Direct inotropic effect of the beta-2 receptor agonist terbutaline on impaired diaphragmatic contractility in septic rats

The purpose of this study was to determine which beta-adrenoceptor agonist (1 or 2) is responsible for the direct inotropic effects on diaphragmatic contractility during sepsis. Rats were divided into two groups: a cecal ligation and perforation (CLP) group and a sham group. The hemidiaphragm was removed at 16 hours after the operation. Dobutamine (a beta-1 agonist) or terbutaline (a beta-2 agonist) was administered to an organ bath containing diaphragmatic tissues, and muscle contractility was assessed. Muscle contractility was diminished in the CLP group. Terbutaline increased peak twitch tension, caused an upward shift in the force-frequency curves, and improved contractility of the fatigued diaphragm in the CLP group. Dobutamine did not have any effect on these parameters in the CLP group. We conclude that activation of beta-2 adrenoceptors might be responsible for the direct inotropic effects on the diaphragm in an intra-abdominal septic model.