Na(V)1.5 sodium channel window currents contribute to spontaneous firing in olfactory sensory neurons

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 Zn2+ 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.This work was aided by support from Boston University, the Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD) P30 DC-04657; D. Restrepo, principal investigator], and NIDCD Grants DC-04863 to V. Dionne and DC-006070 to D. Restrepo and T. E. Finger. (Boston University; P30 DC-04657 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)]; DC-04863 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)]; DC-006070 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)])https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122723/Accepted manuscrip

Inclusive quasielastic electron scattering on 6^6He: a probe of the halo structure

We investigate inclusive electron scattering reactions on two-neutron halo nuclei in the quasielastic region. Expressions for the cross section and structure functions are given assuming that the halo nucleus can be described as a three-body system (${core}+n+n$). The method is applied to $^6$He. We compute cross sections and structure functions, and investigate the kinematic conditions for which the observables are determined either by $\alpha$-knockout or by halo neutron-knockout. The optimal kinematical domain to disantangle the momentum distributions of the various components of the three--body system ($q \lesssim 200$ MeV/c and $\omega < q^2/2M_N + 20$ MeV) are explored.Comment: 10 pages, 3 figures. Physics Letters B, in pres

Artsbestemmelse av meitemark

I Norge er det funnet 19 arter meitemark. Av disse er 5-7 vanlige i dyrka jord. Ved hjelp av denne nøkkelen kan du artsbestemme voksne, levende individer av de 5 vanligste artene i dyrka jord og kompost. Størrelse og farge på dyret er viktig, andre kjennetegn er funnsted og hvordan marken beveger seg

Meitemark og jordforbedring

This leaflet presents knowledge about earthworms and their impact on soil structure, based on research projects conducted in Norway. Target group : Farmers and gardeners

Studer meitemark ved å grave jordprofil

Med litt trening og kunnskap kan du se effekter av drifta på jordstruktur, rotutvikling og meitemarkens arbeid i jorda. Særlig der veksten er dårlig kan et jordprofil gi informasjon om hvor problemene ligger. Det kan være spennende å grave et slikt hull i jorda, særlig sammen med andre praktikere og rådgivere. Da blir det gjerne gode diskusjoner om agronomi, drift og maskinpark

Salt content in canteen and fast food meals in Denmark

Background: A high salt (=NaCl) intake is associated with high blood pressure, and knowledge of salt content in food and meals is important, if the salt intake has to be decreased in the general population. Objective: To determine the salt content in worksite canteen meals and fast food. Design: For the first part of this study, 180 canteen meals were collected from a total of 15 worksites with in-house catering facilities. Duplicate portions of a lunch meal were collected from 12 randomly selected employees at each canteen on two non-consecutive days. For the second part of the study, a total of 250 fast food samples were collected from 52 retail places representing both city (Aarhus) and provincial towns. The canteen meals and fast food samples were analyzed for chloride by potentiometric titration with silver nitrate solution, and the salt content was estimated. Results: The salt content in lunch meals in worksite canteens were 3.8&#x00B1;1.8 g per meal and 14.7&#x00B1;5.1 g per 10 MJ for men (n=109), and 2.8&#x00B1;1.2 g per meal and 14.4&#x00B1;6.2 g per 10 MJ for women (n=71). Salt content in fast food ranged from 11.8&#x00B1;2.5 g per 10 MJ (burgers) to 16.3&#x00B1;4.4 g per 10 MJ (sausages) with a mean content of 13.8&#x00B1;3.8 g per 10 MJ. Conclusion: Salt content in both fast food and in worksite canteen meals is high and should be decreased

Electron scattering on two-neutron halo nuclei: The case of 6^6He

The formalism to describe electron scattering reactions on two-neutron halo nuclei is developed. The halo nucleus is described as a three-body system (core+n+n), and the wave function is obtained by solving the Faddeev equations in coordinate space. We discuss elastic and quasielastic scattering using the impulse approximation to describe the reaction mechanism. We apply the method to investigate the case of electron scattering on $^6$He. Spectral functions, response functions, and differential cross sections are calculated for both neutron knockout and $\alpha$ knockout by the electron.Comment: 17 pages, figures include

Momentum Distributions of Particles from Three--Body Halo Fragmentation: Final State Interactions

Momentum distributions of particles from nuclear break-up of fast three-body halos are calculated consistently, and applied to $^{11}$Li. The same two-body interactions between the three particles are used to calculate the ground state structure and the final state of the reaction processes. We reproduce the available momentum distributions from $^{11}$Li fragmentation, together with the size and energy of $^{11}$Li, with a neutron-core relative state containing a $p$-state admixture of 20\%-30\%. The available fragmentation data strongly suggest an $s$-state in $^{10}$Li at about 50 keV, and indicate a $p$-state around 500 keV.Comment: 11 pages (RevTeX), 3 Postscript figures (uuencoded postscript file attached at the end of the LaTeX file). To be published in Phys. Rev.