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Lucas-Romero J, Rivera-Arconada I, Lopez-Garcia JA. Noise or signal? Spontaneous activity of dorsal horn neurons: patterns and function in health and disease. Pflugers Arch 2024:10.1007/s00424-024-02971-8. [PMID: 38822875 DOI: 10.1007/s00424-024-02971-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 04/10/2024] [Accepted: 05/05/2024] [Indexed: 06/03/2024]
Abstract
Spontaneous activity refers to the firing of action potentials by neurons in the absence of external stimulation. Initially considered an artifact or "noise" in the nervous system, it is now recognized as a potential feature of neural function. Spontaneous activity has been observed in various brain areas, in experimental preparations from different animal species, and in live animals and humans using non-invasive imaging techniques. In this review, we specifically focus on the spontaneous activity of dorsal horn neurons of the spinal cord. We use a historical perspective to set the basis for a novel classification of the different patterns of spontaneous activity exhibited by dorsal horn neurons. Then we examine the origins of this activity and propose a model circuit to explain how the activity is generated and transmitted to the dorsal horn. Finally, we discuss possible roles of this activity during development and during signal processing under physiological conditions and pain states. By analyzing recent studies on the spontaneous activity of dorsal horn neurons, we aim to shed light on its significance in sensory processing. Understanding the different patterns of activity, the origins of this activity, and the potential roles it may play, will contribute to our knowledge of sensory mechanisms, including pain, to facilitate the modeling of spinal circuits and hopefully to explore novel strategies for pain treatment.
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Affiliation(s)
- Javier Lucas-Romero
- Department of Systems Biology, University of Alcala, 28805, Madrid, Spain
- Department of Physical Therapy, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, 63108, USA
| | | | - Jose Antonio Lopez-Garcia
- Department of Systems Biology, University of Alcala, 28805, Madrid, Spain.
- Departamento de Biologia de Sistemas, Edificio de Medicina, Universidad de Alcala, Ctra. Madrid-Barcelona, Km 33,600, 28805, Alcala de Henares, Madrid, Spain.
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2
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Zheng Y, Jia C, Jiang X, Chen J, Chen XL, Ying X, Wu J, Jiang M, Yang G, Tu W, Zhou K, Jiang S. Electroacupuncture effects on the P2X4R pathway in microglia regulating the excitability of neurons in the substantia gelatinosa region of rats with spinal nerve ligation. Mol Med Rep 2021; 23:175. [PMID: 33398365 PMCID: PMC7821227 DOI: 10.3892/mmr.2020.11814] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 05/05/2020] [Indexed: 01/02/2023] Open
Abstract
Electroacupuncture (EA) has been used to treat neuropathic pain induced by peripheral nerve injury (PNI) by applying an electrical current to acupoints with acupuncture needles. However, the mechanisms by which EA treats pain remain indistinct. High P2X4 receptor (P2X4R) expression levels demonstrate a notable increase in hyperactive microglia in the ipsilateral spinal dorsal horn following PNI. In order to demonstrate the possibility that EA analgesia is mediated in part by P2X4R in hyperactive microglia, the present study performed mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests in male Sprague-Dawley rats that had undergone spinal nerve ligation (SNL). The expression levels of spinal P2X4R were determined using reverse transcription-quantitative PCR, western blotting analysis and immunofluorescence staining. Furthermore, spontaneous excitatory postsynaptic currents (sEPSCs) were recorded using whole-cell patch clamp to demonstrate the effect of EA on synaptic transmission in rat spinal substantia gelatinosa (SG) neurons. The results of the present study demonstrated that EA increased the MWT and TWL and decreased overexpression of P2X4R in hyperactive microglia in SNL rats. Moreover, EA attenuated the frequency of sEPSCs in SG neurons in SNL rats. The results of the present study indicate that EA may mediate P2X4R in hyperactive spinal microglia to inhibit nociceptive transmission of SG neurons, thus relieving pain in SNL rats.
