TRPV1型
瞬时受体电位通道
背根神经节
化学
阿片受体
(+)-纳洛酮
受体
药理学
类阿片
痛觉过敏
脂毒素
辣椒素
内分泌学
内科学
医学
生物
神经科学
伤害
感觉系统
生物化学
作者
Jeannette Endres-Becker,Paul A. Heppenstall,Shaaban A. Mousa,Dominika Łabuz,A. Oksche,Michael Schäfer,Christoph Stein,Christian Zöllner
出处
期刊:Molecular Pharmacology
[American Society for Pharmacology & Experimental Therapeutics]
日期:2006-09-27
卷期号:71 (1): 12-18
被引量:141
标识
DOI:10.1124/mol.106.026740
摘要
Current therapy for inflammatory pain includes the peripheral application of opioid receptor agonists. Activation of opioid receptors modulates voltage-gated ion channels, but it is unclear whether opioids can also influence ligand-gated ion channels [e.g., the transient receptor potential vanilloid type 1 (TRPV1)]. TRPV1 channels are involved in the development of thermal hypersensitivity associated with tissue inflammation. In this study, we investigated μ-opioid receptor and TRPV1 expression in primary afferent neurons in the dorsal root ganglion (DRG) in complete Freund9s adjuvant (CFA)-induced paw inflammation. In addition, the present study examined whether the activity of TRPV1 in DRG neurons can be inhibited by μ-opioid receptor (μ-receptor) ligands and whether this inhibition is increased after CFA inflammation. Immunohistochemistry demonstrated colocalization of TRPV1 and μ-receptors in DRG neurons. CFA-induced inflammation increased significantly the number of TRPV1- and μ-receptor-positive DRG neurons, as well as TRPV1 binding sites. In whole-cell patch clamp studies, opioids significantly decreased capsaicin-induced TRPV1 currents in a naloxone- and pertussis toxinsensitive manner. The inhibitory effect of morphine on TRPV1 was abolished by forskolin and 8-bromo-cAMP. During inflammation, an increase in TRPV1 is apparently rivaled by an increase of μ-receptors. However, in single dissociated DRG neurons, the inhibitory effects of morphine are not different between animals with and without CFA inflammation. In in vivo experiments, we found that locally applied morphine reduced capsaicin-induced thermal allodynia. In summary, our results indicate that μ-receptor activation can inhibit the activity of TRPV1 via Gi/o proteins and the cAMP pathway. These observations demonstrate an important new mechanism underlying the analgesic efficacy of peripherally acting μ-receptor ligands in inflammatory pain.
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