Localization and Function of the Kv3.1b Subunit in the Rat Medulla Oblongata: Focus on the Nucleus Tractus Solitarii

J Physiol. 2005 Feb 1;562(Pt 3):655-72. doi: 10.1113/jphysiol.2004.073338. Epub 2004 Nov 4.

Abstract

The voltage-gated potassium channel subunit Kv3.1 confers fast firing characteristics to neurones. Kv3.1b subunit immunoreactivity (Kv3.1b-IR) was widespread throughout the medulla oblongata, with labelled neurones in the gracile, cuneate and spinal trigeminal nuclei. In the nucleus of the solitary tract (NTS), Kv3.1b-IR neurones were predominantly located close to the tractus solitarius (TS) and could be GABAergic or glutamatergic. Ultrastructurally, Kv3.1b-IR was detected in NTS terminals, some of which were vagal afferents. Whole-cell current-clamp recordings from neurones near the TS revealed electrophysiological characteristics consistent with the presence of Kv3.1b subunits: short duration action potentials (4.2 +/- 1.4 ms) and high firing frequencies (68.9 +/- 5.3 Hz), both sensitive to application of TEA (0.5 mm) and 4-aminopyridine (4-AP; 30 mum). Intracellular dialysis of an anti-Kv3.1b antibody mimicked and occluded the effects of TEA and 4-AP in NTS and dorsal column nuclei neurones, but not in dorsal vagal nucleus or cerebellar Purkinje cells (which express other Kv3 subunits, but not Kv3.1b). Voltage-clamp recordings from outside-out patches from NTS neurones revealed an outward K(+) current with the basic characteristics of that carried by Kv3 channels. In NTS neurones, electrical stimulation of the TS evoked EPSPs and IPSPs, and TEA and 4-AP increased the average amplitude and decreased the paired pulse ratio, consistent with a presynaptic site of action. Synaptic inputs evoked by stimulation of a region lacking Kv3.1b-IR neurones were not affected, correlating the presence of Kv3.1b in the TS with the pharmacological effects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Electroencephalography
  • Medulla Oblongata / cytology
  • Medulla Oblongata / physiology
  • Nerve Tissue Proteins / physiology*
  • Neural Pathways / cytology
  • Neural Pathways / physiology
  • Neurons / cytology*
  • Neurons / physiology*
  • Potassium Channels, Voltage-Gated / physiology*
  • Rats
  • Rats, Wistar
  • Shaw Potassium Channels
  • Solitary Nucleus / cytology*
  • Solitary Nucleus / physiology*
  • Synaptic Transmission / physiology*
  • Tissue Distribution

Substances

  • Kcnc1 protein, rat
  • Nerve Tissue Proteins
  • Potassium Channels, Voltage-Gated
  • Shaw Potassium Channels