The inositol 1, 4, 5-trisphosphate receptor is required for maintenance of olfactory adaptation in Drosophila antennae

Abstract

A role for inositol 1,4,5-trisphosphate (IP₃) as a second messenger during olfactory transduction has been postulated in both vertebrates and invertebrates. However, given the absence of either suitable pharmacological reagents or mutant alleles specific for the IP₃ signaling pathway, an unequivocal demonstration of IP₃ function in olfaction has not been possible. Here we have investigated the role of a well-established cellular target of IP₃-the IP₃ receptor (IP₃R)-in olfactory transduction in Drosophila. For this purpose we tested existing viable combinations of IP₃R mutant alleles, as well as a newly generated set of viable itpr alleles, for olfactory function. In all of the viable allelic combinations primary olfactory responses were found to be normal. However, a subset of itpr alleles (including a null allele) exhibit faster recovery after a strong pulse of odor, indicating that the IP₃R is required for maintenance of olfactory adaptation. Interestingly, this defect in adaptation is dominant for two of the alleles tested, suggesting that the mechanism of adaptation is sensitive to levels of the IP₃R.