Modulation of sensory-CNS-motor circuits by serotonin, octopamine, and dopamine in semi-intact Drosophila larva

We have introduced an in-situ preparation to induce motor unit activity by stimulating a sensory-CNS circuit, using the third instar larvae of Drosophila melanogaster. Discrete identifiable motor units that are well defined in anatomic and physiologic function can be recruited selectively and driven depending on the sensory stimulus intensity, duration, and frequency. Since the peripheral nervous system is bilaterally symmetric to coordinate bilateral symmetric segmental musculature patterns, fictive forms of locomotion are able to be induced. Monitoring the excitatory postsynaptic potentials (EPSP) on the prominent ventral longitudinal body wall muscles, such as m6 and m12, provides additional insight into how the selective motor units might be recruited within intact animals. We also introduce the actions of the neuromodulators (serotonin, octopamine (OA) and dopamine (DA)) on the inducible patterns of activity within the sensory-motor circuit. The powerful genetic manipulation in Drosophila opens many avenues for further investigations into the circuitry and cellular aspects of pattern generation and developmental issues of circuitry formation and maintenance in the model organism.