Axotomy- and Autotomy-Induced Changes in the Excitability of Rat Dorsal Root Ganglion Neurons
Notice bibliographique
Résumé
The spontaneous, ectopic activity in sensory nerves that is induced by peripheral nerve injury is thought to contribute to the generation of "neuropathic" pain in humans. To examine the cellular mechanisms that underlie this activity, neurons in rat L(4)-L(5) dorsal root ganglion (DRG) were first grouped as "large," "medium," or "small" on the basis of their size (input capacitance) and action potential (AP) shape. A fourth group of cells that exhibited a pronounced afterdepolarization (ADP) were defined as AD-cells. Whole cell recording was used to compare the properties of control neurons with those dissociated from rats in which the sciatic nerve had been sectioned ("axotomy" group) and with neurons from rats that exhibited self-mutilatory behavior in response to sciatic nerve section ("autotomy" group). Increases in excitability in all types of DRG neuron were seen within 2-7 wk of axotomy. Resting membrane potential (RMP) and the amplitude and duration of the afterhyperpolarization (AHP) that followed the AP were unaffected. Effects of axotomy were greatest in the small, putative nociceptive cells and least in the large cells. Moderate changes were seen in the medium and AD-cells. Compared to control neurons, axotomized neurons exhibited a higher frequency of evoked AP discharge in response to 500-ms depolarizing current injections; i.e., "gain" was increased and accommodation was decreased. The minimum current required to discharge an AP (rheobase) was reduced. There were significant increases in spike width in small cells and significant increases in spike height in small, medium, and AD-cells. The electrophysiological changes promoted by axotomy were intensified in animals that exhibited autotomy; spike height, and spike width were significantly greater than control for all cell types. Under our experimental conditions, spontaneous activity was never encountered in neurons dissociated from animals that exhibited autotomy. Thus changes in the electrical properties of cell bodies alone may not entirely account for injury-induced spontaneous activity in sensory nerves. The onset of autotomy coincided with alterations in the excitability of large, putative nonnociceptive, neurons. Thus large cells from the autotomy group were much more excitable than those from the axotomy group, whereas small cells from the autotomy group were only slightly more excitable. This is consistent with the hypothesis that the onset of autotomy is associated with changes in the properties of myelinated fibers. Changes in Ca2+ and K+ channel conductances that contribute to axotomy- and autotomy-induced changes in excitability are addressed in the accompanying paper.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».