title: Differential expression of three distinct potassium currents in the ventral cochlear nucleus.
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.
authors.affiliation: The Center for Hearing Science, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Jason S
authors.initials: JS
authors.lastname: Rothman
authors.forename: Paul B
authors.initials: PB
authors.lastname: Manis
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D018929:Cell Culture Techniques; D017626:Cochlear Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004546:Elapid Venoms / Q000494:pharmacology; D006168:Guinea Pigs; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
chemical_list: D004546:Elapid Venoms; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C020273:dendrotoxin; D015761:4-Aminopyridine