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Mahrous AA, Liang L, Balaguer JM, Ho JC, Hari K, Grigsby EM, Karapetyan V, Damiani A, Fields DP, Gonzalez-Martinez JA, Gerszten PC, Bennett DJ, Heckman CJ, Pirondini E, Capogrosso M. GABA Increases Sensory Transmission In Monkeys. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.28.573467. [PMID: 38234767 PMCID: PMC10793394 DOI: 10.1101/2023.12.28.573467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Sensory input flow is central to voluntary movements. For almost a century, GABA was believed to modulate this flow by inhibiting sensory axons in the spinal cord to sculpt neural inputs into skilled motor output. Instead, here we show that GABA can also facilitate sensory transmission in monkeys and consequently increase spinal and cortical neural responses to sensory inputs challenging our understanding of generation and perception of movement.
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2
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Metz K, Matos IC, Li Y, Afsharipour B, Thompson CK, Negro F, Quinlan KA, Bennett DJ, Gorassini MA. Facilitation of sensory transmission to motoneurons during cortical or sensory-evoked primary afferent depolarization (PAD) in humans. J Physiol 2023; 601:1897-1924. [PMID: 36916205 PMCID: PMC11037101 DOI: 10.1113/jp284275] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 03/09/2023] [Indexed: 03/16/2023] Open
Abstract
Sensory and corticospinal tract (CST) pathways activate spinal GABAergic interneurons that have axoaxonic connections onto proprioceptive (Ia) afferents that cause long-lasting depolarizations (termed primary afferent depolarization, PAD). In rodents, sensory-evoked PAD is produced by GABAA receptors at nodes of Ranvier in Ia afferents, rather than at presynaptic terminals, and facilitates spike propagation to motoneurons by preventing branch-point failures, rather than causing presynaptic inhibition. We examined in 40 human participants whether putative activation of Ia-PAD by sensory or CST pathways can also facilitate Ia afferent activation of motoneurons via the H-reflex. H-reflexes in several leg muscles were facilitated by prior conditioning from low-threshold proprioceptive, cutaneous or CST pathways, with a similar long-lasting time course (∼200 ms) to phasic PAD measured in rodent Ia afferents. Long trains of cutaneous or proprioceptive afferent conditioning produced longer-lasting facilitation of the H-reflex for up to 2 min, consistent with tonic PAD in rodent Ia afferents mediated by nodal α5-GABAA receptors for similar stimulation trains. Facilitation of H-reflexes by this conditioning was likely not mediated by direct facilitation of the motoneurons because isolated stimulation of sensory or CST pathways did not alone facilitate the tonic firing rate of motor units. Furthermore, cutaneous conditioning increased the firing probability of single motor units (motoneurons) during the H-reflex without increasing their firing rate at this time, indicating that the underlying excitatory postsynaptic potential was more probable, but not larger. These results are consistent with sensory and CST pathways activating nodal GABAA receptors that reduce intermittent failure of action potentials propagating into Ia afferent branches. KEY POINTS: Controlled execution of posture and movement requires continually adjusted feedback from peripheral sensory pathways, especially those that carry proprioceptive information about body position, movement and effort. It was previously thought that the flow of proprioceptive feedback from Ia afferents was only reduced by GABAergic neurons in the spinal cord that sent axoaxonic projections to the terminal endings of sensory axons (termed GABAaxo neurons). Based on new findings in rodents, we provide complementary evidence in humans to suggest that sensory and corticospinal pathways known to activate GABAaxo neurons that project to dorsal parts of the Ia afferent also increase the flow of proprioceptive feedback to motoneurons in the spinal cord. These findings support a new role for spinal GABAaxo neurons in facilitating afferent feedback to the spinal cord during voluntary or reflexive movements.
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Affiliation(s)
- Krista Metz
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Isabel Concha Matos
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Yaqing Li
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Babak Afsharipour
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | | | - Francesco Negro
- Clinical and Experimental Sciences, Universita degli Studi di Brescia, Brescia, Italy
| | - Katharina A Quinlan
- George and Anne Ryan Institute for Neuroscience, Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, USA
| | - David J Bennett
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Monica A Gorassini
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
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3
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Gradwell MA, Boyle KA, Browne TJ, Bell AM, Leonardo J, Peralta Reyes FS, Dickie AC, Smith KM, Callister RJ, Dayas CV, Hughes DI, Graham BA. Diversity of inhibitory and excitatory parvalbumin interneuron circuits in the dorsal horn. Pain 2022; 163:e432-e452. [PMID: 34326298 PMCID: PMC8832545 DOI: 10.1097/j.pain.0000000000002422] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 07/13/2021] [Accepted: 07/14/2021] [Indexed: 12/03/2022]
Abstract
ABSTRACT Parvalbumin-expressing interneurons (PVINs) in the spinal dorsal horn are found primarily in laminae II inner and III. Inhibitory PVINs play an important role in segregating innocuous tactile input from pain-processing circuits through presynaptic inhibition of myelinated low-threshold mechanoreceptors and postsynaptic inhibition of distinct spinal circuits. By comparison, relatively little is known of the role of excitatory PVINs (ePVINs) in sensory processing. Here, we use neuroanatomical and optogenetic approaches to show that ePVINs comprise a larger proportion of the PVIN population than previously reported and that both ePVIN and inhibitory PVIN populations form synaptic connections among (and between) themselves. We find that these cells contribute to neuronal networks that influence activity within several functionally distinct circuits and that aberrant activity of ePVINs under pathological conditions is well placed to contribute to the development of mechanical hypersensitivity.
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Affiliation(s)
- Mark A. Gradwell
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
- Department of Cell Biology and Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
- W.M. Keck Center for Collaborative Neuroscience, Rutgers, The State University of New Jersey, Piscataway, NJ, United States
| | - Kieran A. Boyle
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Tyler J. Browne
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
| | - Andrew M. Bell
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jacklyn Leonardo
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Fernanda S. Peralta Reyes
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Allen C. Dickie
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Kelly M. Smith
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
- Department of Neurobiology and the Pittsburgh Center for Pain Research, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert J. Callister
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
| | - Christopher V. Dayas
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
| | - David I. Hughes
- Institute of Neuroscience Psychology, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Brett A. Graham
- Faculty of Health, School of Biomedical Sciences & Pharmacy, University of Newcastle, Callaghan, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, New South Wales, Australia
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4
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Presynaptic Inhibition of Pain and Touch in the Spinal Cord: From Receptors to Circuits. Int J Mol Sci 2021; 22:ijms22010414. [PMID: 33401784 PMCID: PMC7795800 DOI: 10.3390/ijms22010414] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 12/28/2020] [Accepted: 12/30/2020] [Indexed: 02/07/2023] Open
Abstract
Sensory primary afferent fibers, conveying touch, pain, itch, and proprioception, synapse onto spinal cord dorsal horn neurons. Primary afferent central terminals express a wide variety of receptors that modulate glutamate and peptide release. Regulation of the amount and timing of neurotransmitter release critically affects the integration of postsynaptic responses and the coding of sensory information. The role of GABA (γ-aminobutyric acid) receptors expressed on afferent central terminals is particularly important in sensory processing, both in physiological conditions and in sensitized states induced by chronic pain. During the last decade, techniques of opto- and chemogenetic stimulation and neuronal selective labeling have provided interesting insights on this topic. This review focused on the recent advances about the modulatory effects of presynaptic GABAergic receptors in spinal cord dorsal horn and the neural circuits involved in these mechanisms.
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Horvath PM, Piazza MK, Monteggia LM, Kavalali ET. Spontaneous and evoked neurotransmission are partially segregated at inhibitory synapses. eLife 2020; 9:52852. [PMID: 32401197 PMCID: PMC7250572 DOI: 10.7554/elife.52852] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 05/13/2020] [Indexed: 12/27/2022] Open
Abstract
Synaptic transmission is initiated via spontaneous or action-potential evoked fusion of synaptic vesicles. At excitatory synapses, glutamatergic receptors activated by spontaneous and evoked neurotransmission are segregated. Although inhibitory synapses also transmit signals spontaneously or in response to action potentials, they differ from excitatory synapses in both structure and function. Therefore, we hypothesized that inhibitory synapses may have different organizing principles. We report picrotoxin, a GABAAR antagonist, blocks neurotransmission in a use-dependent manner at rat hippocampal synapses and therefore can be used to interrogate synaptic properties. Using this tool, we uncovered partial segregation of inhibitory spontaneous and evoked neurotransmission. We found up to 40% of the evoked response is mediated through GABAARs which are only activated by evoked neurotransmission. These data indicate GABAergic spontaneous and evoked neurotransmission processes are partially non-overlapping, suggesting they may serve divergent roles in neuronal signaling.
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Affiliation(s)
- Patricia M Horvath
- Department of Pharmacology, Vanderbilt University, Nashville, United States.,Department of Neuroscience, the University of Texas Southwestern Medical Center, Dallas, United States
| | - Michelle K Piazza
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, United States.,Neuroscience Program, Vanderbilt University, Nashville, United States
| | - Lisa M Monteggia
- Department of Pharmacology, Vanderbilt University, Nashville, United States.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, United States
| | - Ege T Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, United States.,Vanderbilt Brain Institute, Vanderbilt University, Nashville, United States
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6
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Shah S, Carver CM, Mullen P, Milne S, Lukacs V, Shapiro MS, Gamper N. Local Ca 2+ signals couple activation of TRPV1 and ANO1 sensory ion channels. Sci Signal 2020; 13:13/629/eaaw7963. [PMID: 32345727 DOI: 10.1126/scisignal.aaw7963] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
ANO1 (TMEM16A) is a Ca2+-activated Cl- channel (CaCC) expressed in peripheral somatosensory neurons that are activated by painful (noxious) stimuli. These neurons also express the Ca2+-permeable channel and noxious heat sensor TRPV1, which can activate ANO1. Here, we revealed an intricate mechanism of TRPV1-ANO1 channel coupling in rat dorsal root ganglion (DRG) neurons. Simultaneous optical monitoring of CaCC activity and Ca2+ dynamics revealed that the TRPV1 ligand capsaicin activated CaCCs. However, depletion of endoplasmic reticulum (ER) Ca2+ stores reduced capsaicin-induced Ca2+ increases and CaCC activation, suggesting that ER Ca2+ release contributed to TRPV1-induced CaCC activation. ER store depletion by plasma membrane-localized TRPV1 channels was demonstrated with an ER-localized Ca2+ sensor in neurons exposed to a cell-impermeable TRPV1 ligand. Proximity ligation assays established that ANO1, TRPV1, and the IP3 receptor IP3R1 were often found in close proximity to each other. Stochastic optical reconstruction microscopy (STORM) confirmed the close association between all three channels in DRG neurons. Together, our data reveal the existence of ANO1-containing multichannel nanodomains in DRG neurons and suggest that coupling between TRPV1 and ANO1 requires ER Ca2+ release, which may be necessary to enhance ANO1 activation.
