Transient inhibition of the human motor cortex by capsaicin-induced pain. A study with transcranial magnetic stimulation

Neurosci Lett. 2001 Nov 13;314(1-2):97-101. doi: 10.1016/s0304-3940(01)02297-2.


Motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) of the left motor cortex were recorded from the right first dorsal interosseous (FDI), abductor pollicis brevis (APB), abductor digiti minimi (ADM), flexor carpi radialis (FCR), extensor carpi radialis (ECR) in 17 normal subjects, before and after painful application of capsaicin on the skin overlying the right FDI and FCR muscles. The amplitude of MEPs from the FDI and FCR was significantly reduced from 20 to 30 min after the application of capsaicin over the FDI and FCR muscles, respectively, then progressively returned to the basal values. A similar trend of MEPs inhibition was observed for APB and FCR muscles, but this reduction was not significant. Indices of peripheral nerve (M-wave) and spinal cord excitability (F and H waves) did not change throughout the experiments. Motor cortex inhibition induced by tonic cutaneous pain is maximal to muscles adjacent to the painful area. This inhibition may be due to the activation of the C fibres which mediate 'slow' nociception and might be important to alert subject to possible phasic nociceptive events that may occur close to the painful area.

MeSH terms

  • Adult
  • Afferent Pathways / drug effects
  • Afferent Pathways / physiology*
  • Capsaicin / adverse effects*
  • Efferent Pathways / drug effects
  • Efferent Pathways / physiology
  • Electric Stimulation
  • Electromyography
  • Evoked Potentials, Motor / drug effects
  • Evoked Potentials, Motor / physiology*
  • Female
  • Functional Laterality / physiology
  • Humans
  • Male
  • Motor Cortex / physiology*
  • Muscle Contraction / drug effects
  • Muscle Contraction / physiology
  • Neural Inhibition / drug effects
  • Neural Inhibition / physiology*
  • Neural Pathways / physiology
  • Nociceptors / drug effects
  • Nociceptors / physiology*
  • Pain / chemically induced
  • Pain / physiopathology*
  • Pain Measurement
  • Skin / drug effects
  • Skin / innervation
  • Somatosensory Cortex / physiology
  • Transcranial Magnetic Stimulation


  • Capsaicin