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

A role for inositol 1,4,5-trisphosphate (IP,) as a second messenger during olfactory transduction has been postulated in both vertebrates and inverteb rates.]However, given the absence of either suitable pharmacological reagen ts or mutant alleles specific for the IF, 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. Far this purp ose 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 fo und to be normal. However, a subset of itpr alleles (including a null allel e) exhibit faster recovery after a strong pulse of odor, indicating that th e IP3R is required for maintenance of olfactory adaptation. Interestingly, this defect in adaptation is dominant far two of the alleles tested, sugges ting that the mechanism of adaptation Is sensitive to levels of the IP3R. ( C) 2000 John Wiley & Sons. Inc.