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Aziz HC, Mangieri RA. Sex differences in membrane properties and cellular excitability of dopamine D1 receptor-expressing neurons within the shell of the nucleus accumbens of pre- and mid-adolescent mice. Biol Sex Differ 2024; 15:54. [PMID: 39003495 PMCID: PMC11245857 DOI: 10.1186/s13293-024-00631-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 07/02/2024] [Indexed: 07/15/2024] Open
Abstract
BACKGROUND The transition from childhood to adulthood, or adolescence, a developmental stage, is characterized by psychosocial and biological changes. The nucleus accumbens (NAc), a striatal brain region composed of the core (NAcC) and shell (NAcSh), has been linked to risk-taking behavior and implicated in reward seeking and evaluation. Most neurons in the NAc are medium spiny neurons (MSNs) that express dopamine D1 receptors (D1R +) and/or dopamine D2 receptors (D2R +). Changes in dopaminergic and glutamatergic systems occur during adolescence and converge in the NAc. While there are previous investigations into sex differences in membrane excitability and synaptic glutamate transmission in both subdivisions of the NAc, to our knowledge, none have specified NAcSh D1R + MSNs from mice during pre- and mid-adolescence. METHODS Sagittal brain slices containing the NAc were prepared from B6.Cg-Tg(Drd1a-tdTomato)6Calak/J mice of both sexes from postnatal days 21-25 and 35-47, representing pre- and mid-adolescence, respectively. Whole-cell electrophysiology recordings were collected from NAcSh D1R + MSNs in the form of membrane-voltage responses to current injections, to assess membrane properties and action potential waveform characteristics, and spontaneous excitatory postsynaptic currents (sEPSCs) to assess glutamatergic synaptic activity. RESULTS Relative to pre-adolescent males, pre-adolescent female NAcSh D1R + MSNs exhibited a less hyperpolarized resting membrane potential, increased input resistance, and smaller action potential afterhyperpolarization amplitudes. During mid-adolescence, decreased input resistance and a shorter action potential duration in females were the only sex differences observed. CONCLUSIONS Taken together, our results indicate that NAcSh D1R + MSNs in mice exhibit sex differences in membrane properties and AP waveform during pre-adolescence that are overall indicative of increased cellular excitability in females and are suggestive of possible sex differences in glycine receptors, inwardly-rectifying potassium channels, and large conductance voltage-gated potassium channels. These differences do not appear to persist into mid-adolescence, when sex was observed to affect input resistance oppositely to that of pre-adolescence and AP waveform in a manner suggestive of differences in voltage-gated potassium channels.
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Affiliation(s)
- Heather C Aziz
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 2409 University Avenue, Austin, TX, 78712, USA.
| | - Regina A Mangieri
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 2409 University Avenue, Austin, TX, 78712, USA
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2
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Gallagher CI, Frangos ZJ, Sheipouri D, Shimmon S, Duman MN, Jayakumar S, Cioffi CL, Rawling T, Vandenberg RJ. Novel Phenylene Lipids That Are Positive Allosteric Modulators of Glycine Receptors and Inhibitors of Glycine Transporter 2. ACS Chem Neurosci 2023; 14:2634-2647. [PMID: 37466545 DOI: 10.1021/acschemneuro.3c00167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023] Open
Abstract
Chronic pain is a complex condition that remains resistant to current therapeutics. We previously synthesized a series of N-acyl amino acids (NAAAs) that inhibit the glycine transporter, GlyT2, some of which are also positive allosteric modulators of glycine receptors (GlyRs). In this study, we have synthesized a library of NAAAs that contain a phenylene ring within the acyl tail with the objective of improving efficacy at both GlyT2 and GlyRs and also identifying compounds that are efficacious as dual-acting modulators to enhance glycine neurotransmission. The most efficacious positive allosteric modulator of GlyRs was 2-[8-(2-octylphenyl)octanoylamino]acetic acid (8-8 OPGly) which potentiates the EC5 for glycine activation of GlyRα1 by 1500% with an EC50 of 664 nM. Phenylene-containing NAAAs with a lysine headgroup were the most potent inhibitors of GlyT2 with (2S)-6-amino-2-[8-(3-octylphenyl)octanoylamino]hexanoic acid (8-8 MPLys) inhibiting GlyT2 with an IC50 of 32 nM. The optimal modulator across both proteins was (2S)-6-amino-2-[8-(2-octylphenyl)octanoylamino]hexanoic acid (8-8 OPLys), which inhibits GlyT2 with an IC50 of 192 nM and potentiates GlyRs by up to 335% at 1 μM. When tested in a dual GlyT2/GlyRα1 expression system, 8-8 OPLys caused the greatest reductions in the EC50 for glycine. This suggests that the synergistic effects of a dual-acting modulator cause greater enhancements in glycinergic activity compared to single-target modulators and may provide an alternate approach to the development of new non-opioid analgesics for the treatment of chronic pain.
