The presence and characterization of Force Depression in the Drosophila jump muscle

Force Depression (FD) describes the decrease in steady-state force production after active shortening in skeletal muscle. Despite being well characterized in skeletal muscle, the underlying mechanism remains unknown. The Drosophila jump muscle, tergal depressor of the trochanter (TDT), has recently been demonstrated to be mechanically similar to mammalian skeletal muscle, and due to the genetic simplicity of the organism, the TDT proves to be an excellent model to study FD. This investigation aimed to demonstrate both the presence of FD in the TDT, and that the phenomenon presented characteristically similar to skeletal muscle. In order to achieve this, wild-type Drosophila TDTs (n=10) were examined for FD in response to shortening amplitude (5, 10, 20% ML) and rate (4, 20, 200% ML/s). Results indicate that similar to mammalian skeletal muscle, TDTs exhibited an increase in the amount of FD with increasing amplitudes and decreasing rates of shortening.