• Home
  • Search Results
  • NaV1.5 sodium channel window currents contribute to spontaneous firing in olfactory sensory neurons.

NaV1.5 sodium channel window currents contribute to spontaneous firing in olfactory sensory neurons.

Journal of neurophysiology (2014-05-30)
Christopher T Frenz, Anne Hansen, Nicholas D Dupuis, Nicole Shultz, Simon R Levinson, Thomas E Finger, Vincent E Dionne
ABSTRACT

Olfactory sensory neurons (OSNs) fire spontaneously as well as in response to odor; both forms of firing are physiologically important. We studied voltage-gated Na(+) channels in OSNs to assess their role in spontaneous activity. Whole cell patch-clamp recordings from OSNs demonstrated both tetrodotoxin-sensitive and tetrodotoxin-resistant components of Na(+) current. RT-PCR showed mRNAs for five of the nine different Na(+) channel α-subunits in olfactory tissue; only one was tetrodotoxin resistant, the so-called cardiac subtype NaV1.5. Immunohistochemical analysis indicated that NaV1.5 is present in the apical knob of OSN dendrites but not in the axon. The NaV1.5 channels in OSNs exhibited two important features: 1) a half-inactivation potential near -100 mV, well below the resting potential, and 2) a window current centered near the resting potential. The negative half-inactivation potential renders most NaV1.5 channels in OSNs inactivated at the resting potential, while the window current indicates that the minor fraction of noninactivated NaV1.5 channels have a small probability of opening spontaneously at the resting potential. When the tetrodotoxin-sensitive Na(+) channels were blocked by nanomolar tetrodotoxin at the resting potential, spontaneous firing was suppressed as expected. Furthermore, selectively blocking NaV1.5 channels with Zn(2+) in the absence of tetrodotoxin also suppressed spontaneous firing, indicating that NaV1.5 channels are required for spontaneous activity despite resting inactivation. We propose that window currents produced by noninactivated NaV1.5 channels are one source of the generator potentials that trigger spontaneous firing, while the upstroke and propagation of action potentials in OSNs are borne by the tetrodotoxin-sensitive Na(+) channel subtypes.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, anhydrous, ≥99.5%
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, for molecular biology
Sigma-Aldrich
Ethyl alcohol, Pure, 190 proof, meets USP testing specifications
Sigma-Aldrich
Ethyl alcohol, Pure, 190 proof, ACS spectrophotometric grade, 95.0%
Sigma-Aldrich
Ethanol, anhydrous, denatured
Sigma-Aldrich
2-Propanol, BioReagent, for molecular biology, ≥99.5%
Sigma-Aldrich
2-Propanol, suitable for HPLC, 99.9%
Sigma-Aldrich
HEPES, ≥99.5% (titration)
Sigma-Aldrich
2-Propanol, ACS reagent, ≥99.5%
Sigma-Aldrich
Chloroform, contains 100-200 ppm amylenes as stabilizer, ≥99.5%
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, ACS reagent, ≥99.5%
Sigma-Aldrich
Sodium chloride, BioXtra, ≥99.5% (AT)
Sigma-Aldrich
HEPES, BioPerformance Certified, ≥99.5% (titration), suitable for cell culture
Sigma-Aldrich
2-Propanol, anhydrous, 99.5%
Sigma-Aldrich
Sodium chloride, for molecular biology, DNase, RNase, and protease, none detected, ≥99% (titration)
Sigma-Aldrich
Chloroform, anhydrous, ≥99%, contains 0.5-1.0% ethanol as stabilizer
Sigma-Aldrich
Sodium chloride solution, 0.9% in water, BioXtra, suitable for cell culture
Sigma-Aldrich
Sodium chloride, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥99%
Sigma-Aldrich
L-Cysteine, 97%
Sigma-Aldrich
2-Propanol, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.8% (GC)
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, HPLC/spectrophotometric grade
Sigma-Aldrich
Isopropyl alcohol, ≥99.7%, FCC, FG
Sigma-Aldrich
Ethidium bromide solution, BioReagent, for molecular biology, 10 mg/mL in H2O
Sigma-Aldrich
Sodium chloride solution, 5 M in H2O, BioReagent, for molecular biology, suitable for cell culture
Sigma-Aldrich
Chloroform, anhydrous, contains amylenes as stabilizer, ≥99%
Sigma-Aldrich
HEPES buffer solution, 1 M in H2O
Sigma-Aldrich
Chloroform, HPLC Plus, for HPLC, GC, and residue analysis, ≥99.9%, contains amylenes as stabilizer
Sigma-Aldrich
L-Cysteine, from non-animal source, BioReagent, suitable for cell culture, ≥98%
Sigma-Aldrich
Sodium chloride solution, 5 M
Sigma-Aldrich
Chloroform, suitable for HPLC, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer