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Titolo:
Potassium currents in octopus cells of the mammalian cochlear nucleus
Autore:
Bal, R; Oertel, D;
Indirizzi:
Univ Wisconsin, Sch Med, Dept Physiol, Madison, WI 53706 USA Univ Wisconsin Madison WI USA 53706 , Dept Physiol, Madison, WI 53706 USA
Titolo Testata:
JOURNAL OF NEUROPHYSIOLOGY
fascicolo: 5, volume: 86, anno: 2001,
pagine: 2299 - 2311
SICI:
0022-3077(200111)86:5<2299:PCIOCO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
GATED K+ CHANNELS; DENDROTOXIN-BINDING-SITE; AUDITORY-NERVE FIBERS; XENOPUS-OOCYTES; LATERAL LEMNISCUS; VENTRAL NUCLEUS; RAT-BRAIN; DIFFERENTIAL EXPRESSION; HORSERADISH-PEROXIDASE; SUBUNIT COMPOSITION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
67
Recensione:
Indirizzi per estratti:
Indirizzo: Oertel, D Univ Wisconsin, Sch Med, Dept Physiol, 1300 Univ Ave, Madison, WI 53706 USA Univ Wisconsin 1300 Univ Ave Madison WI USA 53706 , WI 53706 USA
Citazione:
R. Bal e D. Oertel, "Potassium currents in octopus cells of the mammalian cochlear nucleus", J NEUROPHYS, 86(5), 2001, pp. 2299-2311

Abstract

Octopus cells in the posteroventral cochlear nucleus (PVCN) of mammals arebiophysically specialized to detect coincident firing in the population ofauditory nerve fibers that provide their synaptic input and to convey its occurrence with temporal precision. The precision in the timing of action potentials depends on the low input resistance (similar to6 M Omega) of octopus cells at the resting potential that makes voltage changes rapid (tau similar to 200 mus). It is the activation of voltage-dependent conductances that endows octopus cells with low input resistances and prevents repetitivefiring in response to depolarization. These conductances have been examined under whole cell voltage clamp. The present study reveals the properties of two conductances that mediate currents whose reversal at or near the equilibrium potential for K+ over a wide range of extracellular K+ concentrations identifies them as K+ currents. One rapidly inactivating conductance, g(KL), had a threshold of activation at -70 mV, rose steeply as a function of depolarization with half-maximal activation at -45 +/-6 mV (mean +/- SD),and was fully activated at 0 mV. The low-threshold K+ current (I-KL) was largely blocked by alpha -dendrotoxin (alpha -DTX) and partially blocked by DTX-K and tityus-toxin, indicating that this current was mediated through potassium channels of the Kv1 (also known as shaker or KCNA) family. The maximum low-threshold K+ conductance (g(KL)) was large, 514 +/- 135 nS. Blocking I-KL with alpha -DTX revealed a second K+ current with a higher threshold (I-KH) that was largely blocked by 20 mM tetraethylammonium (TEA). The more slowly inactivating conductance, g KH, had a threshold for activation at-40 mV, reached half-maximal activation at -16 +/-5 mV, and was fully activated at +30 mV. The maximum high-threshold conductance, g(KH), was on average 116 +/- 27 nS. The present experiments show that it is not the biophysical and pharmacological properties but the magnitude of the K+ conductancesthat make octopus cells unusual. At the resting potential, -62 mV, g(KL) contributes similar to 42 nS to the resting conductance and mediates a resting K+ current of 1 nA. The resting outward K+ current is balanced by an inward current through the hyperpolarization-activated conductance, g(h), thathas been described previously.

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Documento generato il 05/12/20 alle ore 01:00:41