An in vivo technique for pharmacological manipulation of Drosophila brain during optical recording

Drosophila melanogaster, an established model for genetic manipulation, has recently been used for studying olfactory perception, learning, and memory. Some of these important behavioral phenomena have been dissected with defined mutants, some to a single biochemical lesion, expressed in central brain structures known as the mushroom bodies. A previously introduced preparation used a window in the head capsule through which these structures could be imaged using genetically expressed fluorescent calcium sensors while applying physiological odorant stimuli. Unfortunately, technical constraints prevented direct manipulation of the mushroom bodies with this preparation. I describe here a preparation that will allow, for the first time, the direct pharmacological manipulation of these important structures during imaging in the living adult fly. Responses to discreet applications of acetylcholine were reversibly blocked with tubocurare and reversibly eliminated in calcium-free Ringers. This new technique will significantly enhance the usefulness of the Drosophila model system, allowing a more quantitative examination of the mechanisms involved in olfactory learning and memory.