Chapter 2 – Neural Circuits Underlying Escape Behavior in Drosophila: Focus on Electrical Signaling

Escape behaviors in invertebrates provide tractable systems for studying the neuronal basis of behavior, because these circuits comprise few relatively accessible cells. In Drosophila melanogaster, the Giant Fiber System (GFS) mediates rapid escape in response to visual and mechanosensory cues. When environmental threats are less pressing, a parallel, slightly slower but more directed, escape circuit is activated. The neural components of this alternative pathway have yet to be identified; by comparison, the GFS is well characterized. A forward genetic approach in the 1980s isolated mutants in which GF-evoked escape behavior is perturbed; analysis of one of these mutants, shakB, led to the discovery of the innexin family of gap-junction genes in the 1990s. shakB gene products are differentially expressed in the GFS neurons; the properties of the intercellular channels assembled from pre- and postsynaptically expressed proteins are consistent with the presence of rectifying and nonrectifying synapses in this escape circuit.