RETRACTED ARTICLE: Dibutyryl cyclic AMP increases the contractility of fatigued diaphragm in dogs

The effects of dibutyryl cyclic AMP (DBcAMP) on the contractility of nonfatigued and fatigued diaphragms were studied in 36 anesthetized and mechanically ventilated dogs. The animals were divided into four groups. In group C1 (n=8), dogs without fatigue received only Ringer's lactate solution. In group D1 (n=8), dogs without fatigue were given a continuous infusion of DBcAMP 0.2 mg·kg(-1)·min(-1). In groups C2 and D2 (n=10 each), diaphragmatic fatigue was induced by intermittent supramaximal bilateral electrophrenic stimulation at a frequency of 20 Hz applied for 30 min. In group D2, after producing fatigue, DBcAMP 0.2 mg·kg(-1)·min(-1) was administered. In groups C2, only Ringer's solution was administered during this period. Diaphragmatic contractility was assessed by measuring the transdiaphragmatic pressure (Pdi, cmH2O). No difference in Pdi was observed in groups C1 and D1. After diaphragmatic fatigue in groups C2 and D2, Pdi at low-frequency (20-Hz) stimulation decreased significantly compared with the prefatigue values (group C2; 9.3±1.9vs 12.5±2.4, group D2; 9.3±2.1vs 12.5±2.6; mean±SD;P<0.05), whereas no change in Pdi was observed at high-frequency (100-Hz) stimulation. In group D2, Pdi at both stimuli increased significantly with an infusion of DBcAMP compared with the fatigue values (20 Hz; 13.3±3.3vs 9.3±2.1, 100 Hz; 23.4±3.6vs 21.3±3.2;P<0.05). In group C2, the speed of recovery from fatigue was relatively slower at 20-Hz stimulation than at 100-Hz stimulation. It is concluded that DBcAMP increases the contractility of fatigued diaphragm, but that this agent does not affect the contractility of nonfatigued diaphragm.