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Affiliation(s)
- Shihab Shah
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Chase M Carver
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Pierce Mullen
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Stephen Milne
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Viktor Lukacs
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark S Shapiro
- Department of Cell and Integrative Physiology, University of Texas Health San Antonio, San Antonio, TX 78229, USA
| | - Nikita Gamper
- School of Biomedical Science, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK. .,Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, People's Republic of China
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7
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Meijs S, Liao S, Arendt-Nielsen L, Wang K, Cairns BE. The pro-algesic effect of γ-aminobutyric acid (GABA) injection into the masseter muscle of healthy men and women. Scand J Pain 2019; 20:139-150. [DOI: 10.1515/sjpain-2019-0056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/11/2019] [Indexed: 11/15/2022]
Abstract
Abstract
Background and aims
Preclinical studies have reported that activation of peripheral γ-aminobutyric acid A (GABAA) receptors may result in analgesia. The current study was conducted in young healthy men (n = 30) and women (n = 28) to determine whether injections of GABA into the masseter muscle reduce pain in a sex-related manner.
Methods
The effect of injection of GABA alone, or in combination with the non-inflammatory algogen glutamate, was assessed in two separate studies. Lorazepam, a positive allosteric modulator of the GABAA-receptor, was co-injected with GABA in both studies to explore the role of this receptor in muscle pain responses of healthy human volunteers. Masticatory muscle mechanical pain intensity was recorded on an electronic visual analogue scale (VAS) while muscle pain sensitivity was assessed by determining the pressure pain threshold (PPT), tolerance and maximal jaw opening (MJO) of the subjects prior to, and again after the various intramuscular injections.
Results
Intramuscular injection of GABA alone was reported to be significantly more painful, in a concentration related manner, than saline control injections, and this pain was further increased by co-injection of lorazepam with GABA. Co-injection of GABA with glutamate was found to significantly increase glutamate-evoked masseter muscle pain in men, but not in women. There was no effect of injections of either GABA alone, or GABA with glutamate, on PPT, tolerance or maximum jaw opening.
Conclusions
Injection of GABA into the human masseter muscle appears to excite nociceptors to produce muscle pain without a longer term effect on mechanical pain sensitivity in the muscle. The findings suggest that GABA-mediated pain in humans is produced through peripheral GABAA receptor activation. The mechanism underlying the sex-related difference in the effect of GABA on glutamate-evoked muscle pain was speculated to be due to a methodological artifact.
Implications
This study was designed to detect analgesic rather than algesic effects of peripherally administered GABA, and as a result, the concentration of glutamate chosen for injection was close to the maximal pain response for healthy women, based on previously determined pain-concentration response relationships for glutamate. This may explain the finding of greater pain in men than women, when GABA and glutamate were co-injected. Overall, the findings suggest that activation of peripheral GABAA receptors in human masticatory muscle produces pain, possibly due to depolarization of the masticatory muscle afferent fibers.
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Affiliation(s)
- Suzan Meijs
- Center for Neuroplasticity and Pain, SMI, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
| | - Shaojun Liao
- Center for Somatosensory-Motor Interaction, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
| | - Lars Arendt-Nielsen
- Center for Neuroplasticity and Pain, SMI, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
- Center for Somatosensory-Motor Interaction, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
| | - Kelun Wang
- Center for Somatosensory-Motor Interaction, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
| | - Brian E. Cairns
- Center for Neuroplasticity and Pain, SMI, Department of Health Sciences and Technology, Faculty of Medicine , Aalborg University , Aalborg , Denmark
- Faculty of Pharmaceutical Sciences , University of British Columbia , Vancouver , Canada
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8
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Lucas-Osma AM, Li Y, Lin S, Black S, Singla R, Fouad K, Fenrich KK, Bennett DJ. Extrasynaptic α 5GABA A receptors on proprioceptive afferents produce a tonic depolarization that modulates sodium channel function in the rat spinal cord. J Neurophysiol 2018; 120:2953-2974. [PMID: 30256739 DOI: 10.1152/jn.00499.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of GABAA receptors on sensory axons produces a primary afferent depolarization (PAD) that modulates sensory transmission in the spinal cord. While axoaxonic synaptic contacts of GABAergic interneurons onto afferent terminals have been extensively studied, less is known about the function of extrasynaptic GABA receptors on afferents. Thus, we examined extrasynaptic α5GABAA receptors on low-threshold proprioceptive (group Ia) and cutaneous afferents. Afferents were impaled with intracellular electrodes and filled with neurobiotin in the sacrocaudal spinal cord of rats. Confocal microscopy was used to reconstruct the afferents and locate immunolabelled α5GABAA receptors. In all afferents α5GABAA receptors were found throughout the extensive central axon arbors. They were most densely located at branch points near sodium channel nodes, including in the dorsal horn. Unexpectedly, proprioceptive afferent terminals on motoneurons had a relative lack of α5GABAA receptors. When recording intracellularly from these afferents, blocking α5GABAA receptors (with L655708, gabazine, or bicuculline) hyperpolarized the afferents, as did blocking neuronal activity with tetrodotoxin, indicating a tonic GABA tone and tonic PAD. This tonic PAD was increased by repeatedly stimulating the dorsal root at low rates and remained elevated for many seconds after the stimulation. It is puzzling that tonic PAD arises from α5GABAA receptors located far from the afferent terminal where they can have relatively little effect on terminal presynaptic inhibition. However, consistent with the nodal location of α5GABAA receptors, we find tonic PAD helps produce sodium spikes that propagate antidromically out the dorsal roots, and we suggest that it may well be involved in assisting spike transmission in general. NEW & NOTEWORTHY GABAergic neurons are well known to form synaptic contacts on proprioceptive afferent terminals innervating motoneurons and to cause presynaptic inhibition. However, the particular GABA receptors involved are unknown. Here, we examined the distribution of extrasynaptic α5GABAA receptors on proprioceptive Ia afferents. Unexpectedly, these receptors were found preferentially near nodal sodium channels throughout the afferent and were largely absent from afferent terminals. These receptors produced a tonic afferent depolarization that modulated sodium spikes, consistent with their location.
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Affiliation(s)
- Ana M Lucas-Osma
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Shihao Lin
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Sophie Black
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Karim Fouad
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
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9
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Richardson PS, Peatfield AC. Protection of the Respiratory Tract – Mucus Production: A Review. J R Soc Med 2018; 73:123-6. [PMID: 7014882 PMCID: PMC1437329 DOI: 10.1177/014107688007300208] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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10
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Elghaba R, Bracci E. Dichotomous Effects of Mu Opioid Receptor Activation on Striatal Low-Threshold Spike Interneurons. Front Cell Neurosci 2017; 11:385. [PMID: 29259544 PMCID: PMC5723306 DOI: 10.3389/fncel.2017.00385] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 11/20/2017] [Indexed: 11/13/2022] Open
Abstract
Striatal low-threshold spike interneurons (LTSIs) are tonically active neurons that express GABA and nitric oxide synthase and are involved in information processing as well as neurovascular coupling. While mu opioid receptors (MORs) and their ligand encephalin are prominent in the striatum, their action on LTSIs has not been investigated. We addressed this issue carrying out whole-cell recordings in transgenic mice in which the NPY-expressing neurons are marked with green fluorescent protein (GFP). The MOR agonist (D-Ala(2), N-MePhe(4), Gly-ol)-enkephalin (DAMGO) produced dual effects on subpopulations of LTSIs. DAMGO caused inhibitory effects, accompanied by decreases of spontaneous firing, in 62% of LTSIs, while depolarizing effects (accompanied by an increase in spontaneous firing) were observed in 23% of LTSIs tested. The dual effects of DAMGO persisted in the presence of tetrodotoxin (TTX), a sodium channel blocker or in the presence of the nicotinic acetylcholine receptor antagonist mecamylamine. However, in the presence of either the GABAA receptor antagonist picrotoxin or the muscarinic cholinergic receptor antagonist atropine, DAMGO only elicited inhibitory effects on LTSIs. Furthermore, we found that DAMGO decreased the amplitude and frequency of spontaneous GABAergic events. Unexpectedly, these effects of DAMGO on spontaneous GABAergic events disappeared after blocking of the muscarinic and nicotinic cholinergic blockers, showing that GABA inputs to LTSIs are not directly modulated by presynaptic MORs. These finding suggest that activation of MORs affect LTSIs both directly and indirectly, through modulation of GABAergic and cholinergic tones. The complex balance between direct and indirect effects determines the net effect of DAMGO on LTSIs.
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Affiliation(s)
- Rasha Elghaba
- Department of Psychology, The University of Sheffield, Sheffield, United Kingdom
| | - Enrico Bracci
- Department of Psychology, The University of Sheffield, Sheffield, United Kingdom
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11
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Brown DA. Norman Bowery's discoveries about extrasynaptic and asynaptic GABA systems and their significance. Neuropharmacology 2017; 136:3-9. [PMID: 29128306 DOI: 10.1016/j.neuropharm.2017.11.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 11/04/2017] [Indexed: 11/26/2022]
Abstract
Before discovering the GABA-B receptor, Norman Bowery completed a series of studies on an extrasynaptic or asynaptic "GABA system" in the rat superior cervical sympathetic ganglion. First, he discovered an uptake system for GABA in neuroglial cells in the ganglia and in peripheral nerves, with a different substrate specificity than that in neurons. Second, he showed that accumulated GABA in sympathetic glial cells was metabolized to succinate by a transaminase enzyme. Third, he provided detailed structure-activity information about compounds activating an extrasynaptic GABA-A receptor on neurons in the rat sympathetic ganglion. Fourth, he showed that some amino acid substrates for the neuroglial transporter could indirectly stimulate neurons by releasing GABA from adjacent glial cells, and that GABA could also be released from neuroglial cells by membrane depolarization. In this review, these discoveries are briefly described and updated and some of their implications assessed. This article is part of the "Special Issue Dedicated to Norman G. Bowery".
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Affiliation(s)
- David A Brown
- Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6BT, UK.
