Mechanical and Chemical Factors Required for Maintaining Cardiac Rhythm in Drosophila melanogaster Larva

Background and Objective: Cardiac-intrinsic mechanisms for regulating heart rate (HR) in response to stretch have been characterized in many different organisms but the molecular mechanisms for mechanosensitive regulation are not yet fully understood. Drosophila melanogaster larva, with its simple and genetically tractable circulatory system, is well-suited to investigate the functional role of stretch-activated channels (SACs) and chemical modulators in regulating heart rate. Materials and Methods: Here we establish an exposed heart preparation that delivers continuous mechanical stimulation in the presence of pharmacological manipulations. Results: Continuous mechanical stimulation substantially stabilized HR over 2 h incubations compared to stagnant incubations with the same saline. The addition of a chemical modulator cocktail further enhanced HR stability in perfused preparations. To determine the role of mechanosensitive regulation in prolonged HR stability we assayed various pharmacological SAC blockers, e.g., amiloride, gadolinium, ruthenium red, streptomycin and tarantula toxin. Conclusion: The relative efficacy of these blockers on mechanically stabilized HR further establishes Drosophila larva as an appropriate system for investigating cardiac mechanosensation and provides novel insight into the underlying SACs.