Force Depression in the Drosophila Jump Muscle

The depression of isometric force after active shortening, termed force depression (FD), is a well-accepted characteristic of skeletal muscle that has been demonstrated in both whole muscle [1,3] and single-fiber preparations [1,2]. Although this history-dependent behavior has been observed experimentally for over 70 years, its underlying mechanism(s) remain unknown. Drosophila melangastor, commonly known as the fruit fly, is a well established, comprehensively understood, and genetically manipulable animal model. Furthermore, Drosophila have proved to be an accurate model species for studying muscle mechanics, and the Tergal Depressor of the Trochanter (TDT), or jump muscle, has most precisely resembled the mechanics of mammalian skeletal muscle [4]. Due to the structural and phenomenological similarities of the TDT muscle to skeletal muscle, in addition to the potential use of genetic mutations in fly models, it is extremely advantageous to investigate the presence of history dependent phenomenon in the TDT. If such phenomena are present, further investigation utilizing different myosin and actin isoforms to study the underlying mechanism(s) could produce new insight into this history-dependent phenomenon, otherwise impossible to elucidate using current experimental models. Thus, it is the goal of this study to determine the presence and degree of FD in the TDT muscle of wild type Drosophila.