THE K-GO IS REQUIRED FOR THE TRANSDUCTION OF A SUBSET OF ODORANTS IN ADULT DROSOPHILA-MELANOGASTER( CHANNEL GENE ETHER A GO)

The functional identity of an olfactory receptor neuron is determined in part by its repertoire of responses to odorants. As an approach tow ard understanding the contributions of particular conductances to olfa ctory neuron excitability and odor discrimination, we have investigate d the role of the putative cyclic nucleotide-modulated K+ channel subu nit encoded by the ether a go-go (eag) gene in odorant responsiveness in Drosophila melanogaster. Four independent mutant eag alleles exhibi ted reduced antennal sensitivity to a subset of nine odorants, ail hav ing short aliphatic side chains: ethyl butyrate (EB), propionic acid, 2-butanone, and ethyl acetate. Significantly fewer eag antennal neuron s responded to EB compared with control neurons; the proportion sensit ive to 2-heptanone was similar to controls. Two aspects of the charact er of EB-induced excitability were affected by mutations in eag. First , fewer EB-induced inhibitory responses were observed in eag mutants, and second, fewer excitatory odorant responses dependent on extracellu lar Ca2+ were observed. Furthermore, modulation of neuronal excitabili ty by membrane-permeant cyclic nucleotide analogs was largely eag depe ndent. Focal application of high K+ saline to sensillae altered the ex citability of the majority of neurons from wild-type but not eag anten nae, suggesting that Fag may have a dendritic localization.