The Journal of Neurophysiology Vol. 82 No. 1 July 1999, pp. 226-236
Copyright ©1999 by the American Physiological Society

Odorants Suppress a Voltage-Activated K⁺ Conductance in Rat Olfactory Neurons

 ¹Monell Chemical Senses Center;  ²Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104; and  ³Department of Cellular and Structural Biology, University of Colorado Health Sciences Center, Denver, Colorado 80262

Lischka, Fritz W., John H. Teeter, and Diego Restrepo. Odorants Suppress a Voltage-Activated K⁺ Conductance in Rat Olfactory Neurons. J. Neurophysiol. 82: 226-236, 1999.Stimulation of olfactory receptor neurons (ORNs) with odors elicits an increase in the concentration of cAMP leading 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 conductances by odorants has been postulated. To determine whether K⁺ conductances are modulated by odorants in mammalian ORNs, we examined the response of rat ORNs to odors by recording membrane current under perforated-patch conditions. We find that rat ORNs display two predominant types of responses. Thirty percent of the cells responded to odorants with activation of a CNG conductance. In contrast, in 55% of the ORNs, stimulation with odorants inhibited a voltage-activated K⁺ conductance (I_Ko). In terms of pharmacology, ion permeation, outward rectification, and time course for inactivation, I_Ko resembled a delayed rectifier K⁺ conductance. The effect of odorants on I_Ko was specific (only certain odorants inhibited I_Ko in each ORN) and concentration dependent, and there was a significant latency between arrival of odorants to the cell and the onset of suppression. These results indicate that indirect suppression of a K⁺ conductance (I_Ko) by odorants plays a role in signal transduction in mammalian ORNs.