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Nguyen HTT, Cho DH, Jang SH, Han SK, Park SJ. Potentiation of the glycine response by serotonin on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis in mice. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2019; 23:271-279. [PMID: 31297011 PMCID: PMC6609265 DOI: 10.4196/kjpp.2019.23.4.271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/05/2019] [Accepted: 06/07/2019] [Indexed: 01/06/2023]
Abstract
The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (IGly). Firstly, we examined with a 5-HT1 receptor agonist (8-OH-DPAT, 5-HT1/7 agonist, co-applied with SB-269970, 5-HT7 antagonist) and antagonist (WAY-100635), but 5-HT1 receptor agonist did not increase IGly and in the presence of 5-HT1 antagonist, the potentiation of 5-HT on IGly still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT2 receptor mimicked and inhibited the enhancing effect of 5-HT on IGly in the SG neurons, respectively. We also verified the role of the 5-HT7 receptor by using a 5-HT7 antagonist (SB-269970) but it also did not block the enhancement of 5-HT on IGly. Our study demonstrated that 5-HT facilitated IGly in the SG neurons of the Vc through the 5-HT2 receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.
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Affiliation(s)
- Hoang Thi Thanh Nguyen
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
| | - Dong Hyu Cho
- Department of Obstetrics and Gynecology, Chonbuk National University Hospital and School of Medicine, Jeonju 54896, Korea
| | - Seon Hui Jang
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
| | - Soo Joung Park
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
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Sánchez-Brualla I, Boulenguez P, Brocard C, Liabeuf S, Viallat-Lieutaud A, Navarro X, Udina E, Brocard F. Activation of 5-HT 2A Receptors Restores KCC2 Function and Reduces Neuropathic Pain after Spinal Cord Injury. Neuroscience 2018; 387:48-57. [PMID: 28844001 DOI: 10.1016/j.neuroscience.2017.08.033] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/26/2017] [Accepted: 08/14/2017] [Indexed: 11/30/2022]
Abstract
Downregulation of the potassium chloride cotransporter type 2 (KCC2) after a spinal cord injury (SCI) disinhibits motoneurons and dorsal horn interneurons causing spasticity and neuropathic pain, respectively. We showed recently (Bos et al., 2013) that specific activation of 5-HT2A receptors by TCB-2 [(4-bromo-3,6-dimethoxybenzocyclobuten-1-yl)methylamine hydrobromide] upregulates KCC2 function, restores motoneuronal inhibition and reduces SCI-induced spasticity. Here, we tested the potential analgesic effect of TCB-2 on central (thoracic hemisection) and peripheral [spared nerve injury (SNI)] neuropathic pain. We found mechanical and thermal hyperalgesia reduced by an acute administration of TCB-2 in rats with SCI. This analgesic effect was associated with an increase in dorsal horn membrane KCC2 expression and was prevented by pharmacological blockade of KCC2 with an intrathecal injection of DIOA [(dihydroindenyl)oxy]alkanoic acid]. In contrast, the SNI-induced neuropathic pain was not attenuated by TCB-2 although there was a slight increase of membrane KCC2 expression in the dorsal horn ipsilateral to the lesion. Up-regulation of KCC2 function by targeting 5-HT2A receptors, therefore, has therapeutic potential in the treatment of neuropathic pain induced by SCI but not by SNI.
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Affiliation(s)
- Irene Sánchez-Brualla
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France; Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Pascale Boulenguez
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France
| | - Cécile Brocard
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France
| | - Sylvie Liabeuf
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France
| | - Annelise Viallat-Lieutaud
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France
| | - Xavier Navarro
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Esther Udina
- Department of Cell Biology, Physiology, and Immunology, Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas, Institute of Neurosciences, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Frédéric Brocard
- Team P3M, Institut de Neurosciences de la Timone, UMR7289, Aix Marseille Université and Centre National de la Recherche Scientifique (CNRS), Marseille, France.
