Excitability of the Adelta nociceptive pathways as assessed by the recovery cycle of laser evoked potentials in humans

Exp Brain Res. 2004 Mar;155(1):120-3. doi: 10.1007/s00221-003-1785-x. Epub 2004 Jan 17.


To investigate the excitability of Adelta nociceptive pathways and the nature of the vertex laser evoked potentials (LEPs), we studied the recovery cycle of the P2-LEP component and compared it with that of the P200 of the somatosensory evoked potential (SEP). Using two identical CO(2)-laser stimulators, we delivered paired stimuli to two adjacent skin spots on the hand at interstimulus intervals ranging from 250 ms to 2 s. The test P2-LEP was strongly inhibited at the 250-ms interstimulus interval ( P<0.01) and progressively recovered by the 2-s interval. The P200-SEP, after paired stimuli to the median nerve, showed a time course even slower than the P2-LEP ( P<0.01). Besides providing the LEP recovery curve in normal subjects, our findings indicate that the P2-LEP relays through a number of synapses similar to (or even lower than) that for the P200-SEP, thus lending further support to the view that the nociceptive P2-LEP is not an endogenous potential equivalent to the P300.

MeSH terms

  • Adult
  • Electric Stimulation / methods
  • Evoked Potentials, Somatosensory / physiology*
  • Hot Temperature
  • Humans
  • Lasers*
  • Nerve Fibers / physiology*
  • Neural Pathways / physiology
  • Nociceptors / physiology*
  • Pain Measurement / methods
  • Pain Threshold / physiology
  • Recovery of Function / physiology*