کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4332388 1292896 2006 6 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Fast cholinergic efferent inhibition in guinea pig outer hair cells
موضوعات مرتبط
علوم زیستی و بیوفناوری علم عصب شناسی علوم اعصاب (عمومی)
پیش نمایش صفحه اول مقاله
Fast cholinergic efferent inhibition in guinea pig outer hair cells
چکیده انگلیسی
Hair cells of inner ear are suggested to be inhibited by the activation of the α9-containing nicotinic acetylcholine (ACh) receptors (α9-containing nAChRs). Several studies have suggested that the native nicotinic-like ACh receptors (nAChRs) in hair cells display a significant permeability of Ca2+ ions and unusual pharmacological properties. The activation of native nAChRs will initiate the hyperpolarization of hair cells by activation of the small conductance, Ca2+-activated K+ channels (SK). In this work, the properties of the ACh-sensitive potassium current (IK(ACh)) in outer hair cells (OHCs) of guinea pigs were investigated by employing whole-cell patch-clamp. Followed by perfusion of ACh, OHCs displayed a rapid desensitized current with an N-shaped current-voltage curve (I-V) and a reversal potential of − 66 ± 7 mV. The IK(ACh) was still present during perfusion of either iberiotoxin (IBTX, 200 nM) or TEA (5 mM) but was potently inhibited by apamin (1 μM), TEA (30 mM). The IK(ACh) demonstrated a strong sensitivity to α-bungarotoxin (α-BgTx), bicuculline and strychnine. These results suggested that OHCs display the well-known SK current, which might be gated by the α9-containing nAChRs. Two important changes were present after lowering the Ca2+ concentration in the external conditions from 2 mM to 0.2 mM: one was a flattened N-shape I-V relationship with a maximum shifted toward hyperpolarized potentials from −20 ∼ −30 mV ∼ −40 to −50 mV, the other was a significant reduction in the agonist maximal response (percentage of maximal response 10.5 ± 5.4). These results indicated that native nAChRs are both permeable to and modulated by extracellular Ca2+ ions. Taken together, this work provides direct evidences that SK channels in OHCs of guinea pigs are gated by α9-containing nAChRs, which play an important role in the fast cholinergic efferent inhibition. This fast inhibition is both potently dependent on the permeability of Ca2+ ions through the native nAChRs and modulated by Ca2+ ions.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Brain Research - Volume 1102, Issue 1, 2 August 2006, Pages 103-108
نویسندگان
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