The enormous information handling capacity of nervous systems depends on the proper function of a rich variety of neurons and other excitable cells that display distinctive signal processing characteristics. This physiological complexity reflects cellular differences in the expression and regulation of ion channels. Genetic dissection has been successfully applied in elucidation of mechanisms underlying many biological processes in model systems. Drosophila has been a favored organism for such an approach to complex problems in higher organisms, such as function and development of the nervous system (Benzer, 1973; Pak and Pinto, 1976).