Subclassified acutely dissociated cells of rat DRG: histochemistry and patterns of capsaicin-, proton-, and ATP-activated currents

J Neurophysiol. 2000 Nov;84(5):2365-79. doi: 10.1152/jn.2000.84.5.2365.


We used a "current signature" method to subclassify acutely dissociated dorsal root ganglion (DRG) cells into nine subgroups. Cells subclassified by current signature had uniform properties. The type 1 cell had moderate capsaicin sensitivity (25.9 pA/pF), powerful, slowly desensitizing (tau = 2,300 ms), ATP-activated current (13.3 pA/pF), and small nondesensitizing responses to acidic solutions (5.6 pA/pF). Type 1 cells expressed calcitonin gene-related peptide immunoreactivity (CGRP-IR), manifested a wide action potential (7.3 ms), long duration afterhyperpolarization (57.0 ms), and were IB4 positive. The type 2 cell exhibited large capsaicin activated currents (134.9 pA/pF) but weak nondesensitizing responses to protons (15.3 pA/pF). Currents activated by ATP and alphabeta-m-ATP (51.7 and 44.6 pA/pF, respectively) had fast desensitization kinetics (tau = 214 ms) that were distinct from all other cell types. Type 2 cells were IB4 positive but did not contain either substance P (SP) or CGRP-IR. Similar to capsaicin-sensitive nociceptors in vivo, the afterhyperpolarization of the type 2 cell was prolonged (54.7 ms). The type 3 cell expressed, amiloride-sensitive, rapidly desensitizing (tau = 683 ms) proton-activated currents (127.0 pA/pF), and was insensitive to ATP or capsaicin. The type 3 cell was IB4 negative and contained neither CGRP nor SP-IR. The afterhyperpolarization (17.5 ms) suggested nonnociceptive function. The type 4 cell had powerful ATP-activated currents (17.4 pA/pF) with slow desensitization kinetics (tau = 2, 813 ms). The afterhyperpolarization was prolonged (46.5 ms), suggesting that this cell type might belong to a capsaicin-insensitive nociceptor population. The type 4 cell did not contain peptides. The type 7 cell manifested amiloride-sensitive, proton-activated currents (45.8 pA/pF) with very fast desensitization kinetics (tau = 255 ms) and was further distinct from the type 3 cell by virtue of a nondesensitizing amiloride-insensitive component (6.0 pA/pF). Capsaicin and ATP sensitivity were relatively weak (4.3 and 2.9 pA/pF, respectively). Type 7 cells were IB4 positive and contained both SP and CGRP-IR. They exhibited an exceptionally long afterhyperpolarization (110 ms) that was suggestive of a silent (mechanically insensitive) nociceptor. We concluded that presorting of DRG cells by current signatures separated them into internally homogenous subpopulations that were distinct from other subclassified cell types.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Adenosine Triphosphate / pharmacology*
  • Animals
  • Calcitonin Gene-Related Peptide / analysis
  • Capsaicin / pharmacology*
  • Cluster Analysis
  • Ganglia, Spinal / chemistry
  • Ganglia, Spinal / cytology*
  • Lectins / pharmacology
  • Male
  • Neurons, Afferent / chemistry
  • Neurons, Afferent / classification*
  • Neurons, Afferent / physiology*
  • Nociceptors / physiology
  • Pain / physiopathology
  • Patch-Clamp Techniques
  • Protons
  • Rats
  • Rats, Sprague-Dawley
  • Substance P / analysis


  • Lectins
  • Protons
  • Substance P
  • Adenosine Triphosphate
  • Calcitonin Gene-Related Peptide
  • Capsaicin