“Blockade … Cd2+ (greater than 0.01 mM), nifedipine (greater than 3 microM), verapamil (greater …) and TMB-8 (greater than 10 microM) reduced the tension evoked by potassium somewhat more than it reduced the contractions induced by NA, while … seen in the presence of Ni2+ (greater than 0.1 mM).”