Olfactory adaptation depends on the trp Ca2+ channel in Drosophila

Olfactory adaptation is shown to occur in Drosophila, at both behavioral an d physiological levels. In a behavioral paradigm, the extent of adaptation is shown to depend on the dose and duration of the adapting stimulus. Half- maximal adaptation occurred after 15 sec of exposure to an odor, and recove ry occurred with a half-time of 1.5 min, under a set of test conditions. Cr oss-adaptation was observed among all odor combinations tested, although to a lesser extent than when the same odor was used as both the adapting and the test stimulus. Mutants of the transient receptor potential (Trp) Ca2+ c hannel were normal in olfactory response, but defective in olfactory adapta tion, when measured either behaviorally or in tests of antennal physiology. These results indicate that olfactory response and adaptation can be disti nguished. Trp expression was detected in the developing antenna but, surpri singly, not in the mature antenna. These results, together with temperature -shift analysis of a temperature-sensitive trp mutant, provide evidence of a role of Trp in olfactory system development.