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Activation of the Mammalian Target of Rapamycin in the Rostral Ventromedial Medulla Contributes to the Maintenance of Nerve Injury-Induced Neuropathic Pain in Rat. Neural Plast 2015; 2015:394820. [PMID: 26770837 PMCID: PMC4684879 DOI: 10.1155/2015/394820] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/06/2015] [Indexed: 11/20/2022] Open
Abstract
The mammalian target of rapamycin (mTOR), a serine-threonine protein kinase, integrates extracellular signals, thereby modulating several physiological and pathological processes, including pain. Previous studies have suggested that rapamycin (an mTOR inhibitor) can attenuate nociceptive behaviors in many pain models, most likely at the spinal cord level. However, the mechanisms of mTOR at the supraspinal level, particularly at the level of the rostral ventromedial medulla (RVM), remain unclear. Thus, the aim of this study was to elucidate the role of mTOR in the RVM, a key relay region for the descending pain control pathway, under neuropathic pain conditions. Phosphorylated mTOR was mainly expressed in serotonergic spinally projecting neurons and was significantly increased in the RVM after spared nerve injury- (SNI-) induced neuropathic pain. Moreover, in SNI rat brain slices, rapamycin infusion both decreased the amplitude instead of the frequency of spontaneous excitatory postsynaptic currents and reduced the numbers of action potentials in serotonergic neurons. Finally, intra-RVM microinjection of rapamycin effectively alleviated established mechanical allodynia but failed to affect the development of neuropathic pain. In conclusion, our data provide strong evidence for the role of mTOR in the RVM in nerve injury-induced neuropathic pain, indicating a novel mechanism of mTOR inhibitor-induced analgesia.
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Wang J, Zhang H, Feng YP, Meng H, Wu LP, Wang W, Li H, Zhang T, Zhang JS, Li YQ. Morphological evidence for a neurotensinergic periaqueductal gray-rostral ventromedial medulla-spinal dorsal horn descending pathway in rat. Front Neuroanat 2014; 8:112. [PMID: 25346662 PMCID: PMC4191475 DOI: 10.3389/fnana.2014.00112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/22/2014] [Indexed: 01/03/2023] Open
Abstract
Neurotensin (NT) is an endogenous neuropeptide that exerts potent opioid-independent analgesic effects, most likely via the type 2 NT receptor (NTR2). Previous morphological and electrophysiological studies suggested that the NT-NTR2 system is primarily localized in structures that constitute the descending pain control pathway, such as the periaqueductal gray (PAG), the rostral ventromedial medulla (RVM), and the spinal dorsal horn (SDH). However, relevant morphological evidence for this neurotensinergic (NTergic) circuit is lacking. Thus, the aim of the present study was to morphologically elucidate the potential sites and connections in the NT-NTR2 system that are involved in the descending pain control pathway. Based on light and electron microscopy combined with anterograde and retrograde tracing, we found evidence that NTR2-immunoreactive (IR) neurons in the RVM receive NT-IR projections originating from the PAG; express NT, serotonin (5-HT), or both; and send projections that terminate in laminae I and II of the SDH. These results suggest that NTR2 may contribute to pain control by binding to NT in the PAG-RVM-SDH pathway. In conclusion, our data provide morphological evidence for an NTergic PAG-RVM-SDH pathway, implicating novel mechanisms of NT-induced analgesia.
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Affiliation(s)
- Jian Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hua Zhang
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Yu-Peng Feng
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hua Meng
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Li-Ping Wu
- Department of Geriatrics, Xijing Hospital, The Fourth Military Medical University Xi'an, China
| | - Wen Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Hui Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Ting Zhang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Jin-Shan Zhang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University Xi'an, China
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Xie DJ, Uta D, Feng PY, Wakita M, Shin MC, Furue H, Yoshimura M. Identification of 5-HT receptor subtypes enhancing inhibitory transmission in the rat spinal dorsal horn in vitro. Mol Pain 2012; 8:58. [PMID: 22906126 PMCID: PMC3495670 DOI: 10.1186/1744-8069-8-58] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 04/27/2012] [Indexed: 12/15/2022] Open
Abstract
Background 5-hydroxytryptamine (5-HT) is one of the major neurotransmitters widely distributed in the CNS. Several 5-HT receptor subtypes have been identified in the spinal dorsal horn which act on both pre- and postsynaptic sites of excitatory and inhibitory neurons. However, the receptor subtypes and sites of actions as well as underlying mechanism are not clarified rigorously. Several electrophysiological studies have been performed to investigate the effects of 5-HT on excitatory transmission in substantia gelatinosa (SG) of the spinal cord. In the present study, to understand the effects of 5-HT on the inhibitory synaptic transmission and to identify receptor subtypes, the blind whole cell recordings were performed from SG neurons of rat spinal cord slices. Results Bath applied 5-HT (50 μM) increased the frequency but not