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12
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Du X, Hao H, Yang Y, Huang S, Wang C, Gigout S, Ramli R, Li X, Jaworska E, Edwards I, Deuchars J, Yanagawa Y, Qi J, Guan B, Jaffe DB, Zhang H, Gamper N. Local GABAergic signaling within sensory ganglia controls peripheral nociceptive transmission. J Clin Invest 2017; 127:1741-1756. [PMID: 28375159 PMCID: PMC5409786 DOI: 10.1172/jci86812] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 02/02/2017] [Indexed: 01/05/2023] Open
Abstract
The integration of somatosensory information is generally assumed to be a function of the central nervous system (CNS). Here we describe fully functional GABAergic communication within rodent peripheral sensory ganglia and show that it can modulate transmission of pain-related signals from the peripheral sensory nerves to the CNS. We found that sensory neurons express major proteins necessary for GABA synthesis and release and that sensory neurons released GABA in response to depolarization. In vivo focal infusion of GABA or GABA reuptake inhibitor to sensory ganglia dramatically reduced acute peripherally induced nociception and alleviated neuropathic and inflammatory pain. In addition, focal application of GABA receptor antagonists to sensory ganglia triggered or exacerbated peripherally induced nociception. We also demonstrated that chemogenetic or optogenetic depolarization of GABAergic dorsal root ganglion neurons in vivo reduced acute and chronic peripherally induced nociception. Mechanistically, GABA depolarized the majority of sensory neuron somata, yet produced a net inhibitory effect on the nociceptive transmission due to the filtering effect at nociceptive fiber T-junctions. Our findings indicate that peripheral somatosensory ganglia represent a hitherto underappreciated site of somatosensory signal integration and offer a potential target for therapeutic intervention.
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Affiliation(s)
- Xiaona Du
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Han Hao
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Yuehui Yang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Sha Huang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Caixue Wang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Sylvain Gigout
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Rosmaliza Ramli
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
- School of Dental Sciences, Universiti Sains Malaysia, Kelantan, Malaysia
| | - Xinmeng Li
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Ewa Jaworska
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Ian Edwards
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Jim Deuchars
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine and Japan Science and Technology Agency, CREST, Maebashi, Japan
| | - Jinlong Qi
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Bingcai Guan
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - David B. Jaffe
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio, San Antonio, Texas, USA
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, China; The Key Laboratory of New Drug Pharmacology and Toxicology, Hebei Province; Shijiazhuang, China
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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13
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Tomatsu S, Kim G, Confais J, Seki K. Muscle afferent excitability testing in spinal root-intact rats: dissociating peripheral afferent and efferent volleys generated by intraspinal microstimulation. J Neurophysiol 2017; 117:796-807. [PMID: 27974451 DOI: 10.1152/jn.00874.2016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Accepted: 11/29/2016] [Indexed: 11/22/2022] Open
Abstract
Presynaptic inhibition of the sensory input from the periphery to the spinal cord can be evaluated directly by intra-axonal recording of primary afferent depolarization (PAD) or indirectly by intraspinal microstimulation (excitability testing). Excitability testing is superior for use in normal behaving animals, because this methodology bypasses the technically challenging intra-axonal recording. However, use of excitability testing on the muscle or joint afferent in intact animals presents its own technical challenges. Because these afferents, in many cases, are mixed with motor axons in the peripheral nervous system, it is crucial to dissociate antidromic volleys in the primary afferents from orthodromic volleys in the motor axon, both of which are evoked by intraspinal microstimulation. We have demonstrated in rats that application of a paired stimulation protocol with a short interstimulus interval (ISI) successfully dissociated the antidromic volley in the nerve innervating the medial gastrocnemius muscle. By using a 2-ms ISI, the amplitude of the volleys evoked by the second stimulation was decreased in dorsal root-sectioned rats, but the amplitude did not change or was slightly increased in ventral root-sectioned rats. Excitability testing in rats with intact spinal roots indicated that the putative antidromic volleys exhibited dominant primary afferent depolarization, which was reasonably induced from the more dorsal side of the spinal cord. We concluded that excitability testing with a paired-pulse protocol can be used for studying presynaptic inhibition of somatosensory afferents in animals with intact spinal roots.NEW & NOTEWORTHY Excitability testing of primary afferents has been used to evaluate presynaptic modulation of synaptic transmission in experiments conducted in vivo. However, to apply this method to muscle afferents of animals with intact spinal roots, it is crucial to dissociate antidromic and orthodromic volleys induced by spinal microstimulation. We propose a new method to make this dissociation possible without cutting spinal roots and demonstrate that it facilitates excitability testing of muscle afferents.
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Affiliation(s)
- Saeka Tomatsu
- Department of Neurophysiology, National Institute of Neuroscience, Tokyo, Japan; and
| | - Geehee Kim
- Department of Neurophysiology, National Institute of Neuroscience, Tokyo, Japan; and
| | - Joachim Confais
- Department of Neurophysiology, National Institute of Neuroscience, Tokyo, Japan; and
| | - Kazuhiko Seki
- Department of Neurophysiology, National Institute of Neuroscience, Tokyo, Japan; and .,Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama, Japan
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14
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Malomouzh AI, Petrov KA, Nurullin LF, Nikolsky EE. Metabotropic GABAB
receptors mediate GABA inhibition of acetylcholine release in the rat neuromuscular junction. J Neurochem 2015; 135:1149-60. [DOI: 10.1111/jnc.13373] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 09/16/2015] [Accepted: 09/21/2015] [Indexed: 12/25/2022]
Affiliation(s)
- Artem I. Malomouzh
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
| | - Konstantin A. Petrov
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- A.E. Arbuzov Institute of Organic and Physical Chemistry; Russian Academy of Sciences; Kazan Russia
| | - Leniz F. Nurullin
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- Kazan State Medical University; Kazan Russia
| | - Evgeny E. Nikolsky
- Kazan Institute of Biochemistry and Biophysics; Russian Academy of Sciences; Kazan Russia
- Kazan Federal University; Kazan Russia
- Kazan State Medical University; Kazan Russia
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15
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Zhang XL, Lee KY, Priest BT, Belfer I, Gold MS. Inflammatory mediator-induced modulation of GABAA currents in human sensory neurons. Neuroscience 2015; 310:401-9. [PMID: 26415765 DOI: 10.1016/j.neuroscience.2015.09.048] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 08/29/2015] [Accepted: 09/19/2015] [Indexed: 12/31/2022]
Abstract
The purpose of the present study was to characterize the properties of A-type GABA receptor (GABAA receptor) currents in human sensory neurons. Neurons were obtained from adult organ donors. GABAA currents were recorded in isolated neurons. Both large inactivating low-affinity currents and smaller persistent high-affinity currents were present in all of the 129 neurons studied from 15 donors. The kinetics of human GABAA currents were slower than those in rat sensory neurons. GABA currents were completely blocked by bicuculline (10 μM), and persistent currents were activated by the δ-subunit-preferring agonist, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridine-3-ol (THIP). The GABA current equilibrium potential was ∼ 20 mV more hyperpolarized than in rat neurons. Both low- and high-affinity currents were increased by inflammatory mediators but via different second messenger pathways. These results highlight potentially important species differences in the properties of ion channels present in their native environment and suggest the use of human sensory neurons may be a valuable tool to test compounds prior to use in humans.
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Affiliation(s)
- X-L Zhang
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - K-Y Lee
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - B T Priest
- Lilly Research Laboratories, Indianapolis, IN 46285, USA
| | - I Belfer
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - M S Gold
- Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
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16
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West S, Bannister K, Dickenson A, Bennett D. Circuitry and plasticity of the dorsal horn – Toward a better understanding of neuropathic pain. Neuroscience 2015; 300:254-75. [DOI: 10.1016/j.neuroscience.2015.05.020] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 05/07/2015] [Accepted: 05/08/2015] [Indexed: 11/24/2022]
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17
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Huang D, Huang S, Peers C, Du X, Zhang H, Gamper N. GABAB receptors inhibit low-voltage activated and high-voltage activated Ca(2+) channels in sensory neurons via distinct mechanisms. Biochem Biophys Res Commun 2015; 465:188-93. [PMID: 26239659 DOI: 10.1016/j.bbrc.2015.07.137] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 07/28/2015] [Indexed: 12/16/2022]
Abstract
Growing evidence suggests that mammalian peripheral somatosensory neurons express functional receptors for gamma-aminobutyric acid, GABAA and GABAB. Moreover, local release of GABA by pain-sensing (nociceptive) nerve fibres has also been suggested. Yet, the functional significance of GABA receptor triggering in nociceptive neurons is not fully understood. Here we used patch-clamp recordings from small-diameter cultured DRG neurons to investigate effects of GABAB receptor agonist baclofen on voltage-gated Ca(2+) currents. We found that baclofen inhibited both low-voltage activated (LVA, T-type) and high-voltage activated (HVA) Ca(2+) currents in a proportion of DRG neurons by 22% and 32% respectively; both effects were sensitive to Gi/o inhibitor pertussis toxin. Inhibitory effect of baclofen on both current types was about twice less efficacious as compared to that of the μ-opioid receptor agonist DAMGO. Surprisingly, only HVA but not LVA current modulation by baclofen was partially prevented by G protein inhibitor GDP-β-S. In contrast, only LVA but not HVA current modulation was reversed by the application of a reducing agent dithiothreitol (DTT). Inhibition of T-type Ca(2+) current by baclofen and the recovery of such inhibition by DTT were successfully reconstituted in the expression system. Our data suggest that inhibition of LVA current in DRG neurons by baclofen is partially mediated by an unconventional signaling pathway that involves a redox mechanism. These findings reinforce the idea of targeting peripheral GABA receptors for pain relief.
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Affiliation(s)
- Dongyang Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Sha Huang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Chris Peers
- Faculty of Medicine and Health, University of Leeds, Leeds, UK
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China
| | - Hailin Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China.
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, 050011, PR China; School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.
