Role of Peripheral Peptidergic Fibers in Pain Sensation and Paw Volume During Inflammatory Arthriris in Male Wistar Rats
Journal Title: The 1st Annual Meeting of Georgian Center for Neuroscience Research - Year 2020, Vol 2, Issue 20
Abstract
Introduction: The peripheral nervous system contains primary sensory afferent C- & Aδ-fibers. They have vitally important role in pain signaling. C-fibers transmit poorly-localized or “slow pain” and Aδ-fibers mediates welllocalized or “fast pain”. C- and Aδ-fibers are different in terms of structure, mediator secretion, and surface receptor expression. In these cells, neuropeptides coexist with neurotransmitters. As we know, majority of C-fibers are peptidergic but less of Aδ-fibers are so. The aim of this study was to determine the role of peptidergic fibers in hyperalgesia, allodynia, and paw volume during Complete Freund’s Adjuvant (CFA)-induced arthritis in male wistar rats. Methods: Resiniferatoxin (RTX), a TRPV1 potent agonist, was used to study the role of C-fibers in chronic Pain. An i.p. injection of 200 µg/kg of RTX administered. Arthritis was induced by a single dose Injection of CFA to hindpaw. A diverse range of devices including radiant heat, vonFrey filaments, and plethysmometer were used to assess paw withdrawal latency (PWL), allodynia (PWT), and paw volume, respectively. Results: It showed that RTX treatment tends to increase in PWL 5 weeks after treatment but made no difference in allodynia. CFA injection tends to significant decrease in PWL in days 7, 14, and 21 and significant increase in allodynia in days 7 and 14. CFA injection following RTX treatment results in remarkable decrease in PWL in days 7, 14, and 21. Peak of hyperalgesia in CFA group was in day 14, and in RTX+CFA group was in day 7. There were also significant differences in PWL in days 7 and 14 between CFA and RTX+CFA groups. Peak of allodynia in CFA group was in day 7 and in RTX+CFA group was in day 14. Significant difference in allodynia was seen between CFA and RTX+CFA group in day 14 and its severity was also enhanced. There were no difference in paw volume between CFA and RTX+CFA groups (data not shown). Conclusion: Peptidergic fibers elimination increases hyperalgesia in otherwise normal rats. Inducing arthritis in previously RTX-treated rats results in earlier occurrence of peak of hyperalgesia. It may be due to decrement of Cfibers that are usually responsible for “slow pain”. The reason behind “no change in allodynia” in RTX-treated rats is consistent with previous studies that showed non-peptidergic nociceptors are essential for allodynia. However, the reason for later and more severe occurrence in peak of allodynia in RTX+CFA group might be due to that the existence of C-fibers in collaboration with Aδ-fibers is necessary for establishing allodynia, and on the other hand some degree of inhibition may be exerted on non-peptidergic fibers by C-fibers.
Authors and Affiliations
Sasan Gazerani, Jalal Zaringhalam
Keywords
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- EP ID EP677941
- DOI 10.29088/GCNR-2020.32
- Views 187
- Downloads 0
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