amplitudes of spontaneous inhibitory postsynaptic currents (sIPSCs) in 58% of neurons, and both amplitude and frequency in 23% of neurons. The frequencies of GABAergic and glycinergic mIPSCs were both enhanced. TTX (0.5 μM) had no effect on the increasing frequency, while the enhancement of amplitude of IPSCs was eliminated. Evoked-IPSCs (eIPSCs) induced by focal stimulation near the recording neurons in the presence of CNQX and APV were enhanced in amplitude by 5-HT. In the presence of Ba2+ (1 mM), a potassium channel blocker, 5-HT had no effect on both frequency and amplitude. A 5-HT2A receptor agonist, TCB-2 mimicked the 5-HT effect, and ketanserin, an antagonist of 5-HT2A receptor, inhibited the effect of 5-HT partially and TCB-2 almost completely. A 5-HT2C receptor agonist WAY 161503 mimicked the 5-HT effect and this effect was blocked by a 5-HT2C receptor antagonist, N-desmethylclozapine. The amplitudes of sIPSCs were unaffected by 5-HT2A or 5-HT2C agonists. A 5-HT3 receptor agonist mCPBG enhanced both amplitude and frequency of sIPSCs. This effect was blocked by a 5-HT3 receptor antagonist ICS-205,930. The perfusion of 5-HT2B receptor agonist had no effect on sIPSCs. Conclusions Our results demonstrated that 5-HT modulated the inhibitory transmission in SG by the activation of 5-HT2A and 5-HT2C receptors subtypes located predominantly at inhibitory interneuron terminals, and 5-HT3 receptors located at inhibitory interneuron terminals and soma-dendrites, consequently enhanced both frequency and amplitude of IPSCs.
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Affiliation(s)
- Du-Jie Xie
- Graduate School of Health Sciences, Kumamoto Health Science University, Kumamoto 861-5598, Japan
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6
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Qi J, Zhang H, Guo J, Yang L, Wang W, Chen T, Li H, Wu SX, Li YQ. Synaptic connections of the neurokinin 1 receptor-like immunoreactive neurons in the rat medullary dorsal horn. PLoS One 2011; 6:e23275. [PMID: 21858052 PMCID: PMC3157358 DOI: 10.1371/journal.pone.0023275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 07/10/2011] [Indexed: 01/17/2023] Open
Abstract
The synaptic connections between neurokinin 1 (NK1) receptor-like immunoreactive (LI) neurons and γ-aminobutyric acid (GABA)-, glycine (Gly)-, serotonin (5-HT)- or dopamine-β-hydroxylase (DBH, a specific marker for norepinephrinergic neuronal structures)-LI axon terminals in the rat medullary dorsal horn (MDH) were examined under electron microscope by using a pre-embedding immunohistochemical double-staining technique. NK1 receptor-LI neurons were observed principally in laminae I and III, only a few of them were found in lamina II of the MDH. GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were densely encountered in laminae I and II, and sparsely in lamina III of the MDH. Some of these GABA-, Gly-, 5-HT-, or DBH-LI axon terminals were observed to make principally symmetric synapses with NK1 receptor-LI neuronal cell bodies and dendritic processes in laminae I, II and III of the MDH. The present results suggest that neurons expressing NK1 receptor within the MDH might be modulated by GABAergic and glycinergic inhibitory intrinsic neurons located in the MDH and 5-HT- or norepinephrine (NE)-containing descending fibers originated from structures in the brainstem.
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Affiliation(s)
- Jian Qi
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Hua Zhang
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Jun Guo
- Department of Physiology, The Fourth Military Medical University, Xi'an, China
| | - Le Yang
- Undergraduate Student of the 2007 in Pharmacology, The Fourth Military Medical University, Xi'an, China
| | - Wen Wang
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Tao Chen
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Hui Li
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Sheng-Xi Wu
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
| | - Yun-Qing Li
- Department of Anatomy and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, China
- * E-mail:
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7
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Abstract
Hyperalgesia and allodynia are frequent symptoms of disease and may be useful adaptations to protect vulnerable tissues. Both may, however, also emerge as diseases in their own right. Considerable progress has been made in developing clinically relevant animal models for identifying the most significant underlying mechanisms. This review deals with experimental models that are currently used to measure (sect. II) or to induce (sect. III) hyperalgesia and allodynia in animals. Induction and expression of hyperalgesia and allodynia are context sensitive. This is discussed in section IV. Neuronal and nonneuronal cell populations have been identified that are indispensable for the induction and/or the expression of hyperalgesia and allodynia as summarized in section V. This review focuses on highly topical spinal mechanisms of hyperalgesia and allodynia including intrinsic and synaptic plasticity, the modulation of inhibitory control (sect. VI), and neuroimmune interactions (sect. VII). The scientific use of language improves also in the field of pain research. Refined definitions of some technical terms including the new definitions of hyperalgesia and allodynia by the International Association for the Study of Pain are illustrated and annotated in section I.