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18
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Peng F, Qu ZW, Qiu CY, Liao M, Hu WP. Spinal vasopressin alleviates formalin-induced nociception by enhancing GABAA receptor function in mice. Neurosci Lett 2015; 593:61-5. [PMID: 25782631 DOI: 10.1016/j.neulet.2015.03.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 03/06/2015] [Accepted: 03/13/2015] [Indexed: 12/18/2022]
Abstract
Arginine vasopressin (AVP) plays a regulatory role in nociception. Intrathecal administration of AVP displays an antinociceptive effect. However, little is understood about the mechanism underlying spinal AVP analgesia. Here, we have found that spinal AVP dose dependently reduced the second, but not first, phase of formalin-induced spontaneous nociception in mice. The AVP analgesia was completely blocked by intrathecal injected SR 49059, a vasopressin-1A (V1A) receptor antagonist. However, spinal AVP failed to exert its antinociceptive effect on the second phase formalin-induced spontaneous nociception in V1A receptor knock-out (V1A-/-) mice. The AVP analgesia was also reversed by bicuculline, a GABAA receptor antagonist. Moreover, AVP potentiated GABA-activated currents in dorsal root ganglion neurons from wild-type littermates, but not from V1A-/- mice. Our results may reveal a novel spinal mechanism of AVP analgesia by enhancing the GABAA receptor function in the spinal cord through V1A receptors.
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Affiliation(s)
- Fang Peng
- Institute of Ion Channels, Department of Pharmacology, Hubei University of Science and Technology, 88 Xianning Road, Xianning 437100, Hubei, PR China; Department of Anatomy and Histology & Embryology, College of Basic Medicine, Wenzou Medical University, Wenzou 32500, Zhejiang, PR China
| | - Zu-Wei Qu
- Institute of Ion Channels, Department of Pharmacology, Hubei University of Science and Technology, 88 Xianning Road, Xianning 437100, Hubei, PR China
| | - Chun-Yu Qiu
- Institute of Ion Channels, Department of Pharmacology, Hubei University of Science and Technology, 88 Xianning Road, Xianning 437100, Hubei, PR China
| | - Min Liao
- Department of Anatomy and Histology & Embryology, College of Basic Medicine, Wenzou Medical University, Wenzou 32500, Zhejiang, PR China.
| | - Wang-Ping Hu
- Institute of Ion Channels, Department of Pharmacology, Hubei University of Science and Technology, 88 Xianning Road, Xianning 437100, Hubei, PR China.
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19
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Evidence for the participation of peripheral α5 subunit-containing GABAA receptors in GABAA agonists-induced nociception in rats. Eur J Pharmacol 2014; 734:91-7. [DOI: 10.1016/j.ejphar.2014.03.051] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 03/11/2014] [Accepted: 03/22/2014] [Indexed: 11/17/2022]
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20
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Abstract
Vertebrates can sense and avoid noxious heat that evokes pain. Many thermoTRP channels are associated with temperature sensation. TRPV1 is a representative ion channel that is activated by noxious heat. Anoctamin 1 (ANO1) is a Cl- channel activated by calcium that is highly expressed in small sensory neurons, colocalized with markers for nociceptors, and most surprisingly, activated by noxious heat over 44oC. Although ANO1 is a Cl- channel, opening of this channel leads to depolarization of sensory neurons, suggesting a role in nociception. Indeed, the functional deletion of ANO1 in sensory neurons triggers the reduction in thermal pain sensation. Thus, it seems clear that ANO1 is a heat sensor in a nociceptive pathway. Since ANO1 modulators are developed for the purpose of treating chronic diseases such as cystic fibrosis, this finding is likely to predict unwanted effects and provide a guide for better developmental strategy
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Affiliation(s)
- Hawon Cho
- Sensory Research Center, CRI, College of Pharmacy, Seoul National University
| | - Uhtaek Oh
- Sensory Research Center, CRI, College of Pharmacy, Seoul National University, ; Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742, Republic of Korea
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21
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Bardoni R, Takazawa T, Tong CK, Choudhury P, Scherrer G, Macdermott AB. Pre- and postsynaptic inhibitory control in the spinal cord dorsal horn. Ann N Y Acad Sci 2013; 1279:90-6. [PMID: 23531006 DOI: 10.1111/nyas.12056] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Sensory information transmitted to the spinal cord dorsal horn is modulated by a complex network of excitatory and inhibitory interneurons. The two main inhibitory transmitters, GABA and glycine, control the flow of sensory information mainly by regulating the excitability of dorsal horn neurons. A presynaptic action of GABA has also been proposed as an important modulatory mechanism of transmitter release from sensory primary afferent terminals. By inhibiting the release of glutamate from primary afferent terminals, activation of presynaptic GABA receptors could play an important role in nociceptive and tactile sensory coding, while changes in their expression or function could be involved in pathological pain conditions, such as allodynia.
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Affiliation(s)
- Rita Bardoni
- Department of Biomedical, Metabolic and Neural Science, University of Modena and Reggio Emilia, Modena, Italy.
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22
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Paik SK, Kwak MK, Bae JY, Yi HW, Yoshida A, Ahn DK, Bae YC. γ-Aminobutyric acid-, glycine-, and glutamate-immunopositive boutons on mesencephalic trigeminal neurons that innervate jaw-closing muscle spindles in the rat: Ultrastructure and development. J Comp Neurol 2012; 520:3414-27. [DOI: 10.1002/cne.23110] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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23
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Mao S, Garzon-Muvdi T, Di Fulvio M, Chen Y, Delpire E, Alvarez FJ, Alvarez-Leefmans FJ. Molecular and functional expression of cation-chloride cotransporters in dorsal root ganglion neurons during postnatal maturation. J Neurophysiol 2012; 108:834-52. [PMID: 22457464 PMCID: PMC3424090 DOI: 10.1152/jn.00970.2011] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 03/28/2012] [Indexed: 12/30/2022] Open
Abstract
GABA depolarizes and excites central neurons during early development, becoming inhibitory and hyperpolarizing with maturation. This "developmental shift" occurs abruptly, reflecting a decrease in intracellular Cl(-) concentration ([Cl(-)](i)) and a hyperpolarizing shift in Cl(-) equilibrium potential due to upregulation of the K(+)-Cl(-) cotransporter KCC2b, a neuron-specific Cl(-) extruder. In contrast, primary afferent neurons (PANs) are depolarized by GABA throughout adulthood because of expression of NKCC1, a Na(+)-K(+)-2Cl(-) cotransporter that accumulates Cl(-) above equilibrium. The GABA(A)-mediated depolarization of PANs determines presynaptic inhibition in the spinal cord, a key mechanism gating somatosensory information. Little is known about developmental changes in Cl(-) transporter expression and Cl(-) homeostasis in PANs. Whether NKCC1 is expressed in PANs of all phenotypes or is restricted to subpopulations (e.g., nociceptors) is debatable. Likewise, whether PANs express KCC2s is controversial. We investigated NKCC1 and K(+)-Cl(-) cotransporter expression in rat and mouse dorsal root ganglion (DRG) neurons with molecular methods. Using fluorescence imaging microscopy, we measured [Cl(-)](i) in acutely dissociated rat DRG neurons (P0-P21) loaded with N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide and classified with phenotypic markers. DRG neurons of all sizes express two NKCC1 mRNAs, one full-length and a shorter splice variant lacking exon 21. Immunolabeling with validated antibodies revealed ubiquitous expression of NKCC1 in DRG neurons irrespective of postnatal age and phenotype. As maturation progresses [Cl(-)](i) decreases gradually, persisting above equilibrium in >95% mature neurons. DRG neurons express mRNAs for KCC1, KCC3s, and KCC4, but not for KCC2s. Mechanisms underlying PANs' developmental changes in Cl(-) homeostasis are discussed and compared with those of central neurons.
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Affiliation(s)
- Shihong Mao
- Department of Pharmacology and Toxicology, Boonshoft School of Medicine, Wright State University, Dayton, Ohio 45435-0001, USA
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24
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Morikawa T, Manabe T. Aberrant regulation of alternative pre-mRNA splicing in schizophrenia. Neurochem Int 2010; 57:691-704. [DOI: 10.1016/j.neuint.2010.08.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 08/07/2010] [Accepted: 08/12/2010] [Indexed: 01/06/2023]
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25
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Fischer MJM, Leffler A, Niedermirtl F, Kistner K, Eberhardt M, Reeh PW, Nau C. The general anesthetic propofol excites nociceptors by activating TRPV1 and TRPA1 rather than GABAA receptors. J Biol Chem 2010; 285:34781-92. [PMID: 20826794 PMCID: PMC2966094 DOI: 10.1074/jbc.m110.143958] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 08/19/2010] [Indexed: 11/06/2022] Open
Abstract
Anesthetic agents can induce a paradox activation and sensitization of nociceptive sensory neurons and, thus, potentially facilitate pain processing. Here we identify distinct molecular mechanisms that mediate an activation of sensory neurons by 2,6-diisopropylphenol (propofol), a commonly used intravenous anesthetic known to elicit intense pain upon injection. Clinically relevant concentrations of propofol activated the recombinant transient receptor potential (TRP) receptors TRPA1 and TRPV1 heterologously expressed in HEK293t cells. In dorsal root ganglion (DRG) neurons, propofol-induced activation correlated better to expression of TRPA1 than of TRPV1. However, pretreatment with the protein kinase C activator 4β-phorbol 12-myristate 13-acetate (PMA) resulted in a significantly sensitized propofol-induced activation of TRPV1 in DRG neurons as well as in HEK293t cells. Pharmacological and genetic silencing of both TRPA1 and TRPV1 only partially abrogated propofol-induced responses in DRG neurons. The remaining propofol-induced activation was abolished by the selective γ-aminobutyric acid, type A (GABA(A)) receptor antagonist picrotoxin. Propofol but not GABA evokes a release of calcitonin gene-related peptide, a key component of neurogenic inflammation, from isolated peripheral nerves of wild-type but not TRPV1 and TRPA1-deficient mice. Moreover, propofol but not GABA induced an intense pain upon intracutaneous injection. As both the release of calcitonin gene-related peptide and injection pain by propofol seem to be independent of GABA(A) receptors, our data identify TRPV1 and TRPA1 as key molecules for propofol-induced excitation of sensory neurons. This study warrants further investigations into the role of anesthetics to induce nociceptor sensitization and to foster postoperative pain.
