Rothman JS, Manis PB. Differential expression of three distinct potassium currents in the ventral cochlear nucleus.
J Neurophysiol 2003;
89:3070-82. [PMID:
12783951 DOI:
10.1152/jn.00125.2002]
[Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In the ventral cochlear nucleus (VCN), neurons transform information from auditory nerve fibers into a set of parallel ascending pathways, each emphasizing different aspects of the acoustic environment. Previous studies have shown that VCN neurons differ in their intrinsic electrical properties, including the K+ currents they express. In this study, we examine these K+ currents in more detail using whole cell voltage-clamp techniques on isolated VCN cells from adult guinea pigs at 22 degrees C. Our results show a differential expression of three distinct K+ currents. Whereas some VCN cells express only a high-threshold delayed-rectifier-like current (IHT), others express IHT in combination with a fast inactivating current (IA) and/or a slow-inactivating low-threshold current (ILT). IHT, ILT, and IA, were partially blocked by 1 mM 4-aminopyridine. In contrast, only ILT was blocked by 10-100 nM dendrotoxin-I. A surprising finding was the wide range of levels of ILT, suggesting ILT is expressed as a continuum across cell types rather than modally in a particular cell type. IA, on the other hand, appears to be expressed only in cells that show little or no ILT, the Type I cells. Boltzmann analysis shows IHT activates with 164 +/- 12 (SE) nS peak conductance, -14.3 +/- 0.7 mV half-activation, and 7.0 +/- 0.5 mV slope factor. Similar analysis shows ILT activates with 171 +/- 22 nS peak conductance, -47.4 +/- 1.0 mV half-activation, and 5.8 +/- 0.3 mV slope factor.
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