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Affiliation(s)
- Jürgen Sandkühler
- Department of Neurophysiology, Center for Brain Research, Medical University of Vienna, Vienna, Austria
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8
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Gordon IT, Whelan PJ. Monoaminergic control of cauda-equina-evoked locomotion in the neonatal mouse spinal cord. J Neurophysiol 2006; 96:3122-9. [PMID: 16956991 DOI: 10.1152/jn.00606.2006] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Monoaminergic projections are among the first supraspinal inputs to innervate spinal networks. Little is known regarding the role of monoamines in modulating ongoing locomotor patterns evoked by endogenous release of neurotransmitter. Here we activate a locomotor-like rhythm by electrical stimulation of afferents and then test the modulatory effects of monoamines on the frequency, pattern, and quality of the rhythm. Stimulation of the cauda equina induced a rhythm consisting of left-right and ipsilateral alternation indicative of locomotor-like activity. First, we examined the effects of noradrenaline (NA), serotonin (5-HT), or dopamine (DA) at dose levels that did not elicit locomotor activity. Bath application of NA and DA resulted in a depression of the cauda-equina-evoked rhythm. Conversely, bath-applied 5-HT increased both the amplitude and cycle period of the evoked rhythm, an effect that was mimicked by the addition of 5-HT(2) agonists to the bath. Application of 5-HT(7) agonists disrupted the evoked rhythmic behavior. Next, we examined the effects of NA alpha(1) and alpha(2) agonists and found that the suppressive effects of NA on the rhythm could be reproduced by adding the alpha(2) agonist, clonidine, to the bath. In contrast, bath applying the alpha(1) agonist, phenylephrine, increased the amplitude and duration of the cycle period. Finally, the suppressive effects of DA were not replicated by the administration of D(1), D(2), or D(3) agonists although application of NA alpha(2) antagonists reversed the effects of DA. Application of D(1) agonists, increased the amplitude of the bursts but did not affect the cycle period. Our results indicate that monoamines can control the expression, pattern, and timing of cauda-equina-evoked locomotor patterns in developing mice.
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Affiliation(s)
- Ian T Gordon
- HSC 2119, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta T2N4N1, Canada
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Theiss RD, Heckman CJ. Systematic variation in effects of serotonin and norepinephrine on repetitive firing properties of ventral horn neurons. Neuroscience 2005; 134:803-15. [PMID: 15987664 DOI: 10.1016/j.neuroscience.2005.04.041] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 04/11/2005] [Accepted: 04/15/2005] [Indexed: 01/26/2023]
Abstract
Spinal interneurons are essential integrators of descending and peripheral input that receive profuse monoaminergic influence from brainstem nuclei. In this study, the effects of the monoamines serotonin and norepinephrine on the intrinsic properties of ventral horn interneurons were investigated in a slice preparation of the lumbar cord of 7-19 day old rats. Three cell groups with distinct firing patterns in response to steps of injected current were observed and classified as repetitive-firing, initial-burst or single-spiking. Input conductance tended to be largest in single-spiking cells whereas repetitive-firing cells showed the greatest tendency for spontaneous firing and had the fastest rate of rise for the action potential. Rhythmic firing behaviors were defined by the frequency-current relation evoked by linearly increasing current ramps. The monoaminergic modulation of firing patterns and frequency-current relations was primarily studied in repetitive-firing cells. The frequency-current threshold current was decreased in cells with high pre-drug values and increased in cells with low pre-drug values. Therefore, monoamine administration decreased the input-output heterogeneity of the repetitive-firing cells by compressing the range of frequency-current threshold currents. This action of monoamines may have a key role in the suppression of sensory-evoked reflexes and the production of coordinated movement.
