1. Reassessment of capsaicin desensitization in the rodent spinal dorsal horn.
- Author
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Shao C, Zhou WQ, Jia HY, Li G, Ma Y, Zhao M, Wu H, Yang K, Qian X, and Zhang MM
- Subjects
- Animals, Male, Rats, TRPV Cation Channels metabolism, TRPV Cation Channels drug effects, Posterior Horn Cells drug effects, Posterior Horn Cells metabolism, Capsaicin pharmacology, Spinal Cord Dorsal Horn drug effects, Spinal Cord Dorsal Horn metabolism, Rats, Sprague-Dawley, Glutamic Acid metabolism
- Abstract
Capsaicin activates primary afferent transient receptor potential vanilloid 1 (TRPV1) in the spinal dorsal horn and induces exaggerated glutamate release. This capsaicin action is followed by a lasting refractory state referred to as "capsaicin desensitization", which is considered a presynaptic event. In this study, using whole-cell recordings and holographic photostimulation, we reassessed this notion by investigating presynaptic glutamate release and the postsynaptic glutamate response during capsaicin administration. We found that both presynaptic synchronous glutamate release and the postsynaptic glutamate response were largely attenuated in this refractory state; in contrast, asynchronous release was exaggerated. Further behavioral studies revealed a quick increase in the mechanical pain threshold with intrathecal capsaicin administration. Taken together, both presynaptic synchronous glutamate release and the postsynaptic response are downregulated during capsaicin desensitization, and this desensitization may transiently increase the pain threshold. Since both presynaptic synchronous release and postsynaptic glutamate responses are attenuated, the traditional electrophysiological evidence supporting capsaicin desensitization as a presynaptic event should be reassessed., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)
- Published
- 2024
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