Experimental nerve block study on painful withdrawal reflex responses in humans.
PLoS One
; 19(8): e0309048, 2024.
Article
em En
| MEDLINE
| ID: mdl-39150939
ABSTRACT
The nociceptive withdrawal reflex (NWR) is a protective limb withdrawal response triggered by painful stimuli, used to assess spinal nociceptive excitability. Conventionally, the NWR is understood as having two reflex responses a short-latency Aß-mediated response, considered tactile, and a longer-latency Aδ-mediated response, considered nociceptive. However, nociceptors with conduction velocities similar to Aß tactile afferents have been identified in human skin. In this study, we investigated the effect of a preferential conduction block of Aß fibers on pain perception and NWR signaling evoked by intradermal electrical stimulation in healthy participants. We recorded a total of 198 NWR responses in the intact condition, and no dual reflex responses occurred within our latency bandwidth (50-150 ms). The current required to elicit the NWR was higher than the perceptual pain threshold, indicating that NWR did not occur before pain was felt. In the block condition, when the Aß-mediated tuning fork sensation was lost while Aδ-mediated nonpainful cooling was still detectable (albeit reduced), we observed that the reflex was abolished. Further, short-latency electrical pain intensity at pre-block thresholds was greatly reduced, with any residual pain sensation having a longer latency. Although electrical pain was unaffected at suprathreshold current, the reflex could not be evoked despite a two-fold increase in the pre-block current and a five-fold increase in the pre-block pulse duration. These observations lend support to the possible involvement of Aß-fiber inputs in pain and reflex signaling.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Reflexo
/
Estimulação Elétrica
Limite:
Adult
/
Female
/
Humans
/
Male
Idioma:
En
Revista:
PLoS One
Assunto da revista:
CIENCIA
/
MEDICINA
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Austrália
País de publicação:
Estados Unidos