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Affiliation(s)
- R D Theiss
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 East Chicago Avenue, Chicago, IL 60611, USA
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Pearlstein E, Ben Mabrouk F, Pflieger JF, Vinay L. Serotonin refines the locomotor-related alternations in thein vitroneonatal rat spinal cord. Eur J Neurosci 2005; 21:1338-46. [PMID: 15813943 DOI: 10.1111/j.1460-9568.2005.03971.x] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Serotonergic projections from raphe nuclei arrive in the lumbar enlargement of the spinal cord during the late fetal period in the rat, a time window during which the locomotor-related left/right and flexor/extensor coordinations switch from synchrony to alternation. The goal of the present study was to investigate the role played by serotonin (5-HT) in modulating the left/right and flexor/extensor alternations. Fictive locomotion was induced by bath application of N-methyl-D,L-aspartate (NMA) in the in vitro neonatal rat spinal cord preparation. By means of cross-correlation analysis we demonstrate that 5-HT, when added to NMA, improves left/right and flexor/extensor (recorded from the 3rd and 5th lumbar ventral roots, respectively) alternations. This effect was partly reproduced by activation of 5-HT(2A/2C) receptors. We then tested the contribution of endogenous 5-HT to NMA-induced fictive locomotion. Reducing the functional importance of endogenous 5-HT, either by inhibiting its synthesis with daily injections of p-chloro-phenylalanine (PCPA), starting on the day of birth, or by application of ketanserin (a 5-HT(2) receptor antagonist) or SB269970 (a 5-HT(7) receptor antagonist), disorganized the NMA-induced locomotor pattern. This pattern was restored in PCPA-treated animals by adding 5-HT to the bath. Blocking 5-HT(7) receptors disorganized the locomotor-like rhythm even in the absence of electrical activity in the brain stem, suggesting that NMA applied to the spinal cord does not cause 5-HT release by activating a spino-raphe-spinal loop. These results demonstrate that 5-HT is critical in improving the locomotor-related alternations in the neonatal rat.
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Affiliation(s)
- E Pearlstein
- Laboratoire Plasticité et Physio-Pathologie de la Motricité (PM), CNRS & Université de la Méditerranée, UMR 6196, CNRS, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France.
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11
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Li H, Wu L, Li YQ. Adenosine suppresses GABAA receptor-mediated responses in rat sacral dorsal commissural neurons. Auton Neurosci 2004; 111:71-9. [PMID: 15182736 DOI: 10.1016/j.autneu.2004.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Revised: 01/15/2004] [Accepted: 01/16/2004] [Indexed: 12/11/2022]
Abstract
The modulatory effect of adenosine on gamma-aminobutyric acid (GABA)-activated whole-cell currents were investigated in the neurons acutely dissociated from the rat sacral dorsal commissural nucleus (SDCN) using the nystatin perforated patch recording configuration under the voltage-clamp conditions. The results showed that: (1) GABA acted on GABAA receptor and elicited inward Cl- currents (IGABA) at a holding potential (VH) of -40 mV; (2) adenosine suppressed GABA-induced Cl- current without affecting the reversal potential of IGABA and the apparent affinity of GABA to its receptor; (3) N6-cyclohexyladenosine mimicked the suppression effect of adenosine on IGABA, whereas 8-cyclopentyl-1,3-dipropylxanthine blocked the suppression effect of adenosine; (4) adenosine fails to suppress IGABA on the neurons that were pretreated with bisindolylmaleimide I (BIM), while after pretreatment with H-89, the inhibitory effect of adenosine on IGABA were not affected; (5) the suppression effect of adenosine on IGABA remained in the presence of BAPTA-AM. The present results indicate that the suppression of adenosine on IGABA is mediated by adenosine A1 receptor and through a Ca2+-independent protein kinase C transduction pathway, and that the interactions between adenosine and GABA might participate in the modulation of nociceptive information transmission at the SDCN.
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Affiliation(s)
- Hui Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, No. 17, W. Chang-le Road, Xi'an 710032, PR China
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12
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Doly S, Madeira A, Fischer J, Brisorgueil MJ, Daval G, Bernard R, Vergé D, Conrath M. The 5-HT2A receptor is widely distributed in the rat spinal cord and mainly localized at the plasma membrane of postsynaptic neurons. J Comp Neurol 2004; 472:496-511. [PMID: 15065122 DOI: 10.1002/cne.20082] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Serotonin (5-HT) plays a major role at the spinal level by modulating most spinal functions through several receptor subtypes including the 5-HT2A receptor. To gain further insight into the cellular role of this receptor, we performed an immunocytochemical study of 5-HT2A receptors in the rat spinal cord, at light and electron microscope levels. The results showed that 5-HT2A receptors were widely distributed in the spinal cord at all segmental levels. Immunolabeling was particularly dense in lamina IX and in the dorsal horn lamina IIi. Immunoreactive cell bodies were numerous in lamina IX, where many but not all motoneurons were labeled, as shown by double labeling with choline acetyltransferase antibodies. Stained cell bodies were also observed in the gray matter. The study at the ultrastructural level focused on the lumbar dorsal horn (laminae I-II) and ventral horn (lamina IX). At both levels, 5-HT2A immunoreactivity was mainly postsynaptic on dendrites and cell bodies. However, a little presynaptic labeling was also observed in axon and axon terminals, some of them containing large granular vesicles attesting to their peptidergic nature. The main result of our study was the "nonsynaptic" plasma membrane localization of 5-HT2A receptors covering a large surface of cell bodies and dendrites, suggesting a paracrine form of action of serotonin. These observations are consistent with a double role (pre- and postsynaptic) for serotonin on these receptors on various cellular targets.