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Affiliation(s)
- Michael J M Fischer
- Institute of Physiology and Pathophysiology, University of Erlangen-Nuremberg, Erlangen 91054, Germany
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26
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Xiong YC, Li XM, Wang XJ, Liu YQ, Qiu F, Wu D, Gan YB, Wang BH, Hu WP. Prokineticin 2 suppresses GABA-activated current in rat primary sensory neurons. Neuropharmacology 2010; 59:589-94. [PMID: 20800074 DOI: 10.1016/j.neuropharm.2010.08.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Revised: 08/16/2010] [Accepted: 08/16/2010] [Indexed: 10/19/2022]
Abstract
Prokineticin 2 (PK2) is a newly identified regulatory protein, which is involved in a wide range of physiological processes including pain perception in mammals. However, the precise role of PK2 in nociception is yet not fully understood. Here, we investigate the effects of PK2 on GABA(A) receptor function in rat trigeminal ganglion neurons using whole-cell patch clamp technique. PK2 reversibly depressed inward currents produced by GABA(A) receptor activation (I(GABA)) with an IC₅₀ of 0.26 ± 0.02 nM. PK2 appeared to decrease the efficacy of GABA to GABA(A) receptor but not the affinity. The maximum response of the GABA dose-response curve decreased to 71.2 ± 7.0% of control after pretreatment with PK2, while the threshold value and EC₅₀ of curve did not alter significantly. The effects of PK2 on I(GABA) were voltage independent. The PK2-induced inhibition of I(GABA) was removed by intracellular dialysis of either GDP-β-S (a non-hydrolyzable GDP analog), EGTA (a Ca²+ chelator) or GF109203X (a selective protein kinase C inhibitor), but not by H89 (a protein kinase A inhibitor). These results suggest that PK2 down-regulates the function of the GABA(A) receptor via G-protein and protein kinase C dependent signal pathways in primary sensory neurons and this depression might underlie the hyperalgesia induced by PK2.
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Affiliation(s)
- Yan-Cai Xiong
- Department of Pharmacology, Xianning College, 88 Xianning Road, Xianning 437100, Hubei, PR China
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27
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Magnaghi V. GABA and neuroactive steroid interactions in glia: new roles for old players? Curr Neuropharmacol 2010; 5:47-64. [PMID: 18615153 DOI: 10.2174/157015907780077132] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2006] [Revised: 04/24/2006] [Accepted: 07/27/2006] [Indexed: 02/06/2023] Open
Abstract
In recent years it has becoming clear that glial cells of the central and peripheral nervous system play a crucial role from the earliest stages of development throughout adult life. Glial cells are important for neuronal plasticity, axonal conduction and synaptic transmission. In this respect, glial cells are able to produce, uptake and metabolize many factors that are essential for neuronal physiology, including classic neurotransmitters and neuroactive steroids. In particular, neuroactive steroids, which are mainly synthesized by glial cells, are able to modulate some neurotransmitter receptors affecting both glia and neurons. Among the signaling systems that are specialized for neuron-glial communication, we can include neurotransmitter GABA.The main focus of this review is to illustrate the cross-talk between neurons and glial cells in terms of GABA neurotransmission and actions of neuroactive steroids. To this purpose, we will review the presence of the different GABA receptors in the glial cells of the central and peripheral nervous system. Then, we will discuss their modulation by some neuroactive steroids.
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Affiliation(s)
- Valerio Magnaghi
- Department of Endocrinology and Center of Excellence on Neurodegenerative Disease, University of Milan, Italy.
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28
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Satellite glial cells in sympathetic and parasympathetic ganglia: in search of function. ACTA ACUST UNITED AC 2010; 64:304-27. [PMID: 20441777 DOI: 10.1016/j.brainresrev.2010.04.009] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2009] [Revised: 04/14/2010] [Accepted: 04/27/2010] [Indexed: 01/08/2023]
Abstract
Glial cells are established as essential for many functions of the central nervous system, and this seems to hold also for glial cells in the peripheral nervous system. The main type of glial cells in most types of peripheral ganglia - sensory, sympathetic, and parasympathetic - is satellite glial cells (SGCs). These cells usually form envelopes around single neurons, which create a distinct functional unit consisting of a neuron and its attending SGCs. This review presents the knowledge on the morphology of SGCs in sympathetic and parasympathetic ganglia, and the (limited) available information on their physiology and pharmacology. It appears that SGCs carry receptors for ATP and can thus respond to the release of this neurotransmitter by the neurons. There is evidence that SGCs have an uptake mechanism for GABA, and possibly other neurotransmitters, which enables them to control the neuronal microenvironment. Damage to post- or preganglionic nerve fibers influences both the ganglionic neurons and the SGCs. One major consequence of postganglionic nerve section is the detachment of preganglionic nerve terminals, resulting in decline of synaptic transmission. It appears that, at least in sympathetic ganglia, SGCs participate in the detachment process, and possibly in the subsequent recovery of the synaptic connections. Unlike sensory neurons, neurons in autonomic ganglia receive synaptic inputs, and SGCs are in very close contact with synaptic boutons. This places the SGCs in a position to influence synaptic transmission and information processing in autonomic ganglia, but this topic requires much further work.
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29
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Kroeger D, Tamburri A, Amzica F, Sík A. Activity-dependent layer-specific changes in the extracellular chloride concentration and chloride driving force in the rat hippocampus. J Neurophysiol 2010; 103:1905-14. [PMID: 20130043 DOI: 10.1152/jn.00497.2009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The transmembrane distribution of chloride anions (Cl⁻) determines the direction of the Cl⁻ flux through GABA(A) receptors; this establishes whether GABA(A) receptor-mediated responses are hyperpolarizing or depolarizing in neurons. Thus an activity-dependent reduction in the efficacy of inhibitory responses can be the result of an activity-induced reduction of the Cl⁻ driving force. Using Cl(-)-sensitive electrodes, we measured the extracellular Cl⁻ concentration ([Cl⁻](o)) in each layer of the hippocampus under control conditions and after stimulation. In the control condition, [Cl⁻](o) was lower within the CA1 region (112.9 ± 1.3 mM; mean ± SD) than the CA3/dentate gyrus areas (117.7 ± 1.2 mM). Stimulation of CA3 pyramidal cells led to an increase in the [Cl⁻](o). The maximum values were observed in the stratum lacunosum-moleculare (253.4 ± 51.1 mM) and in the hilus (261 ± 43.7 mM), whereas in the granular cell layer, it reached only 159.5 ± 41 mM. The stimulation-induced [Cl⁻](o) increase was followed by a period of decreasing [Cl⁻](o) that fell below the control values. The maximum undershoot (21.6 ± 0.7 mM) was observed in the s. radiatum. Systemic application of the gap junction blocker carbenoxolone significantly decreased the stimulation-induced Cl⁻ extrusion in the dentate gyrus but only slightly modified it in the CA1 area. Carbenoxolone also drastically reduced the Cl⁻ clearance. The time constant of the Cl⁻ clearance was similar between layers (83.4 ± 15.9 ms) but increased after carbenoxolone application (207.1 ± 44.4 ms). Stimulation-induced changes in the [Cl⁻](o) significantly decreased the Cl⁻ driving force and resulted in large fluctuations between layers (Δ = 9.4 mV). The lowest value was observed in the stratum radiatum of the CA1 and the hilar region (7.7 mV), whereas the highest value was calculated for the granule cell layer (16.3 mV). We suggest that a decrease of the extracellular space is mainly responsible for the rapid [Cl⁻](o) increase while the gap junction coupled astrocytic network plays a key role in the activity-dependent redistribution and clearance of Cl⁻ across layers of the hippocampus.
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Affiliation(s)
- D Kroeger
- Centre de Recherche Université Laval Robert Giffard, University Laval, Quebec, Canada
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Carr RW, Sittl R, Fleckenstein J, Grafe P. GABA increases electrical excitability in a subset of human unmyelinated peripheral axons. PLoS One 2010; 5:e8780. [PMID: 20098693 PMCID: PMC2808338 DOI: 10.1371/journal.pone.0008780] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 12/29/2009] [Indexed: 11/28/2022] Open
Abstract
Background A proportion of small diameter primary sensory neurones innervating human skin are chemosensitive. They respond in a receptor dependent manner to chemical mediators of inflammation as well as naturally occurring algogens, thermogens and pruritogens. The neurotransmitter GABA is interesting in this respect because in animal models of neuropathic pain GABA pre-synaptically regulates nociceptive input to the spinal cord. However, the effect of GABA on human peripheral unmyelinated axons has not been established. Methodology/Principal Findings Electrical stimulation was used to assess the effect of GABA on the electrical excitability of unmyelinated axons in isolated fascicles of human sural nerve. GABA (0.1–100 µM) increased electrical excitability in a subset (ca. 40%) of C-fibres in human sural nerve fascicles suggesting that axonal GABA sensitivity is selectively restricted to a sub-population of human unmyelinated axons. The effects of GABA were mediated by GABAA receptors, being mimicked by bath application of the GABAA agonist muscimol (0.1–30 µM) while the GABAB agonist baclofen (10–30 µM) was without effect. Increases in excitability produced by GABA (10–30 µM) were blocked by the GABAA antagonists gabazine (10–20 µM), bicuculline (10–20 µM) and picrotoxin (10–20 µM). Conclusions/Significance Functional GABAA receptors are present on a subset of unmyelinated primary afferents in humans and their activation depolarizes these axons, an effect likely due to an elevated intra-axonal chloride concentration. GABAA receptor modulation may therefore regulate segmental and peripheral components of nociception.
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Affiliation(s)
- Richard W Carr
- Institute of Physiology, Ludwig-Maximilians University, Munich, Germany.
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Seki K, Perlmutter SI, Fetz EE. Task-dependent modulation of primary afferent depolarization in cervical spinal cord of monkeys performing an instructed delay task. J Neurophysiol 2009; 102:85-99. [PMID: 19386753 PMCID: PMC2712276 DOI: 10.1152/jn.91113.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Accepted: 04/14/2009] [Indexed: 11/22/2022] Open
Abstract
Task-dependent modulation of primary afferent depolarization (PAD) was studied in the cervical spinal cord of two monkeys performing a wrist flexion and extension task with an instructed delay period. We implanted two nerve cuff electrodes on proximal and distal parts of the superficial radial nerve (SR) and a recording chamber over a hemi-laminectomy in the lower cervical vertebrae. Antidromic volleys (ADVs) in the SR were evoked by intraspinal microstimuli (ISMS, 3-10 Hz, 3-30 microA) applied through a tungsten microelectrode, and the area of each ADV was measured. In total, 434 ADVs were evoked by ISMS in two monkeys, with onset latency consistently shorter in the proximal than distal cuffs. Estimated conduction velocity suggest that most ADVs were caused by action potentials in cutaneous fibers originating from low-threshold tactile receptors. Modulation of the size of ADVs as a function of the task was examined in 281 ADVs induced by ISMS applied at 78 different intraspinal sites. The ADVs were significantly facilitated during active movement in both flexion and extension (P<0.05), suggesting an epoch-dependent modulation of PAD. This facilitation started 400-900 ms before the onset of EMG activity. Such pre-EMG modulation is hard to explain by movement-induced reafference and probably is associated with descending motor commands.
