Odor suppression of voltage-gated currents contributes to the odor-inducedresponse in olfactory neurons

Olfactory chemotransduction involves a signaling cascade. In addition to tr iggering transduction, odors suppress ion conductances. By stimulating with brief odorant pulses, we observed a current associated with odor-induced s uppression of voltage-gated conductances and studied its time dependence. W e characterized this suppression current in isolated Caudiverbera caudiverb era olfactory neurons. All four voltage-gated currents are suppressed by od or pulses in almost every neuron, and suppression is caused by odors induci ng excitation and by those inducing inhibition, indicating a nonselective p henomenon, in contrast to transduction. Suppression has a 10-fold shorter l atency than transduction. Suppression was more pronounced when odors were a pplied to the soma than to the cilia, opposite to transduction. Suppression was also present in rat olfactory neurons. Furthermore, we could induce it in Drosophila photoreceptor cells, demonstrating its independence from the chemotransduction cascade. We show that odor concentrations causing suppre ssion are similar to those triggering chemotransduction and that both suppr ession and transduction contribute to the odor response in isolated olfacto ry neurons. Furthermore, suppression affects spiking, implying a possible p hysiological role in olfaction.