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Affiliation(s)
- Casey I Gallagher
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Zachary J Frangos
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Diba Sheipouri
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Meryem-Nur Duman
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Srinivasan Jayakumar
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Christopher L Cioffi
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180, United States
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, Faculty of Science, The University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Robert J Vandenberg
- Molecular and Cellular Biomedicine Theme, School of Medical Sciences, University of Sydney, Sydney, NSW 2006, Australia
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Fogarty MJ. Inhibitory Synaptic Influences on Developmental Motor Disorders. Int J Mol Sci 2023; 24:ijms24086962. [PMID: 37108127 PMCID: PMC10138861 DOI: 10.3390/ijms24086962] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 04/05/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
During development, GABA and glycine play major trophic and synaptic roles in the establishment of the neuromotor system. In this review, we summarise the formation, function and maturation of GABAergic and glycinergic synapses within neuromotor circuits during development. We take special care to discuss the differences in limb and respiratory neuromotor control. We then investigate the influences that GABAergic and glycinergic neurotransmission has on two major developmental neuromotor disorders: Rett syndrome and spastic cerebral palsy. We present these two syndromes in order to contrast the approaches to disease mechanism and therapy. While both conditions have motor dysfunctions at their core, one condition Rett syndrome, despite having myriad symptoms, has scientists focused on the breathing abnormalities and their alleviation-to great clinical advances. By contrast, cerebral palsy remains a scientific quagmire or poor definitions, no widely adopted model and a lack of therapeutic focus. We conclude that the sheer abundance of diversity of inhibitory neurotransmitter targets should provide hope for intractable conditions, particularly those that exhibit broad spectra of dysfunction-such as spastic cerebral palsy and Rett syndrome.
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Affiliation(s)
- Matthew J Fogarty
- Department of Physiology & Biomedical Engineering, Mayo Clinic, Rochester, MN 55902, USA
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4
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Miranda CO, Hegedüs K, Kis G, Antal M. Synaptic Targets of Glycinergic Neurons in Laminae I-III of the Spinal Dorsal Horn. Int J Mol Sci 2023; 24:ijms24086943. [PMID: 37108107 PMCID: PMC10139066 DOI: 10.3390/ijms24086943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/04/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
A great deal of evidence supports the inevitable importance of spinal glycinergic inhibition in the development of chronic pain conditions. However, it remains unclear how glycinergic neurons contribute to the formation of spinal neural circuits underlying pain-related information processing. Thus, we intended to explore the synaptic targets of spinal glycinergic neurons in the pain processing region (laminae I-III) of the spinal dorsal horn by combining transgenic technology with immunocytochemistry and in situ hybridization accompanied by light and electron microscopy. First, our results suggest that, in addition to neurons in laminae I-III, glycinergic neurons with cell bodies in lamina IV may contribute substantially to spinal pain processing. On the one hand, we show that glycine transporter 2 immunostained glycinergic axon terminals target almost all types of excitatory and inhibitory interneurons identified by their neuronal markers in laminae I-III. Thus, glycinergic postsynaptic inhibition, including glycinergic inhibition of inhibitory interneurons, must be a common functional mechanism of spinal pain processing. On the other hand, our results demonstrate that glycine transporter 2 containing axon terminals target only specific subsets of axon terminals in laminae I-III, including nonpeptidergic nociceptive C fibers binding IB4 and nonnociceptive myelinated A fibers immunoreactive for type 1 vesicular glutamate transporter, indicating that glycinergic presynaptic inhibition may be important for targeting functionally specific subpopulations of primary afferent inputs.