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Affiliation(s)
- Kazuhiko Seki
- Department of Developmental Physiology, National Institute for Physiological Sciences, 38 Nishi-gounaka, Myodaiji, Okazaki, Aichi 444-8585, Japan.
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Price TJ, Cervero F, Gold MS, Hammond DL, Prescott SA. Chloride regulation in the pain pathway. BRAIN RESEARCH REVIEWS 2009; 60:149-70. [PMID: 19167425 PMCID: PMC2903433 DOI: 10.1016/j.brainresrev.2008.12.015] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/29/2008] [Indexed: 12/18/2022]
Abstract
Melzack and Wall's Gate Control Theory of Pain laid the theoretical groundwork for a role of spinal inhibition in endogenous pain control. While the Gate Control Theory was based on the notion that spinal inhibition is dynamically regulated, mechanisms underlying the regulation of inhibition have turned out to be far more complex than Melzack and Wall could have ever imagined. Recent evidence indicates that an exquisitely sensitive form of regulation involves changes in anion equilibrium potential (E(anion)), which subsequently impacts fast synaptic inhibition mediated by GABA(A), and to a lesser extent, glycine receptor activation, the prototypic ligand gated anion channels. The cation-chloride co-transporters (in particular NKCC1 and KCC2) have emerged as proteins that play a critical role in the dynamic regulation of E(anion) which in turn appears to play a critical role in hyperalgesia and allodynia following peripheral inflammation or nerve injury. This review summarizes the current state of knowledge in this area with particular attention to how such findings relate to endogenous mechanisms of hyperalgesia and allodynia and potential applications for therapeutics based on modulation of intracellular Cl(-) gradients or pharmacological interventions targeting GABA(A) receptors.
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Affiliation(s)
| | - Fernando Cervero
- McGill University, Department of Anesthesia, McGill Centre for Research on Pain,
| | | | - Donna L Hammond
- University of Iowa, Department of Anesthesia, Department of Pharmacology,
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Abstract
The fundamental role of calcium ions (Ca(2+)) in an excitable tissue, the frog heart, was first demonstrated in a series of classical reports by Sydney Ringer in the latter part of the nineteenth century (1882a, b; 1893a, b). Even so, nearly a century elapsed before it was proven that Ca(2+) regulated the excitability of primary sensory neurons. In this chapter we review the sites and mechanisms whereby internal and external Ca(2+) can directly or indirectly alter the excitability of primary sensory neurons: excitability changes being manifested typically by variations in shape of the action potential or the pattern of its discharge.
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Modulation of chloride homeostasis by inflammatory mediators in dorsal root ganglion neurons. Mol Pain 2008; 4:32. [PMID: 18700020 PMCID: PMC2526990 DOI: 10.1186/1744-8069-4-32] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Accepted: 08/12/2008] [Indexed: 01/10/2023] Open
Abstract
Background Chloride currents in peripheral nociceptive neurons have been implicated in the generation of afferent nociceptive signals, as Cl- accumulation in sensory endings establishes the driving force for depolarizing, and even excitatory, Cl- currents. The intracellular Cl- concentration can, however, vary considerably between individual DRG neurons. This raises the question, whether the contribution of Cl- currents to signal generation differs between individual afferent neurons, and whether the specific Cl- levels in these neurons are subject to modulation. Based on the hypothesis that modulation of the peripheral Cl- homeostasis is involved in the generation of inflammatory hyperalgesia, we examined the effects of inflammatory mediators on intracellular Cl- concentrations and on the expression levels of Cl- transporters in rat DRG neurons. Results We developed an in vitro assay for testing how inflammatory mediators influence Cl- concentration and the expression of Cl- transporters. Intact DRGs were treated with 100 ng/ml NGF, 1.8 μM ATP, 0.9 μM bradykinin, and 1.4 μM PGE2 for 1–3 hours. Two-photon fluorescence lifetime imaging with the Cl--sensitive dye MQAE revealed an increase of the intracellular Cl- concentration within 2 hours of treatment. This effect coincided with enhanced phosphorylation of the Na+-K+-2Cl- cotransporter NKCC1, suggesting that an increased activity of that transporter caused the early rise of intracellular Cl- levels. Immunohistochemistry of NKCC1 and KCC2, the main neuronal Cl- importer and exporter, respectively, exposed an inverse regulation by the inflammatory mediators. While the NKCC1 immunosignal increased, that of KCC2 declined after 3 hours of treatment. In contrast, the mRNA levels of the two transporters did not change markedly during this time. These data demonstrate a fundamental transition in Cl- homeostasis toward a state of augmented Cl- accumulation, which is induced by a 1–3 hour treatment with inflammatory mediators. Conclusion Our findings indicate that inflammatory mediators impact on Cl- homeostasis in DRG neurons. Inflammatory mediators raise intracellular Cl- levels and, hence, the driving force for depolarizing Cl- efflux. These findings corroborate current concepts for the role of Cl- regulation in the generation of inflammatory hyperalgesia and allodynia. As the intracellular Cl- concentration rises in DRG neurons, afferent signals can be boosted by excitatory Cl- currents in the presynaptic terminals. Moreover, excitatory Cl- currents in peripheral sensory endings may also contribute to the generation or modulation of afferent signals, especially in inflamed tissue.
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Rocha-González HI, Mao S, Alvarez-Leefmans FJ. Na+,K+,2Cl- cotransport and intracellular chloride regulation in rat primary sensory neurons: thermodynamic and kinetic aspects. J Neurophysiol 2008; 100:169-84. [PMID: 18385481 DOI: 10.1152/jn.01007.2007] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adult primary afferent neurons are depolarized by GABA throughout their entire surface, including their somata located in dorsal root ganglia (DRG). Primary afferent depolarization (PAD) mediated by GABA released from spinal interneurons determines presynaptic inhibition, a key mechanism in somatosensory processing. The depolarization is due to Cl(-) efflux through GABA(A) channels; the outward Cl(-) gradient is generated by a Na+,K+,2Cl(-) cotransporter (NKCC) as first established in amphibians. Using fluorescence imaging microscopy we measured [Cl(-)]i and cell water volume (CWV) in dissociated rat DRG cells (P0-P21) loaded with N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide and calcein, respectively. Basal [Cl(-)]i was 44.2 +/- 1.2 mM (mean +/- SE), Cl(-) equilibrium potential (E Cl) was -27.0 +/- 0.7 mV (n = 75). This [Cl(-)]i is about four times higher than electrochemical equilibrium. On isosmotic removal of external Cl(-), cells lost Cl(-) and shrank. On returning to control solution, cells reaccumulated Cl(-) and recovered CWV. Cl(-) reaccumulation had Na+-dependent (SDC) and Na+-independent (SIC) components. The SIC stabilized at [Cl(-)]i = 13.2 +/- 1.2 mM, suggesting that it was passive (E(Cl) = -60.5 +/- 3 mV). Bumetanide blocked CWV recovery and most (65%) of the SDC (IC50 = 5.7 microM), indicating that both were mediated by NKCC. Active Cl(-) uptake fell with increasing [Cl(-)]i and became negligible when [Cl(-)]i reached basal levels. The kinetics of active Cl(-) uptake suggests a negative feedback system in which intracellular Cl(-)regulates its own influx thereby keeping [Cl(-)]i constant, above electrochemical equilibrium but below the value that would attain if NKCC reached thermodynamic equilibrium.
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Affiliation(s)
- Héctor I Rocha-González
- Department of Pharmacology and Toxicology, Wright State University, Boonshoft School of Medicine, Dayton, Ohio 45435-0001, USA
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Gilbert D, Franjic-Würtz C, Funk K, Gensch T, Frings S, Möhrlen F. Differential maturation of chloride homeostasis in primary afferent neurons of the somatosensory system. Int J Dev Neurosci 2007; 25:479-89. [PMID: 17869474 DOI: 10.1016/j.ijdevneu.2007.08.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2007] [Revised: 07/23/2007] [Accepted: 08/06/2007] [Indexed: 11/28/2022] Open
Abstract
Recent research into the generation of hyperalgesia has revealed that both the excitability of peripheral nociceptors and the transmission of their afferent signals in the spinal cord are subject to modulation by Cl(-) currents. The underlying Cl(-) homeostasis of nociceptive neurons, in particular its postnatal maturation, is, however, poorly understood. Here we measure the intracellular Cl(-) concentration, [Cl(-)]i, of somatosensory neurons in intact dorsal root ganglia of mice. Using two-photon fluorescence-lifetime imaging microscopy, we determined [Cl(-)]i in newborn and adult animals. We found that the somatosensory neurons undergo a transition of Cl(-) homeostasis during the first three postnatal weeks that leads to a decline of [Cl(-)]i in most neurons. Immunohistochemistry showed that a major fraction of neurons in the dorsal root ganglia express the cation-chloride co-transporters NKCC1 and KCC2, indicating that the molecular equipment for Cl(-) accumulation and extrusion is present. RT-PCR analysis showed that the transcription pattern of electroneutral Cl(-) co-transporters does not change during the maturation process. These findings demonstrate that dorsal root ganglion neurons undergo a developmental transition of chloride homeostasis during the first three postnatal weeks. This process parallels the developmental "chloride switch" in the central nervous system. However, while most CNS neurons achieve homogeneously low [Cl(-)]i levels - which is the basis of GABAergic and glycinergic inhibition - somatosensory neurons maintain a heterogeneous pattern of [Cl(-)]i values. This suggests that Cl(-) currents are excitatory in some somatosensory neurons, but inhibitory in others. Our results are consistent with the hypothesis that Cl(-) homeostasis in somatosensory neurons is regulated through posttranslational modification of cation-chloride co-transporters.
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Affiliation(s)
- Daniel Gilbert
- Department of Molecular Physiology, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
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Magnaghi V, Ballabio M, Consoli A, Lambert JJ, Roglio I, Melcangi RC. GABA receptor-mediated effects in the peripheral nervous system: A cross-interaction with neuroactive steroids. J Mol Neurosci 2006; 28:89-102. [PMID: 16632878 DOI: 10.1385/jmn:28:1:89] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2005] [Revised: 11/30/1999] [Accepted: 08/18/2005] [Indexed: 12/18/2022]
Abstract
Gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the adult mammalian central nervous system (CNS), exerts its action via an interaction with specific receptors (e.g., GABAA and GABAB). These receptors are expressed not only in neurons but also on glial cells of the CNS, which might represent a target for the allosteric action of neuroactive steroids. Herein, we have demonstrated first that in the peripheral nervous system (PNS), the sciatic nerve and myelin-producing Schwann cells express both GABAA and GABAB receptors. Specific ligands, muscimol and baclofen, respectively, control Schwann-cell proliferation and expression of some specific myelin proteins (i.e., glycoprotein P0 and peripheral myelin protein 22 [PMP22]). Moreover, the progesterone (P) metabolite allopregnanolone, acting via the GABAA receptor, can influence PMP22 synthesis. In addition, we demonstrate that P, dihydroprogesterone, and allopregnanolone influence the expression of GABAB subunits in Schwann cells. The results suggest, at least in the myelinating cells of the PNS, a cross-interaction within the GABAergic receptor system, via GABAA and GABAB receptors and neuroactive steroids.