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Affiliation(s)
- Stéphane Doly
- Neurobiologie des Signaux Intercellulaires, Centre National de la Recherche Scientifique UMR 7101, Université Pierre et Marie Curie, 7 Quai Saint Bernard, 75252 Paris cedex 05, France.
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Wang YY, Wu SX, Liu XY, Wang W, Li YQ. Effects of c-fos antisense oligodeoxynucleotide on 5-HT-induced upregulation of preprodynorphin, preproenkephalin, and glutamic acid decarboxylase mRNA expression in cultured rat spinal dorsal horn neurons. Biochem Biophys Res Commun 2003; 309:631-6. [PMID: 12963037 DOI: 10.1016/j.bbrc.2003.08.046] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Effects of c-fos antisense oligodeoxynucleotide (ASO) on serotonin (5-HT)-induced upregulation of preprodynorphin (ppDyn), preproenkephalin (ppEnk), and glutamic acid decarboxylase (GAD), a special chemical marker for gamma-aminobutyric acid (GABA) neurons, mRNAs in cultured spinal dorsal horn neurons were investigated in order to extend our understanding of expressions of opioid peptides and GABA in spinal cord regulated by the descending serotonergic efferents. Reverse transcription-polymerase chain reaction analysis revealed a time-course increase in the expression of mRNAs encoding c-fos, ppDyn, ppEnk, and GAD after administration of 5-HT (100 nM). Administration of c-fos ASO (0.02 nM) 30 min prior to 5-HT application markedly blocked the expression of c-fos gene. Moreover, c-fos ASO pretreatment significantly decreased the 5-HT-induced upregulation of ppDyn and ppEnk mRNAs, but failed to affect the expression level of GAD mRNA. These results suggest that the serotoningic raphe-spinal efferents might play an important role in regulating the synthesis of enkephalin, dynorphin, and GABA in the spinal dorsal horn neurons. The immediate early oncogene c-fos might be involved in the 5-HT-induced increase in ppDyn and ppEnk expression. However, under the present experimental conditions, c-fos does not seem to be associated with the upregulation of GAD mRNA induced by 5-HT.
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Affiliation(s)
- Y-Y Wang
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, People's Republic of China
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Li H, Wu L, Li YQ. Opioid peptides modulate the response of neurons of the superficial laminae of the rat spinal dorsal horn to GABA. Biochem Biophys Res Commun 2003; 307:730-6. [PMID: 12893284 DOI: 10.1016/s0006-291x(03)01249-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The modulatory effects of methionine-enkephalin (M-ENK) and selective opioid-receptor agonists on GABA-activated whole-cell currents were investigated in neurons acutely dissociated from the superficial laminae of the rat spinal dorsal horn using nystatin-perforated patch recording configuration under voltage-clamp conditions. The results show that: (1). GABA acted on GABA(A) receptors and elicited inward Cl(-) currents (I(GABA)) at -60 mV; (2). M-ENK depressed I(GABA) in approximately 65% of the tested neurons and potentiated I(GABA) in approximately 15% of the neurons tested; (3). the agonists of mu-, kappa-, and delta-opioid receptors-[D-AIa(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO), dynorphin-A (Dyn-A), and [D-Pen(2),D-Pen(5)]-enkephalin (DPDPE) also depressed the I(GABA), and the order of agonist potency was DAMGO>Dyn-A>DPDPE; and (4) naloxone blocked the inhibitory effects of M-ENK on I(GABA). The antagonists of mu-, kappa-, and delta-opioid receptors-beta-funaltrexamine (beta-FNA), nor-binaltorphimine (nor-BNI), and naltrindole (NTI) prevented the DAMGO-, Dyn-A-, and DPDPE-induced depression of I(GABA). The results suggest that M-ENK downregulates I(GABA) principally through mu- and kappa-opioid receptors, and thus exerts its modulating effects indirectly on the transmission of noxious information at the spinal level.
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Affiliation(s)
- Hui Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an 710032, China
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