Odorants suppress a voltage-activated K+ conductance in rat olfactory neurons

Odorants suppress a voltage-activated K+ conductance in rat olfactory neuro ns. J. Neurophysiol. 82: 226-236, 1999. Stimulation of olfactory receptor n eurons (ORNs) with odors elicits an increase in the concentration of cAMP l eading to opening of cyclic nucleotide-gated (CNG) channels and subsequent depolarization. Although opening of CNG channels is thought to be the main mechanism mediating signal transduction. modulation of other ion conductanc es by odorants has been postulated. To determine whether K+ conductances ar e modulated by odorants in mammalian ORNs, we examined the response of rat ORNs to odors by recording membrane current under perforated-patch conditio ns. We find that rat ORNs display two predominant types of responses. Thirt y percent of the cells responded to odorants with activation of a CNG condu ctance. In contrast, in 55% of the ORNs, stimulation with odorants inhibite d a voltage-activated K+ conductance (I-KO). Ln terms of pharmacology, ion permeation, outward rectification, and time course for inactivation, I-KO r esembled a delayed rectifier K+ conductance. The effect of odorants on I-KO was specific (only certain odorants inhibited I-KO in each ORN) and concen tration dependent, and there was a significant latency between arrival of o dorants to the cell and the onset of suppression. These results indicate th at indirect suppression of a K+ conductance (I-KO) by odorants plays a role in signal transduction in mammalian ORNs.