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Affiliation(s)
- Valerio Magnaghi
- Department of Endocrinology and Center of Excellence on Neurodegenerative Diseases, University of Milan, 20133 Milan, Italy.
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Abstract
Presynaptic inhibition is one of many areas of neurophysiology in which Sir John Eccles did pioneering work. Frank and Fuortes first described presynaptic inhibition in 1957. Subsequently, Eccles and his colleagues characterized the process more fully and showed its relationship to primary afferent depolarization. Eccles' studies emphasized presynaptic inhibition of the group Ia monosynaptic reflex pathway but also included group Ib, II and cutaneous afferent pathways, and the dorsal column nuclei. Presynaptic inhibition of the group Ia afferent pathway was demonstrated by depression of monosynaptic excitatory postsynaptic potentials and inhibition of monosynaptic reflex discharges. Primary afferent depolarization was investigated by recordings of dorsal root potentials, dorsal root reflexes, cord dorsum and spinal cord field potentials, and tests of the excitability of primary afferent terminals. Primary afferent depolarization was proposed to result in presynaptic inhibition by reducing the amplitude of the action potential as it invades presynaptic terminals. This resulted in less calcium influx and, therefore, less transmitter release. Presynaptic inhibition and primary afferent depolarization could be blocked by antagonists of GABA(A) receptors, implying a role of interneurons that release gamma aminobutyric acid in the inhibitory circuit. The reason why afferent terminals were depolarized was later explained by a high intracellular concentration of Cl(-) ions in primary sensory neurons. Activation of GABA(A) receptors opens Cl(-) channels, and Cl(-) efflux results in depolarization. Another proposed mechanism of depolarization was an increase in extracellular concentration of K(+) following neural activity. Eccles' work on presynaptic inhibition has since been extended in a variety of ways.
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Affiliation(s)
- William D Willis
- Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, 77555-1069, USA.
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Hilaire C, Campo B, André S, Valmier J, Scamps F. K(+) current regulates calcium-activated chloride current-induced after depolarization in axotomized sensory neurons. Eur J Neurosci 2006; 22:1073-80. [PMID: 16176348 DOI: 10.1111/j.1460-9568.2005.04271.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
One of the major electrophysiological effects of axotomy is a hyperexcitability of injured afferents that is thought to be involved in peripheral neuropathic pain. The molecular determinants of injured sensory neuron excitability are complex and not all have been identified. We have previously shown that sciatic nerve section upregulates the Ca(2+)-activated Cl(-) current in subsets of medium and large sensory neurons. In the peripheral nervous system, the Ca(2+)-activated Cl(-) current can promote after depolarization (ADP) and may therefore be involved in excitability. In this study, we set the conditions for Ca(2+)-activated Cl(-) current activation during the electrical activity of axotomized sensory neurons. We used the whole-cell patch-clamp technique and Ca(2+) fluorescence measurements to record electrical activity or ionic currents associated with intracellular Ca(2+) transients. An analysis of Ca(2+) fluorescence variation under Ca(2+)-activated Cl(-) current activation showed that the Ca(2+) sensitivity of the Ca(2+)-activated Cl(-) current did not allow activation upon one action potential (AP) but instead necessitated intracellular Ca(2+) loading under high-frequency electrical activity or AP lengthening. Nevertheless, ADP was exclusively recorded under AP lengthening following K(+) current inhibition with either extracellular tetraethylammonium or intracellular Cs(+). The measurement of APs and ionic currents associated with the use of niflumic acid to inhibit Cl(-) currents showed that the Ca(2+)-activated Cl(-) current was responsible for the ADP observed during K(+) current inhibition. Thus, the Ca(2+)-activated Cl(-) current-induced ADP in axotomized sensory neurons is regulated by K(+) current density.
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Affiliation(s)
- Cécile Hilaire
- INSERM U 583, Hôpital St Eloi, 34295 Montpellier, France
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Price TJ, Cervero F, de Koninck Y. Role of cation-chloride-cotransporters (CCC) in pain and hyperalgesia. Curr Top Med Chem 2005; 5:547-55. [PMID: 16022677 PMCID: PMC1472095 DOI: 10.2174/1568026054367629] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The importance of the GABAergic system in spinal nociceptive processing has long been appreciated but we have only recently begun to understand how this system is modulated by the regulation of anion gradients. In neuronal tissues, cation-chloride cotransporters regulate Cl- homeostasis and the activity and/or expression of these transporters has important implications for the direction and magnitude of anion flow through GABA-A channels. Here we review recent evidence that two cation-chloride cotransporters, NKCC1 and KCC2 are involved in pain and enhanced nociception. On the one hand, NKCC1 activity is upregulated in primary afferents following an inflammatory insult and this produces excessive GABAergic depolarization in primary afferents leading to cross excitation between low and high threshold afferents. On the other hand, KCC2 expression is reduced in dorsal horn neurons following peripheral nerve injury resulting in a loss of GABA-/glycinergic inhibitory tone and, in some cases, inverting its action into net excitation. Pharmacological targeting of these cation chloride cotransporters to restore normal GABA-/glycinergic transmission in the spinal cord represents an entirely novel approach to the development of analgesics.
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Affiliation(s)
- Theodore J Price
- Anesthesia Research Unit (Faculty of Medicine), Faculty of Dentistry and McGill Center for Pain Research. McGill University, Montréal, Québec, Canada
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Norekian TP, Malyshev AY. Coordinated Excitatory Effect of GABAergic Interneurons on Three Feeding Motor Programs in the MolluskClione limacina. J Neurophysiol 2005; 93:305-15. [PMID: 15331621 DOI: 10.1152/jn.00722.2004] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Coordination between different motor centers is essential for the orderly production of all complex behaviors. Understanding the mechanisms of such coordination during feeding behavior in the carnivorous mollusk Clione limacina is the main goal of the current study. A bilaterally symmetrical interneuron identified in the cerebral ganglia and designated Cr-BM neuron produced coordinated activation of neural networks controlling three main feeding structures: prey capture appendages called buccal cones, chitinous hooks used for prey extraction from the shell, and the toothed radula. The Cr-BM neuron produced strong excitatory inputs to motoneurons controlling buccal cone protraction. It also induced a prominent activation of the neural networks controlling radula and hook rhythmic movements. In addition to the overall activation, Cr-BM neuron synaptic inputs to individual motoneurons coordinated their activity in a phase-dependent manner. The Cr-BM neuron produced depolarizing inputs to the radula protractor and hook retractor motoneurons, which are active in one phase, and hyperpolarizing inputs to the radula retractor and hook protractor motoneurons, which are active in the opposite phase. The Cr-BM neuron used GABA as its neurotransmitter. It was found to be GABA-immunoreactive in the double-labeling experiments. Exogenous GABA mimicked the effects produced by Cr-BM neuron on the postsynaptic neurons. The GABA antagonists bicuculline and picrotoxin blocked Cr-BM neuron-induced PSPs. The prominent coordinating effect produced by the Cr-BM neuron on the neural networks controlling three major elements of the feeding behavior in Clione suggests that this interneuron is an important part of the higher-order system for the feeding behavior.
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Affiliation(s)
- Tigran P Norekian
- Arizona State University, School of Life Sciences, Tempe, AZ 85287-4501, USA.
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Verdier D, Lund JP, Kolta A. Synaptic Inputs to Trigeminal Primary Afferent Neurons Cause Firing and Modulate Intrinsic Oscillatory Activity. J Neurophysiol 2004; 92:2444-55. [PMID: 15381749 DOI: 10.1152/jn.00279.2004] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this paper, we investigated the influence of synapses on the cell bodies of trigeminal muscle spindle afferents that lie in the trigeminal mesencephalic nucleus (NVmes), using intracellular recordings in brain stem slices of young rats. Three types of synaptic responses could be evoked by electrical stimulation of the adjacent supratrigeminal, motor, and main sensory nuclei and the intertrigeminal area: monophasic depolarizing postsynaptic potentials (PSPs), biphasic PSPs, and all or none action potentials without underlying excitatory PSPs (EPSPs). Many PSPs and spikes were abolished by bath-application of 6,7-dinitroquinoxaline (DNQX) alone or combined with d,l-2-amino-5-phosphonovaleric acid (APV), suggesting that they are mediated by non– N-methyl-d-aspartate (NMDA) and NMDA glutamatergic receptors, while some action potentials were sensitive to bicuculline, indicating involvement of GABAA receptors. A number of cells showed spontaneous membrane potential oscillations, and stimulation of synaptic inputs increased the amplitude of the oscillations for several cycles, which often triggered repetitive firing. Furthermore, the oscillatory rhythm was reset by the stimulation. Our results show that synaptic inputs to muscle primary afferent neurons in NVmes from neighboring areas are mainly excitatory and that they cause firing. In addition, the inputs synchronize intrinsic oscillations, which may lead to sustained, synchronous firing in a subpopulation of afferents. This may be of importance during rapid biting and during the mastication of very hard or tough foods.
