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Role of the Low‐voltage Activated Ca 2+ Current (LVA) in the Vestibular Afferent Neurons in Culture
Author(s) -
Galván Maricruz Rangel,
Vega y Saenz de Miera María Rosario,
Eguibar Enrique Soto
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1224.36
Subject(s) - depolarization , hyperpolarization (physics) , mibefradil , electrophysiology , chemistry , patch clamp , voltage clamp , neuroscience , afterhyperpolarization , biophysics , soma , physics , voltage dependent calcium channel , biology , calcium , stereochemistry , organic chemistry , nuclear magnetic resonance spectroscopy
Vestibular‐afferent neurons (VANs) resting electrical discharge may vary from regular to irregular action potential intervals spanning a continuum of variation coefficients. The specific firing properties of each neuron are correlated with the soma size and the synaptic input, however, firing patterns of these neurons cannot be explained completely by means of those characteristics. It has been proposed that intrinsic properties (variable expression and density of the ion channels) contribute to establish the firing pattern observed in VANs. It has been found that the after‐hyperpolarization phase (AHP) of the action potential (AP) is an essential component determining the firing regularity of VANs. The AHP involve the activation of the hyperpolarization‐activated current (I h ), Ca 2+ ‐activated K + current (IK Ca ), Na + ‐activated K + current (IK Na ), low‐voltage activated K + current (IK LV ) and low‐voltage activated Ca 2+ current (LVA). Based on previous results it has been suggested that heterogeneous distribution of the LVA currents contribute to differentiate the discharge pattern of VANs. Here, we study the functional role of LVA current on VANs‐discharge. Using whole‐cell patch‐clamp recording, we observed a blocking effect of Nickel (300 μM) and Mibefradil (2 μM) on LVA currents. Current‐clamp recordings showed that Ni 2+ modified the morphology of action potentials (AP), decreasing the amplitude and increasing the duration of the AP, on the other hand Mibefradil decreased amplitude and threshold (T) of the AP. Moreover, the frequency of the repetitive firing generated by a long depolarization pulse (1.5 × T) was decreased after applying both Ni 2+ and Mibefradil blockers. Discharge regularity is measured by a coefficient of variation (CV) of interspike intervals obtained with a Gaussian white noise stimulation protocol. LVA current blocked with Mibefradil produced a trend toward regular firing. Sinusoidal stimuli shown a group of cells in which the AP number increased and another group where the AP number decreased. Our results showed that VANs possess a LVA current and that their heterogeneous expression would contribute to explain some of the differences in the discharge pattern in these neurons. Support or Funding Information Dr. Enrique Soto EguibarInstitute of Physiology ‐ BUAP A.P. 406Puebla, Pue. Postal code: 72570 MexicoTel: (52‐222) 2295500 est 7316Fax: (52‐222) 2295500 ext 7301