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Affiliation(s)
- Yuyin Zheng
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Chengqian Jia
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Xia Jiang
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Jie Chen
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Xiao-Long Chen
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Xinwang Ying
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Jiayu Wu
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Mingchen Jiang
- China‑USA Institute for Acupuncture and Rehabilitation, Integrative and Optimized Medicine Research Center, Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Guanhu Yang
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Wenzhan Tu
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Kecheng Zhou
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
| | - Songhe Jiang
- Department of Physical Medicine and Rehabilitation, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang 325027, P.R. China
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3
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He JT, Li XY, Zhao X, Liu X. Hyperpolarization-activated and cyclic nucleotide-gated channel proteins as emerging new targets in neuropathic pain. Rev Neurosci 2019; 30:639-649. [PMID: 30768426 DOI: 10.1515/revneuro-2018-0094] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 10/26/2018] [Indexed: 01/14/2023]
Abstract
Abstract
Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are activated during hyperpolarization, and there is an inward flow of current, which is termed as hyperpolarization-activated current, Ih. Initially, these channels were identified on the pacemaker cells of the heart. Nowadays, these are identified on different regions of the nervous system, including peripheral nerves, dorsal root ganglia, dorsal horns, and different parts of the brain. There are four different types of HCN channels (HCN1–HCN4); however, HCN1 and HCN2 are more prominent. A large number of studies have shown that peripheral nerve injury increases the amplitude of Ih current in the neurons of the spinal cord and the brain. Moreover, there is an increase in the expression of HCN1 and HCN2 protein channels in peripheral axons and the spinal cord and brain regions in experimental models of nerve injury. Studies have also documented the pain-attenuating actions of selective HCN inhibitors, such as ivabradine and ZD7288. Moreover, certain drugs with additional HCN-blocking activities have also shown pain-attenuating actions in different pain models. There have been few studies documenting the relationship of HCN channels with other mediators of pain. Nevertheless, it may be proposed that the HCN channel activity is modulated by endogenous opioids and cyclo-oxygenase-2, whereas the activation of these channels may modulate the actions of substance P and the expression of spinal N-methyl-D-aspartate receptor subunit 2B to modulate pain. The present review describes the role and mechanisms of HCN ion channels in the development of neuropathic pain.
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Affiliation(s)
- Jin-Ting He
- Department of Neurology , China-Japan Union Hospital, Jilin University , Changchun 130033, Jilin Province , China
| | - Xiao-Yan Li
- Department of Neurology , China-Japan Union Hospital, Jilin University , Changchun 130033, Jilin Province , China
| | - Xin Zhao
- Department of Paediatrics , The First Hospital of Jilin University , Changchun 130021, Jilin Province , China
| | - Xiaoliang Liu
- Cancer Center, The First Hospital of Jilin University , 126 Xiantai Street , Changchun 130033, Jilin Province , China
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Lucas-Romero J, Rivera-Arconada I, Roza C, Lopez-Garcia JA. Origin and classification of spontaneous discharges in mouse superficial dorsal horn neurons. Sci Rep 2018; 8:9735. [PMID: 29950700 PMCID: PMC6021406 DOI: 10.1038/s41598-018-27993-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 06/13/2018] [Indexed: 12/24/2022] Open
Abstract
Superficial laminae of the spinal cord possess a considerable number of neurons with spontaneous activity as reported in vivo and in vitro preparations of several species. Such neurons may play a role in the development of the nociceptive system and/or in the spinal coding of somatosensory signals. We have used electrophysiological techniques in a horizontal spinal cord slice preparation from adult mice to investigate how this activity is generated and what are the main patterns of activity that can be found. The results show the existence of neurons that fire regularly and irregularly. Within each of these main types, it was possible to distinguish patterns of spontaneous activity formed by single action potentials and different types of bursts according to intra-burst firing frequency. Activity in neurons with irregular patterns was blocked by a mixture of antagonists of the main neurotransmitter receptors present in the cord. Approximately 82% of neurons with a regular firing pattern were insensitive to synaptic antagonists but their activity was inhibited by specific ion channel blockers. It is suggested that these neurons generate endogenous activity due to the functional expression of hyperpolarisation-activated and persistent sodium currents driving the activity of irregular neurons.
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Affiliation(s)
- Javier Lucas-Romero
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Ivan Rivera-Arconada
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Carolina Roza
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Jose A Lopez-Garcia
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain.
