title: On the importance of external calcium for sinus node automaticity in spontaneously beating guinea-pig atria.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006168:Guinea Pigs; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D012849:Sinoatrial Node / Q000187:drug effects*
chemical_list: D002118:Calcium