Influence of caffeine and other methylxanthines on mechanical properties of isolated mammalian heart muscle. Evidence for a dual mechanism of action.

Action Potentials Adrenergic beta-Antagonists/pharmacology Animals Atropine/pharmacology Caffeine/antagonists & inhibitors,pharmacology Calcium/antagonists & inhibitors,pharmacology Calcium Isotopes Cats Electric Stimulation Heart/drug effects In Vitro Techniques Isoproterenol/pharmacology Muscle Contraction/drug effects Norepinephrine/antagonists & inhibitors Papillary Muscles/drug effects,physiology Procaine/pharmacology Propranolol/pharmacology Reserpine/pharmacology Strontium/pharmacology Strontium Isotopes Theobromine/pharmacology Theophylline/pharmacology Time Factors

Adrenergic beta-Antagonists Calcium Isotopes Strontium Isotopes Caffeine Procaine Atropine Reserpine Propranolol Theophylline Isoproterenol Theobromine Calcium Norepinephrine Strontium