Capsaicin sensitivity and voltage-gated sodium currents in colon sensory neurons from rat dorsal root ganglia

Am J Physiol. 1999 Dec;277(6):G1180-8. doi: 10.1152/ajpgi.1999.277.6.G1180.

Abstract

DiI-labeled colon sensory neurons were acutely dissociated from S1 rat dorsal root ganglia (DRG) and studied using perforated whole cell patch-clamp techniques. Forty-six percent (54/116) of labeled sensory neurons responded to capsaicin (10(-8)- 10(-5) M) with an increase in inward current, which was a nonspecific cation conductance. Responses to capsaicin applied by puffer ejection were dependent on dose, with a half-maximal response at 4.9 x 10(-7) M; bath application was characterized by marked desensitization. Voltage-gated Na(+) currents in 23 of 30 DRG cells exhibited both TTX-sensitive and TTX-resistant components. In these cells, capsaicin induced an inward current in 11 of 17 cells tested. Of the cells containing only a TTX-sensitive component, none of six cells tested was sensitive to capsaicin. In all cells that responded to capsaicin with an increase in inward current, capsaicin abolished voltage-gated Na(+) currents (n = 21). Capsazepine (10(-6) M) significantly attenuated both the increase in inward current and the reduction in Na(+) currents. Na(+) currents were not significantly altered by adenosine, bradykinin, histamine, PGE(2), or serotonin at 10(-6) M and 10(-5) M. These findings may have important implications for understanding both the irritant and analgesic properties of capsaicin.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Adenosine / pharmacology
  • Analgesics / pharmacology
  • Animals
  • Bradykinin / pharmacology
  • Capsaicin / pharmacology*
  • Carbocyanines
  • Colon / innervation*
  • Dinoprostone / pharmacology
  • Dose-Response Relationship, Drug
  • Electrophysiology
  • Fluorescent Dyes
  • Ganglia, Spinal / cytology*
  • Ganglia, Spinal / drug effects
  • Histamine / pharmacology
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Male
  • Neurons, Afferent / chemistry
  • Neurons, Afferent / drug effects*
  • Pain / physiopathology
  • Rats
  • Rats, Sprague-Dawley
  • Serotonin / pharmacology
  • Sodium / metabolism
  • Sodium Channels / physiology*
  • Tetrodotoxin / pharmacology

Substances

  • Analgesics
  • CM-DiI
  • Carbocyanines
  • Fluorescent Dyes
  • Sodium Channels
  • Serotonin
  • Tetrodotoxin
  • Histamine
  • Sodium
  • Adenosine
  • Dinoprostone
  • Capsaicin
  • Bradykinin