Peripheral inflammation alters desensitization of substance P-evoked current in rat dorsal root ganglion neurons

Complement Receptor C3aR1 Contributes to Paclitaxel-Induced Peripheral Neuropathic Pain in Mice and Rats

Cancer chemotherapy-induced neuropathic pain is a devastating pain syndrome without effective therapies. We previously reported that rats deficient in complement C3, the central component of complement activation cascade, showed a reduced degree of paclitaxel-induced mechanical allodynia (PIMA), suggesting that complement is integrally involved in the pathogenesis of this model. However, the underlying mechanism was unclear. Complement activation leads to the production of C3a, which mediates inflammation through its receptor C3aR1. In this article, we report that the administration of paclitaxel induced a significantly higher expression level of C3aR1 on dorsal root ganglion (DRG) macrophages and expansion of these macrophages in DRGs in wild-type (WT) compared with in C3aR1 knockout (KO) mice. We also found that paclitaxel induced less severe PIMA, along with a reduced DRG expression of transient receptor potential channels of the vanilloid subtype 4 (TRPV4), an essential mediator for PIMA, in C3aR1 KO than in WT mice. Treating WT mice or rats with a C3aR1 antagonist markedly attenuated PIMA in association with downregulated DRG TRPV4 expression, reduced DRG macrophages expansion, suppressed DRG neuron hyperexcitability, and alleviated peripheral intraepidermal nerve fiber loss. Administration of C3aR1 antagonist to TRPV4 KO mice further protected them from PIMA. These results suggest that complement regulates PIMA development through C3aR1 to upregulate TRPV4 on DRG neurons and promote DRG macrophage expansion. Targeting C3aR1 could be a novel therapeutic approach to alleviate this debilitating pain syndrome.

Effects of acupuncture knife on inflammatory factors and pain in third lumbar vertebrae transverse process syndrome model rats

The aim of this paper was to explore the long-term effects and pain relief mechanism of acupuncture knife on third lumbar vertebrae (L₃) transverse process syndrome. Forty SD rats were randomized into control, model, electroacupuncture (EA), and acupuncture knife (AK) group. Except control rats, other rats were subjected to an operation to emulate L₃ transverse process syndrome. Fourteen days after the operation, EA and AK rats were given electroacupuncture and acupuncture knife treatments, respectively. Fifty-six days after the operation, enzyme-linked immunosorbent assay was used to measure substance P (SP), 5-hydroxytryptamine (5-HT), interleukin-1β (IL-1β), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β) in peripheral blood. The tail flick test was used to observe pain threshold. We found that rats with the simulation operation had significantly higher levels of SP, 5-HT, IL-1, IL-10, TNF-α, and TGF-β, while the AK rats had lower levels. In addition, the pain threshold of AK rats was similar to that of control rats. AK pretreatment could alleviate pain through modulating inflammatory response.

Co-expression patterns of cocaine- and amphetamine-regulated transcript (CART) with neuropeptides in dorsal root ganglia of the pig

In the present study the neuronal distribution of CART was evaluated immunohistochemically in porcine dorsal root ganglia (DRGs). In co-localization studies the co-expression patterns of CART with SP, CGRP, galanin, CALB and LENK were investigated by means of triple immunohistochemical stainings. In porcine DRGs, the expression of CART was found in approximately 5% of primary sensory neurons. The vast majority (ca. 95%) of CART-immunoreactive (IR) neurons were small and middle sized, and only 5% were categorized as large. CART-IR neurons additionally exhibiting the presence of SP/CGRP (ca. 12%), SP/CALB (ca. 12%), SP/LENK (ca. 5%) were found. The vast majority of CART-IR/CGRP-IR neurons did not display immunoreaction to SP (ca. 60%). Subclasses of CART-IR/LENK-IR/SP-negative (ca. 5%), as well as CART-IR/CALB-IR/SP-negative neurons (ca. 10%), were also visualized. In addition, CART-IR neurons with no immunoreactivities to any of the neuropeptides studied were also shown. In porcine DRGs none of the CART-IR neurons exhibited the presence of galanin. The results obtained in the study suggest that CART may functionally modulate the activity of the porcine primary sensory neurons. It is concluded that co-expression of CART with CGRP, SP, LENK and CALB in subsets of the pig L1-L6 DRGs neurons provide anatomical evidence for a CART role in pain processing.

PCR detects bands consistent with the expression of receptors associated with pruritus in canine dorsal root ganglia

BACKGROUND

Various mediators are involved in the induction of itch, i.e. pruritus; however, the in vivo pharmacology of pruritus seems to be different in distinct species, and little is known about receptors that are involved in the induction of itch in dogs. The species differences in the mediation of pruritus might be explained by species differences in receptor expression in the sensory nerves, including the dorsal root ganglia (DRG).

HYPOTHESIS/OBJECTIVES

The aim of the study was to analyse the expression of receptors for various mediators of pruritus in canine DRG.

METHODS

Dorsal root ganglia of 14 dogs, which were euthanized for reasons not related to this study, were analysed. Multiple DRG per dog were dissected and, after homogenization of the DRG tissues, total RNA was isolated, reverse transcribed to complementary DNA and amplified with custom-synthesized primers.

RESULTS

The following receptors were found in canine DRG: transient receptor potential cation channel subfamily V member 1, tachykinin receptor 1, Toll-like receptor 7, endothelin receptor type A, opioid receptors μ1 and κ1, histamine H1 -H4 receptors and the interleukin-31 receptor complex.

CONCLUSIONS AND CLINICAL IMPORTANCE

PCR analysis detected bands consistent with the expression of receptors associated with pruritus in canine DRG.

Pain‑relieving effect of a compound isolated from white peony root oral liquid on acute radiation‑induced esophagitis

Acute radiation‑induced esophagitis (ARIE) is a common complication of radiotherapy. The aim of this study was to clarify the molecular mechanism of pain relief by the compound of white peony root oral liquid (cWPROL) in ARIE. An animal model of ARIE was established and either cWPROL or a mixture of lidocaine, dexamethasone and gentamycin (mLDG) was administered. We indirectly observed rat symptoms of pain by recording the weight of food and the volume of water consumed by the rats, along with changes in body weight. Additionally, the expression levels of substance P (SP) in the esophageal tissues were detected by immunohistochemistry. It was demonstrated that cWPROL was able to release the pain of ARIE by decreasing the expression of SP; this may be one of the molecular mechanisms via which cWPROL induces pain relief.