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Kaneko T, Kuwaki T. The opposite roles of orexin neurons in pain and itch neural processing. Peptides 2023; 160:170928. [PMID: 36566840 DOI: 10.1016/j.peptides.2022.170928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 12/17/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022]
Abstract
Pain and itch are antagonistically regulated sensations; pain suppresses itch, and inhibition of pain enhances itch. Understanding the central neural circuit of antagonistic regulation between pain and itch is required to develop new therapeutics better to manage these two feelings in a clinical situation. However, evidence of the neural mechanism underlying the pain-itch interaction in the central nervous system (CNS) is still insufficient. To pave the way for this research area, our laboratory has focused on orexin (ORX) producing neurons in the hypothalamus, which is known as a master switch that induces various defense responses when animals face a stressful environment. This review article summarized the previous evidence and our latest findings to argue the neural regulation between pain and itch and the bidirectional roles of ORX neurons in processing these two sensations. i.e., pain relief and itch exacerbation. Further, we discussed the possible neural circuit mechanism for the opposite controlling of pain and itch by ORX neurons. Focusing on the roles of ORX neurons would provide a new perspective to understand the antagonistic regulation of pain and itch in CNS.
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Affiliation(s)
- Tatsuroh Kaneko
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan.
| | - Tomoyuki Kuwaki
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8544, Japan
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Li Y, Yang XY, Jin N, Zhen C, Zhu SY, Chu WY, Zhang HH, Xu AP, Wu J, Wang MY, Zheng C. Activation of M 3-AChR and IP 3/Ca 2+/PKC signaling pathways by pilocarpine increases glycine-induced currents in ventral horn neurons of the spinal cord. Neurosci Lett 2022; 782:136690. [PMID: 35598692 DOI: 10.1016/j.neulet.2022.136690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 05/14/2022] [Accepted: 05/16/2022] [Indexed: 02/05/2023]
Abstract
Our study aimed to determine the effects of pilocarpine and the mechanisms involving muscarinic acetylcholine receptors (mAChRs) on glycine receptors (GlyRs) in neurons of the spinal cord ventral horn. An enzymatic digestion combined with acute mechanical separation was applied to isolate neurons from the spinal cord ventral horn. Patch-clamp recording was then used to investigate the outcomes of pilocarpine. Our results indicate that pilocarpine increased the glycine currents in a concentration-dependent manner, which was blocked by the M3-AChR selective antagonists 4-DAMP and J104129. Pilocarpine also enhanced the glycine currents in nominally Ca2+-free extracellular solution. Conversely, the enhancement of glycine currents by pilocarpine disappeared when intracellular Ca2+ was chelated by BAPTA. Heparin and Xe-C, which are IP3 receptor antagonists, also totally abolished the pilocarpine effect. Furthermore, Bis-IV, a PKC inhibitor, eliminated the pilocarpine effect. Additionally, PMA, a PKC activator, mimicked the pilocarpine effect. These results indicate that pilocarpine may increase the glycine currents by activating the M3-AChRs and IP3/Ca2+/PKC pathways.
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Affiliation(s)
- Yan Li
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Xin-Yu Yang
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Na Jin
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Cheng Zhen
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Su-Yue Zhu
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Wan-Yu Chu
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China; Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Huan-Huan Zhang
- Psychophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Ai-Ping Xu
- Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Jie Wu
- Laboratory of Brain Function and Diseases, Shantou University Medical College, Shantou, Guangdong 515041, China
| | - Meng-Ya Wang
- Cell Electrophysiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
| | - Chao Zheng
- Neurobiology Laboratory, Wannan Medical College, Wuhu, Anhui 241002, China
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