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HCN2 ion channels: basic science opens up possibilities for therapeutic intervention in neuropathic pain. Biochem J 2016; 473:2717-36. [DOI: 10.1042/bcj20160287] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 05/18/2016] [Indexed: 01/22/2023]
Abstract
Nociception — the ability to detect painful stimuli — is an invaluable sense that warns against present or imminent damage. In patients with chronic pain, however, this warning signal persists in the absence of any genuine threat and affects all aspects of everyday life. Neuropathic pain, a form of chronic pain caused by damage to sensory nerves themselves, is dishearteningly refractory to drugs that may work in other types of pain and is a major unmet medical need begging for novel analgesics. Hyperpolarisation-activated cyclic nucleotide (HCN)-modulated ion channels are best known for their fundamental pacemaker role in the heart; here, we review data demonstrating that the HCN2 isoform acts in an analogous way as a ‘pacemaker for pain’, in that its activity in nociceptive neurons is critical for the maintenance of electrical activity and for the sensation of chronic pain in pathological pain states. Pharmacological block or genetic deletion of HCN2 in sensory neurons provides robust pain relief in a variety of animal models of inflammatory and neuropathic pain, without any effect on normal sensation of acute pain. We discuss the implications of these findings for our understanding of neuropathic pain pathogenesis, and we outline possible future opportunities for the development of efficacious and safe pharmacotherapies in a range of chronic pain syndromes.
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Liu N, Zhang D, Zhu M, Luo S, Liu T. Minocycline inhibits hyperpolarization-activated currents in rat substantia gelatinosa neurons. Neuropharmacology 2015; 95:110-20. [PMID: 25777286 DOI: 10.1016/j.neuropharm.2015.03.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 03/04/2015] [Accepted: 03/05/2015] [Indexed: 12/30/2022]
Abstract
Minocycline is a widely used glial activation inhibitor that could suppress pain-related behaviors in a number of different pain animal models, yet, its analgesic mechanisms are not fully understood. Hyperpolarization-activated cation channel-induced Ih current plays an important role in neuronal excitability and pathological pain. In this study, we investigated the possible effect of minocycline on Ih of substantia gelatinosa neuron in superficial spinal dorsal horn by using whole-cell patch-clamp recording. We found that extracellular minocycline rapidly decreases Ih amplitude in a reversible and concentration-dependent manner (IC50 = 41 μM). By contrast, intracellular minocycline had no effect. Minocycline-induced inhibition of Ih was not affected by Na(+) channel blocker tetrodotoxin, glutamate-receptor antagonists (CNQX and D-APV), GABAA receptor antagonist (bicuculine methiodide), or glycine receptor antagonist (strychnine). Minocycline also caused a negative shift in the activation curve of Ih, but did not alter the reversal potential. Moreover, minocycline slowed down the inter-spike depolarizing slope and produced a robust decrease in the rate of action potential firing. Together, these results illustrate a novel cellular mechanism underlying minocycline's analgesic effect by inhibiting Ih currents of spinal dorsal horn neurons.
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Affiliation(s)
- Nana Liu
- Department of Pediatrics, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Daying Zhang
- Department of Pain Clinic, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Mengye Zhu
- Department of Pain Clinic, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Shiwen Luo
- Center for Laboratory Medicine, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Tao Liu
- Department of Pediatrics, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China; Center for Laboratory Medicine, the First Affiliated Hospital of Nanchang University, Nanchang, 330006, China.
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Rivera-Arconada I, Lopez-Garcia JA. Characterisation of rebound depolarisation in mice deep dorsal horn neurons in vitro. Pflugers Arch 2014; 467:1985-96. [PMID: 25292284 DOI: 10.1007/s00424-014-1623-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/19/2014] [Accepted: 09/30/2014] [Indexed: 10/24/2022]
Abstract
Spinal dorsal horn neurons constitute the first relay for pain processing and participate in the processing of other sensory, motor and autonomic information. At the cellular level, intrinsic excitability is a factor contributing to network function. In turn, excitability is set by the array of ionic conductance expressed by neurons. Here, we set out to characterise rebound depolarisation following hyperpolarisation, a feature frequently described in dorsal horn neurons but never addressed in depth. To this end, an in vitro preparation of the spinal cord from mice pups was used combined with whole-cell recordings in current and voltage clamp modes. Results show the expression of H- and/or T-type currents in a significant proportion of dorsal horn neurons. The expression of these currents determines the presence of rebound behaviour at the end of hyperpolarising pulses. T-type calcium currents were associated to high-amplitude rebounds usually involving high-frequency action potential firing. H-currents were associated to low-amplitude rebounds less prone to elicit firing or firing at lower frequencies. For a large proportion of neurons expressing both currents, the H-current constitutes a mechanism to ensure a faster response after hyperpolarisations, adjusting the latency of the rebound firing. We conclude that rebound depolarisation and firing are intrinsic factors to many dorsal horn neurons that may constitute a mechanism to integrate somatosensory information in the spinal cord, allowing for a rapid switch from inhibited-to-excited states.