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Affiliation(s)
- Dorly Verdier
- Centre de Recherche en Sciences Neurologiques, Université de Montréal, Montreal, Quebec H3C 3J7, Canada
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Affiliation(s)
- Michael A Rogawski
- Epilepsy Research Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Fabbro A, Nistri A. Chronic NGF treatment of rat nociceptive DRG neurons in culture facilitates desensitization and deactivation of GABAA receptor-mediated currents. Br J Pharmacol 2004; 142:425-34. [PMID: 15148248 PMCID: PMC1574974 DOI: 10.1038/sj.bjp.0705813] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 03/25/2004] [Accepted: 03/26/2004] [Indexed: 11/08/2022] Open
Abstract
1 The present study tested the hypothesis that nerve growth factor (NGF) could affect presynaptic inhibition mediated by GABAA (GABA-sensitive ionotropic receptors) receptors on the afferents of nociceptive dorsal root ganglia (DRG) neurons, thus reducing the filtering of central nociceptive signals. 2 To investigate this issue, small-diameter, nociceptive DRG neurons were cultured for 48-72 h either in the normal medium or in the presence of NGF (50 ng ml(-1)). After 15 min washout, cells were patch clamped with Cs+ containing electrodes to block GABAB (GABA-sensitive metabotropic receptors) receptor-activated currents. 3 Chronically treated DRG neurons showed no difference in the peak amplitude of GABA-induced currents. However, NGF-treated cells exhibited increased fading of the response to continuous GABA application, with faster desensitization onset, decreased residual current at the end of agonist application and slower recovery from desensitization. Moreover, the deactivation phase after brief agonist pulses was also accelerated. 4 Unlike responses to GABA, chronic NGF treatment had no effect on the desensitization process to the excitatory transmitter ATP, as no difference in peak amplitude, fast and slow time constants of current decay was found. 5 Experimental tests indicated that the observed effects on GABA currents were not a reactive process triggered by washing out NGF after its long application. Acutely applied NGF did not change GABAA receptor-mediated responses. 6 NGF-treated neurons showed decreased sensitivity to the antagonist picrotoxin. The action of pentobarbitone, midazolam, bicuculline or gabazine was, however, unchanged. 7 These observations suggest that the modulation of GABAA receptor function of DRG nociceptors by NGF may contribute to the algogenic action of this neurotrophin.
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Affiliation(s)
- Alessandra Fabbro
- Neurobiology Sector and INFM Unit, International School for Advanced Studies, SISSA, via Beirut, 34014 Trieste , Italy
| | - Andrea Nistri
- Neurobiology Sector and INFM Unit, International School for Advanced Studies, SISSA, via Beirut, 34014 Trieste , Italy
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Kang SH, Vanden Berghe P, Smith TK. Ca2+-activated Cl- current in cultured myenteric neurons from murine proximal colon. Am J Physiol Cell Physiol 2003; 284:C839-47. [PMID: 12456397 DOI: 10.1152/ajpcell.00437.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Whole cell patch-clamp recordings were made from cultured myenteric neurons taken from murine proximal colon. The micropipette contained Cs(+) to remove K(+) currents. Depolarization elicited a slowly activating time-dependent outward current (I(tdo)), whereas repolarization was followed by a slowly deactivating tail current (I(tail)). I(tdo) and I(tail) were present in approximately 70% of neurons. We identified these currents as Cl(-) currents (I(Cl)), because changing the transmembrane Cl(-) gradient altered the measured reversal potential (E(rev)) of both I(tdo) and I(tail) with that for I(tail) shifted close to the calculated Cl(-) equilibrium potential (E(Cl)). I(Cl) are Ca(2+)-activated Cl(-) current [I(Cl(Ca))] because they were Ca(2+) dependent. E(Cl), which was measured from the E(rev) of I(Cl(Ca)) using a gramicidin perforated patch, was -33 mV. This value is more positive than the resting membrane potential (-56.3 +/- 2.7 mV), suggesting myenteric neurons accumulate intracellular Cl(-). omega-Conotoxin GIVA [0.3 microM; N-type Ca(2+) channel blocker] and niflumic acid [10 microM; known I(Cl(Ca)) blocker], decreased the I(Cl(Ca)). In conclusion, these neurons have I(Cl(Ca)) that are activated by Ca(2+) entry through N-type Ca(2+) channels. These currents likely regulate postspike frequency adaptation.
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Affiliation(s)
- Sok Han Kang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
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Pannese E. Perikaryal surface specializations of neurons in sensory ganglia. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 220:1-34. [PMID: 12224547 DOI: 10.1016/s0074-7696(02)20002-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Slender projections, similar to microvilli, are the main specialization of the perikaryal surface of sensory ganglion neurons. The extent of these projections correlates closely with the volume of the corresponding nerve cell body. It is likely that the role of perikaryal projections of sensory ganglion neurons, which lack dendrites, is to maintain the surface-to-volume ratio of the nerve cell body above some critical level for adequate metabolic exchange. Satellite cells probably have the ability to promote, or provide a permissive environment for, the outgrowth of these projections. It is not yet known whether the effect of satellite cells is mediated by molecules associated with their plasma membrane or by diffusible factors. Furthermore, receptor molecules for numerous chemical agonists are located on the nerve cell body surface, but it is not known whether certain molecules are located exclusively on perikaryal projections or are also present on the smooth surface between these projections. Further study of the nerve cell body surface and of the influence that satellite cells exert on it will improve our understanding of the interactions between sensory ganglion neurons and satellite neuroglial cells.
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Affiliation(s)
- Ennio Pannese
- Institute of Histology, Embryology, and Neurocytology, University of Milan, Italy
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Abstract
In the CNS, gamma-aminobutyric acid (GABA) acts as an inhibitory transmitter via ligand-gated GABA(A) receptor channels and G protein-coupled GABA(B) receptors. Both of these receptor types mediate inhibitory postsynaptic transmission throughout the nervous system. For GABA(A) receptors, this inhibitory action is associated with a hyperpolarization due to an increase in conductance to chloride ions. Previous studies show that GABA(A) receptor activation in neonatal neurons and spinal cord neurons can be excitatory. Two papers recently appeared that clearly demonstrate that GABA can have a depolarizing and excitatory action in mature cortical neurons. Here we discuss the evolving story on chloride ion homeostasis in CNS neurons and its role in the bipolar life of the GABA(A) receptor.
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Affiliation(s)
- Valentin Stein
- Departments of Cellular and Molecular Pharmacology and Physiology, University of California, San Francisco, San Francisco, CA 94143, USA
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Abstract
We studied the molecular basis of GABA(A) receptor (GABA(A)R) expressed in the rat mesencephalic trigeminal (Vmes) sensory neuron using the immunohistochemical and single-cell RT-PCR methods. Using anti-GABA(A)R alpha2 subunit antibody, abundant GABA(A)Rs were visualized in Vmes neurons. A single-cell RT-PCR clarified that GABA(A)Rs expressed in Vmes neurons were predominantly composed of alpha2, alpha5, beta1, gamma1 and gamma2 subunits. Novel splicing variants in both alpha5 and beta1 were found invariably, and they lacked multiple amino acid sequence in the extracellular N-terminal portion. Known functional roles of both beta and gamma subunits in regulating the expression at the cell surface suggest that the unique subunit composition of GABA(A)Rs may be involved in the characteristics of GABA(A) response in Vmes neurons.
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Affiliation(s)
- Hisayoshi Ishii
- Division of Brain Research, Research institute of Health Sciences, Health Sciences University of Hokkaido, Youngnam Kang Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
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Kaczyńska K, Szereda-Przestaszewska M. Apnoeic response to stimulation of peripheral GABA receptors in rats. Respir Physiol Neurobiol 2002; 131:189-97. [PMID: 12126920 DOI: 10.1016/s1569-9048(02)00021-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Respiratory effects of intracarotid injection of gamma-amino-butyric acid (GABA) were investigated in two groups of rats. In the first group of 12 rats the effects of GABA were checked in the intact state, following bilateral vagotomy and GABA receptor blockade. The second group consisted of five initially vagotomized rats, challenged with GABA prior to and after bilateral carotid chemodenervation (CSN-cut). All rats were urethane and chloralose anaesthetized and spontaneously breathing. Injection of 39 micromol/kg GABA prior to and after vagotomy induced an expiratory apnoea of, respectively 5.5+/-0.84 sec and 3.9+/-0.6 sec duration (mean+/-S.E.M.), P>0.05 in all 12 rats. In breaths that followed the apnoea tidal volume increased above the control level by 23.3% (P<0.01) and 25.6% (P<0.01) pre- and post-vagotomy, respectively. Blockade of GABA receptors with bicuculline and picrotoxin abolished the inhibition of breathing. In five vagotomized rats with intact carotid sinus nerves (CSNs) intracarotid GABA challenge increased tidal volume by 39% compared with baseline breathing (P<0.05). Section of the CSNs precluded the occurrence of apnoea and undergoing respiratory changes evoked by GABA. Intracarotid GABA caused significant decrease in the mean blood pressure independent of the neural state, but the fall was delayed by CSNs neurotomy. Results of this study indicate that GABA given systemically induces apnoea followed by post-apnoeic hyperventilation. Carotid bodies are required for the ventilatory response to GABA; vagal afferents are not involved in this response.
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Affiliation(s)
- Katarzyna Kaczyńska
- Laboratory of Respiration Physiology, Department of Neurophysiology, Polish Academy of Sciences Medical Research Centre, 5 Pawińskiego Street, 02-106, Warsaw, Poland.
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El Manira A, Clarac F. GABA-Mediated Presynaptic Inhibition in Crayfish Primary Afferents by Non-A, Non-B GABA Receptors. Eur J Neurosci 2002; 3:1208-1218. [PMID: 12106220 DOI: 10.1111/j.1460-9568.1991.tb00055.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
GABAergic presynaptic inhibition has been investigated in primary afferents using an in vitro preparation of the crayfish, Procambarus clarkii. Presynaptic terminals of a leg proprioceptor, the coxo-basal (CB) chordotonal organ, were impaled in the neuorpil of the 5th thoracic ganglion. Pressure ejection of small volumes of the GABAA or GABAB receptor agonists, muscimol and 3-aminopropylphosphinic acid (3-APA), both induce depolarizing responses in the impaled CB sensory terminal. These depolarizations are not blocked by the specific GABAA and GABAB receptor antagonists, SR-95531 and phaclofen, but they are abolished by picrotoxin. Both muscimol- and 3-APA-induced depolarizations are carried by an increase in conductance to Cl-. The presynaptic increase in conductance to Cl- by GABA receptor activation leads to a depression of sensory synaptic transmission through a shunting of the incoming spikes. Monosynaptic EPSPs elicited in motor neurons by CB sensory nerve stimulation are depressed by muscimol and 3-APA. GABA-mediated presynaptic modulation occurs in crayfish primary afferents which can adjust the gain of reflexes. These results show that GABA-activated Cl- channels can induce a modulation of synaptic transmission, but also that the distinction between GABAA and GABAB receptors, as in vertebrates, is not applicable to the crustacean primary afferents.
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Affiliation(s)
- A. El Manira
- Laboratoire de Neurosciences Fonctionnelles, LNF2, CNRS, 31, Chemin J. Aiguier, 13402 Marseille Cedex 9, France
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