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Odorant-induced hyperpolarization and suppression of cAMP-activated current in newt olfactory receptor neurons
1Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan.
Abstract:
Although many studies have reported that odorants can elicit inhibitory responses as well as excitatory responses in vertebrate olfactory receptor neurons, the cellular mechanisms that underlie this inhibition are unclear. Here we examine the inhibitory effect of odorants on newt olfactory receptor neurons using whole cell patch clamp recording. At high concentrations, odorant stimulation decreased the membrane conductance and inhibited depolarization. Various odorants (anisole, isoamyl acetate, cineole, limonene and isovaleric acid) suppressed the depolarizing current in a dose-dependent manner. Furthermore, one odorant could suppress the depolarization caused by another odorant. The depolarization caused by isoamyl acetate was inhibited by anisole in cells that were excited by isoamyl acetate but not by anisole. Odorants were able to hyperpolarize cells that were depolarized by cAMP-induced conductance. Given that this inhibitory effect of odorants can affect excitation caused by other odorants, we suggest that it might play a role in coding odorants in olfactory receptor neurons.
Insights
Odorants can inhibit olfactory receptor neurons by decreasing membrane conductance, a finding important for understanding how smells are processed. This inhibitory effect may play a role in olfactory coding.
Area of Science:
- Neuroscience
- Olfactory system research
Background:
- Vertebrate olfactory receptor neurons (ORNs) exhibit both excitatory and inhibitory responses to odorants.
- The cellular mechanisms driving odorant-induced inhibition in ORNs remain largely unknown.
Purpose of the Study:
- To investigate the cellular mechanisms of odorant-induced inhibition in newt ORNs.
- To determine the role of odorant inhibition in olfactory coding.
Main Methods:
- Whole-cell patch-clamp recordings were used to analyze the electrophysiological responses of newt ORNs.
- Various odorants were applied at different concentrations to assess their inhibitory effects.
Main Results:
- High concentrations of odorants decreased membrane conductance and inhibited depolarization in ORNs.
- Odorant-induced suppression of depolarizing currents was dose-dependent.
- One odorant could inhibit the excitatory response caused by another odorant, suggesting cross-inhibition.
Conclusions:
- Odorant-induced inhibition involves decreased membrane conductance.
- This inhibitory mechanism may contribute to the neural coding of diverse odorants within the olfactory system.