Rana catesbeiana
chemical_list: D005459:Fluorides; D002118:Calcium