Myocardial Contraction 36 heart atrium heart 34 Male 28 Animal 24 Rats 24 rat 24 animal experiment 20 heart muscle contractility 20 In Vitro 18 Support, Non-U.S. Gov't 18 animal cell 18 in vitro study 18 inotropism 18 nonhuman 18 Heart Atrium 16 propranolol 16 acetylsalicylic acid 14 indometacin 14 Animals 12 Mice 12 Mice, Inbred BALB C 12 Propranolol 12 drug efficacy 12 mouse 12 noradrenalin 12 Heart Rate 10 Ouabain 10 Rats, Inbred Strains 10 article 10