Figure 2.

Intracellularly recorded photoreceptor responses of ina mutants and wild type. Photoreceptor responses to 20-s white stimuli recorded intracellularly from flies of the indicated genotypes are presented superposed on each other. In wild type, the response rapidly declines to a steady-state level (filled arrowhead), which depends on the intensity of the light stimulus, and remains there for the rest of the stimulus. This is a well-known adaptation response of photoreceptor to the light. In the ina mutants, on the other hand, the decline in amplitude (inactivation) that began at the onset of stimulus continues throughout the stimulus with the time course and the extent of decay depending on the mutant. The kinetics of decay can be complex in some mutants (inaC). Thus, the ina photoreceptor responses tend to terminate prematurely. The premature termination phenotype of a strong ina mutant, such as inaF^P106x, closely resembles that of null trp (transient receptor potential) mutants.