Capsaicin facilitates excitatory but not inhibitory synaptic transmission in substantia gelatinosa of the rat spinal cord

Neurosci Lett. 1998 Oct 23;255(3):135-8. doi: 10.1016/s0304-3940(98)00730-7.


Actions of capsaicin were examined on synaptic transmissions in the substantia gelatinosa (SG) of adult rat spinal cord slices using the whole-cell patch-recording technique. Bath-applied capsaicin at a concentration of 2 microM activated a slow inward current (having an amplitude of 33 pA at -70 mV), which was accompanied by an increase in the frequency of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs; by 234%); these actions were blocked by a capsaicin-receptor antagonist, capsazepine (10 microM). The capsaicin-induced increase in sEPSC frequency was resistant to tetrodotoxin (0.5-1 microM). On the other hand, capsaicin (2 microM) did not affect either glycine- or gamma-aminobutyric acid-mediated spontaneous synaptic transmission. The results indicate that capsaicin enhances excitatory but not inhibitory synaptic transmission, possibly through a direct action on primary afferent terminals in the SG. As the SG has been thought to participate in nociceptive pathway, it is suggested that such a presynaptic action of capsaicin contributes to nociceptive transmissions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Capsaicin / pharmacology*
  • Excitatory Postsynaptic Potentials / drug effects*
  • Glycine / physiology
  • Neural Inhibition / drug effects*
  • Neural Inhibition / physiology
  • Neurons / drug effects
  • Neurons / physiology
  • Patch-Clamp Techniques
  • Rats
  • Rats, Sprague-Dawley
  • Substantia Gelatinosa / cytology
  • Substantia Gelatinosa / drug effects*
  • Substantia Gelatinosa / physiology
  • Synaptic Transmission / drug effects*
  • Synaptic Transmission / physiology
  • Tetrodotoxin / pharmacology
  • gamma-Aminobutyric Acid / physiology


  • Tetrodotoxin
  • gamma-Aminobutyric Acid
  • Capsaicin
  • Glycine