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Affiliation(s)
- Camila Oliveira Miranda
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Krisztina Hegedüs
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Gréta Kis
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
| | - Miklós Antal
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, H-4032 Debrecen, Hungary
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5
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Gradwell MA, Smith KM, Dayas CV, Smith DW, Hughes DI, Callister RJ, Graham BA. Altered Intrinsic Properties and Inhibitory Connectivity in Aged Parvalbumin-Expressing Dorsal Horn Neurons. Front Neural Circuits 2022; 16:834173. [PMID: 35874431 PMCID: PMC9305305 DOI: 10.3389/fncir.2022.834173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 06/15/2022] [Indexed: 11/13/2022] Open
Abstract
The incidence of pain symptoms such as allodynia are known to increase with age. Parvalbumin expressing interneurons (PVINs) within the dorsal horn (DH) of the spinal cord play an important role in allodynia whereby their inhibitory connections prevent innocuous touch information from exciting nociceptive pathways. Here we ask whether the functional properties of PVINs are altered by aging, comparing their functional properties in adult (3–7 month) and aged mice (23–28 month). Patch clamp recordings were made from PVINs in laminae IIi-III of parasagittal spinal cord slices. The intrinsic excitability of PVINs changed with age. Specifically, AP discharge shifted from initial bursting to tonic firing, and firing duration during current injection increased. The nature of excitatory synaptic input to PVINs also changed with age with larger but less frequent spontaneous excitatory currents occurring in aged mice, however, the net effect of these differences produced a similar level of overall excitatory drive. Inhibitory drive was also remarkably similar in adult and aged PVINs. Photostimulation of ChR2 expressing PVINs was used to study inhibitory connections between PVINs and unidentified DH neurons and other PVINs. Based on latency and jitter, monosynaptic PVIN to unidentified-cell and PVIN-PVIN connections were compared in adult and aged mice, showing that PVIN to unidentified-cell connection strength increased with age. Fitting single or double exponentials to the decay phase of IPSCs showed there was also a shift from mixed (glycinergic and GABAergic) to GABAergic inhibitory transmission in aged animals. Overall, our data suggest the properties of PVIN neurons in aged animals enhance their output in spinal circuits in a manner that would blunt allodynia and help maintain normal sensory experience during aging.
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Affiliation(s)
- Mark A. Gradwell
- Rutgers, The State University of New Jersey, New Brunswick, NJ, United States
| | - Kelly M. Smith
- Centre for Neuroscience, Science Tower, University of Pittsburgh, Pittsburgh, PA, United States
| | - Christopher V. Dayas
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia
- Brain Neuromodulation Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - Douglas W. Smith
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia
- Brain Neuromodulation Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - David I. Hughes
- Institute of Neuroscience Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Robert J. Callister
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia
- Brain Neuromodulation Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - Brett A. Graham
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia
- Brain Neuromodulation Research Program, Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
- *Correspondence: Brett A. Graham,
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Oliva CA, Stehberg J, Barra R, Mariqueo T. Neuropathic Pain Induces Interleukin-1β Sensitive Bimodal Glycinergic Activity in the Central Amygdala. Int J Mol Sci 2022; 23:ijms23137356. [PMID: 35806360 PMCID: PMC9266833 DOI: 10.3390/ijms23137356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 06/26/2022] [Accepted: 06/28/2022] [Indexed: 02/04/2023] Open
Abstract
Neuropathic pain reduces GABA and glycine receptor (GlyR)-mediated activity in spinal and supraspinal regions associated with pain processing. Interleukin-1β (IL-1β) alters Central Amygdala (CeA) excitability by reducing glycinergic inhibition in a mechanism that involves the auxiliary β-subunit of GlyR (βGlyR), which is highly expressed in this region. However, GlyR activity and its modulation by IL-1β in supraspinal brain regions under neuropathic pain have not been studied. We performed chronic constriction injury (CCI) of the sciatic nerve in male Sprague Dawley rats, a procedure that induces hind paw plantar hyperalgesia and neuropathic pain. Ten days later, the rats were euthanized, and their brains were sliced. Glycinergic spontaneous inhibitory currents (sIPSCs) were recorded in the CeA slices. The sIPSCs from CeA neurons of CCI animals show a bimodal amplitude distribution, different from the normal distribution in Sham animals, with small and large amplitudes of similar decay constants. The perfusion of IL-1β (10 ng/mL) in these slices reduced the amplitudes within the first five minutes, with a pronounced effect on the largest amplitudes. Our data support a possible role for CeA GlyRs in pain processing and in the neuroimmune modulation of pain perception.
