Localization and function of the Kv3.1b subunit in the rat medulla oblongata: focus on the nucleus tractus solitarii.
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.
Dallas
Mark L
ML
School of Biomedical Sciences, Worsley Building, University of Leeds, Leeds LS2 9NQ, UK.
Atkinson
Lucy
L
Milligan
Carol J
CJ
Morris
Neil P
NP
Lewis
David I
DI
Deuchars
Susan A
SA
Deuchars
Jim
J
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D004569:Electroencephalography; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D051670:Shaw Potassium Channels; D017552:Solitary Nucleus / Q000166:cytology* / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014018:Tissue Distribution
C098254:Kcnc1 protein, rat; D009419:Nerve Tissue Proteins; D024642:Potassium Channels, Voltage-Gated; D051670:Shaw Potassium Channels