Slow sodium conductances of dorsal root ganglion neurons: intraneuronal homogeneity and interneuronal heterogeneity

作者：Marco Rizzo, Jeffery D. Kocsis, S. G. Waxman · 发表于：Journal of Neurophysiology · 年份：1994 · DOI：10.1152/jn.1994.72.6.2796 · 被引用次数：126 · 研究领域：Ion channel regulation and function、Neuroscience and Neural Engineering、Neuroscience and Neuropharmacology Research

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), re...