Spontaneously active NaV1.5 sodium channels may underlie odor sensitivity.

The olfactory system is remarkably sensitive to airborne odor molecules, but precisely how very low odor concentrations bordering on just a few molecules per olfactory sensory neuron can trigger graded changes in firing is not clear. This report reexamines signaling in olfactory sensory neurons in light of the recent account of NaV1.5 sodium channel-mediated spontaneous firing. Using a model of spontaneous channel activity, the study shows how even submillivolt changes in membrane potential elicited by odor are expected to cause meaningful changes in NaV1.5-dependent firing. The results suggest that the random window currents of NaV1.5 channels may underpin not only spontaneous firing in olfactory sensory neurons but the cellular response to odor as well, thereby ensuring the robustness and sensitivity of signaling that is especially important for low odor concentrations.