Normal: 116 mM NaCl 2.9 mM KCl 1.8 mM CaCl2 5.0 mM HEPES, pH 7.2.
High calcium: 116 mM NaCl 2.9 mM KCl 10 mM CaCl2 5 mM HEPES, pH 7.2.
Calcium free: 116 mM NaCl 2.9 mM KCl 5.0 mM HEPES, pH 7.2