Related Experiment Videos
Odorants suppress a voltage-activated K+ conductance in rat olfactory neurons
F W Lischka1, J H Teeter, D Restrepo
1Monell Chemical Senses Center, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Abstract:
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 (IKo). In terms of pharmacology, ion permeation, outward rectification, and time course for inactivation, IKo resembled a delayed rectifier K+ conductance. The effect of odorants on IKo was specific (only certain odorants inhibited IKo 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 (IKo) by odorants plays a role in signal transduction in mammalian ORNs.
Insights
Odor stimulation in rat olfactory receptor neurons (ORNs) can activate cyclic nucleotide-gated (CNG) channels or inhibit a voltage-activated potassium current (IKo). This potassium channel modulation suggests a novel role for odorant-induced K+ conductance changes in olfactory signal transduction.
Area of Science:
- Neuroscience
- Olfactory Receptor Neuron Physiology
- Signal Transduction
Background:
- Odor stimulation of olfactory receptor neurons (ORNs) typically increases cAMP, opening cyclic nucleotide-gated (CNG) channels and causing depolarization.
- While CNG channel activation is the primary known mechanism, other ion conductances may be modulated by odorants.
Purpose of the Study:
- To investigate whether potassium (K+) conductances are modulated by odorants in mammalian ORNs.
- To elucidate the role of K+ conductance modulation in olfactory signal transduction.
Main Methods:
- Recording membrane current in rat ORNs using perforated-patch techniques.
- Applying various odorants to stimulate ORNs and observing changes in ion conductance.
- Characterizing the inhibited K+ conductance (IKo) pharmacologically and electrophysiologically.
Main Results:
- Odorant stimulation elicited two main responses in rat ORNs: 30% showed CNG channel activation, while 55% exhibited inhibition of a voltage-activated K+ conductance (IKo).
- The inhibited IKo shared characteristics with delayed rectifier K+ channels.
- Odorant-induced IKo inhibition was specific, concentration-dependent, and showed a latency, indicating an indirect mechanism.
Conclusions:
- Odorants can indirectly suppress a voltage-activated K+ conductance (IKo) in mammalian ORNs.
- This suppression of IKo represents a significant, previously underappreciated mechanism in olfactory signal transduction.
- Modulation of K+ conductances contributes to the complex processing of olfactory information.