» Articles » PMID: 7897490

Slow Sodium Conductances of Dorsal Root Ganglion Neurons: Intraneuronal Homogeneity and Interneuronal Heterogeneity

Overview
Journal J Neurophysiol
Specialties Neurology
Physiology
Date 1994 Dec 1
PMID 7897490
Citations 38
Authors
Affiliations
Soon will be listed here.
Abstract

1. Voltage-dependent Na+ conductances were studied in small (18-25 microns diam) adult rat dorsal root ganglion (DRG) neurons with the use of the whole cell patch-clamp technique. Na+ currents were also recorded from larger (44-50 microns diam) neurons and compared with those of the small neurons. 2. The predominant Na+ conductance in the small neurons was selective over tetramethylammonium by at least 10-fold and was resistant to 1 microM external tetrodotoxin (TTX). Na+ conductances in many larger DRG neurons were kinetically faster and, in contrast, were blocked by 1 microM TTX. 3. The Na+ conductance in the small neurons was kinetically slow. Activation half-times were voltage dependent and ranged from 2 ms at -20 mV to 0.7 ms at +50 mV. Approximately 50% of the activation half-time was comprised of an initial delay. Inactivation half-times were voltage dependent and ranged from 11 ms at -20 mV to 2 ms at +50 mV. 4. Peak slow Na+ conductances were near maximal with conditioning potentials negative to -120 mV and were significantly reduced or eliminated with conditioning potentials positive to -40 mV. The slow Na+ conductance increased gradually with test potentials extending from -40 to +40 mV. In some cells the conductance could be saturated at +10 mV. Peak conductance/voltage relationships, although stable in a given neuron, revealed marked variability among neurons, spanning > 20- and 50-mV domains for steady-state activation and inactivation (current availability), respectively. 5. Kinetics remained stable within a given neuron over the course of an experiment. However, considerable kinetic variation was exhibited from neuron to neuron, such that the half-times of activation and of inactivation spanned an order of magnitude. In all small neurons studied there appeared to be a singular kinetic component of the current, based on sensitivity to the conditioning potential, voltage dependence of activation, and inactivation half-time. 6. Unique closing properties were exhibited by Na+ channels of the small neurons. Hyperpolarization following a depolarization-induced fully inactivated state resulted in tail currents that appeared to be the consequence of reactivation of the slow Na+ conductance. Tail currents recorded at various times during a fixed level of depolarization revealed that the underlying channels accumulated into a volatile inactivated state over the course of the preceding depolarization.(ABSTRACT TRUNCATED AT 400 WORDS)

Citing Articles

Dorsal root ganglion neurons recapitulate the traumatic axonal injury of CNS neurons in response to a rapid stretch .

Adams A, Li Y, Kim H, Pfister B Front Cell Neurosci. 2023; 17:1111403.

PMID: 37066078 PMC: 10090399. DOI: 10.3389/fncel.2023.1111403.


Polysorbate 80 blocked a peripheral sodium channel, Na1.7, and reduced neuronal excitability.

Kim R, Choi J Mol Pain. 2022; 19:17448069221150138.

PMID: 36550597 PMC: 9829885. DOI: 10.1177/17448069221150138.


Differential modulation of voltage-gated sodium channels by nerve growth factor in three major subsets of TrkA-expressing nociceptors.

Schaefer I, Prato V, Arcourt A, Taberner F, Lechner S Mol Pain. 2018; 14:1744806918814640.

PMID: 30387376 PMC: 6856966. DOI: 10.1177/1744806918814640.


Tolerance to Morphine-Induced Inhibition of TTX-R Sodium Channels in Dorsal Root Ganglia Neurons Is Modulated by Gut-Derived Mediators.

Mischel R, Dewey W, Akbarali H iScience. 2018; 2:193-209.

PMID: 29888757 PMC: 5993194. DOI: 10.1016/j.isci.2018.03.003.


Sodium channels and pain: from toxins to therapies.

Cardoso F, Lewis R Br J Pharmacol. 2017; 175(12):2138-2157.

PMID: 28749537 PMC: 5980290. DOI: 10.1111/bph.13962.


References
1.
Yoshida S, Matsuda Y . Studies on sensory neurons of the mouse with intracellular-recording and horseradish peroxidase-injection techniques. J Neurophysiol. 1979; 42(4):1134-45. DOI: 10.1152/jn.1979.42.4.1134. View

2.
Fukuda J, Kameyama M . Tetrodotoxin-sensitive and tetrodotoxin-resistant sodium channels in tissue-cultured spinal ganglion neurons from adult mammals. Brain Res. 1980; 182(1):191-7. DOI: 10.1016/0006-8993(80)90844-6. View

3.
Catterall W . Neurotoxins that act on voltage-sensitive sodium channels in excitable membranes. Annu Rev Pharmacol Toxicol. 1980; 20:15-43. DOI: 10.1146/annurev.pa.20.040180.000311. View

4.
Pappone P . Voltage-clamp experiments in normal and denervated mammalian skeletal muscle fibres. J Physiol. 1980; 306:377-410. PMC: 1283012. DOI: 10.1113/jphysiol.1980.sp013403. View

5.
Sigworth F . The variance of sodium current fluctuations at the node of Ranvier. J Physiol. 1980; 307:97-129. PMC: 1283036. DOI: 10.1113/jphysiol.1980.sp013426. View