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Affiliation(s)
- Ivan Rivera-Arconada
- Department of Biología de Sistemas (Área Fisiología) Edificio de Medicina, Universidad de Alcala, 28871, Alcalá de Henares, Madrid, Spain
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Xia J, Pan R, Gao X, Meucci O, Hu H. Native store-operated calcium channels are functionally expressed in mouse spinal cord dorsal horn neurons and regulate resting calcium homeostasis. J Physiol 2014; 592:3443-61. [PMID: 24860175 DOI: 10.1113/jphysiol.2014.275065] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Store-operated calcium channels (SOCs) are calcium-selective cation channels that mediate calcium entry in many different cell types. Store-operated calcium entry (SOCE) is involved in various cellular functions. Increasing evidence suggests that impairment of SOCE is responsible for numerous disorders. A previous study demonstrated that YM-58483, a potent SOC inhibitor, strongly attenuates chronic pain by systemic or intrathecal injection and completely blocks the second phase of formalin-induced spontaneous nocifensive behaviour, suggesting a potential role of SOCs in central sensitization. However, the expression of SOCs, their molecular identity and function in spinal cord dorsal horn neurons remain elusive. Here, we demonstrate that SOCs are expressed in dorsal horn neurons. Depletion of calcium stores from the endoplasmic reticulum (ER) induced large sustained calcium entry, which was blocked by SOC inhibitors, but not by voltage-gated calcium channel blockers. Depletion of ER calcium stores activated inward calcium-selective currents, which was reduced by replacing Ca(2+) with Ba(2+) and reversed by SOC inhibitors. Using the small inhibitory RNA knockdown approach, we identified both STIM1 and STIM2 as important mediators of SOCE and SOC current, and Orai1 as a key component of the Ca(2+) release-activated Ca(2+) channels in dorsal horn neurons. Knockdown of STIM1, STIM2 or Orai1 decreased resting Ca(2+) levels. We also found that activation of neurokinin 1 receptors led to SOCE and activation of SOCs produced an excitatory action in dorsal horn neurons. Our findings reveal that a novel SOC signal is present in dorsal horn neurons and may play an important role in pain transmission.
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Affiliation(s)
- Jingsheng Xia
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, USA
| | - Rong Pan
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, USA
| | - Xinghua Gao
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, USA Department of Pharmacology of Chinese Materia Medica, China Pharmaceutical University, Nanjing, China
| | - Olimpia Meucci
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, USA
| | - Huijuan Hu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, USA
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Kodirov SA, Wehrmeister M, Colom LV. Modulation of HCN channels in lateral septum by nicotine. Neuropharmacology 2014; 81:274-82. [PMID: 24582613 DOI: 10.1016/j.neuropharm.2014.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Revised: 02/12/2014] [Accepted: 02/15/2014] [Indexed: 10/25/2022]
Abstract
The effects of addictive drugs most commonly occur via interactions with target receptors. The same is true of nicotine and its multiple receptors in a variety of cell types. However, there are also side effects for given substances that can dramatically change cellular, tissue, organ, and organism functions. In this study, we present evidence that nicotine possesses such properties, and modulates neuronal excitability. We recorded whole-cell voltages and currents in neurons situated in the dorsal portion of the lateral septum in acute coronal brain slices of adult rats. Our experiments in the lateral septum revealed that nicotine directly affects HCN - hyperpolarization-activated cyclic nucleotide gated non-selective cation channels. We demonstrate that nicotine effects persist despite the concurrent application of nicotinic acetylcholine receptors' antagonists - mecamylamine, methyllycaconitine, and dihydro-β-erythroidine. These results are novel in regard to HCN channels in the septum, in general, and in their sensitivity to nicotine, in particular.
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Affiliation(s)
- Sodikdjon A Kodirov
- Center for Biomedical Studies, Department of Biological Sciences, University of Texas at Brownsville, TX 78520, USA; Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA 52252, USA.
| | - Michael Wehrmeister
- Center for Biomedical Studies, Department of Biological Sciences, University of Texas at Brownsville, TX 78520, USA; Johannes Gutenberg University, 55099 Mainz, Germany
| | - Luis V Colom
- Center for Biomedical Studies, Department of Biological Sciences, University of Texas at Brownsville, TX 78520, USA
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