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Affiliation(s)
- Carolina A. Oliva
- Facultad de Educación, Universidad de Las Américas, República 71, Santiago 8370040, Chile
- Correspondence: (C.A.O.); (T.M.)
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andrés Bello, República 330, Santiago 8370186, Chile;
| | - Rafael Barra
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3677, Santiago 8320000, Chile;
| | - Trinidad Mariqueo
- Laboratorio de Neurofarmacología, Centro de Investigaciones Médicas, Facultad de Medicina, Universidad de Talca, Av. Lircay S/N, Talca 3460000, Chile
- Correspondence: (C.A.O.); (T.M.)
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7
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Paulsen RT, Burrell BD. Activity-Dependent Modulation of Tonic GABA Currents by Endocannabinoids in Hirudo verbana. Front Synaptic Neurosci 2022; 14:760330. [PMID: 35368247 PMCID: PMC8964407 DOI: 10.3389/fnsyn.2022.760330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 02/21/2022] [Indexed: 01/21/2023] Open
Abstract
Endocannabinoids are lipid neuromodulators that are synthesized on demand and primarily signal in a retrograde manner to elicit depression of excitatory and inhibitory synapses. Despite the considerable interest in their potential analgesic effects, there is evidence that endocannabinoids can have both pro-nociceptive and anti-nociceptive effects. The mechanisms contributing to the opposing effects of endocannabinoids in nociception need to be better understood before cannabinoid-based therapies can be effectively utilized to treat pain. Using the medicinal leech, Hirudo verbana, this work investigates whether endocannabinoids modulate tonic inhibition onto non-nociceptive afferents. In voltage clamp recordings, we analyzed changes in the tonic inhibition in pressure-sensitive (P) cells following pre-treatment with endocannabinoids, 2-arachidonoylglycerol (2-AG) or anandamide (AEA). We also tested whether high frequency stimulation (HFS) of nociceptive (N) cells could also modulate tonic inhibition. Both endocannabinoid application and N cell HFS depressed tonic inhibition in the P cell. Depression of tonic inhibition by N cell HFS was blocked by SB 366791 (a TRPV1 inhibitor). SB 366791 also prevented 2-AG-and AEA-induced depression of tonic inhibition. HFS-induced depression was not blocked by tetrahydrolipstatin (THL), which prevents 2-AG synthesis, nor AM 251 (a CB1 receptor inverse agonist). These results illustrate a novel activity-dependent modulation of tonic GABA currents that is mediated by endocannabinoid signaling and is likely to play an important role in sensitization of non-nociceptive afferent pathways.
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8
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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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9
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Muñoz B, Mariqueo T, Murath P, Peters C, Yevenes GE, Moraga-Cid G, Peoples RW, Aguayo LG. Modulatory Actions of the Glycine Receptor β Subunit on the Positive Allosteric Modulation of Ethanol in α2 Containing Receptors. Front Mol Neurosci 2021; 14:763868. [PMID: 34867189 PMCID: PMC8637530 DOI: 10.3389/fnmol.2021.763868] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/18/2021] [Indexed: 01/23/2023] Open
Abstract
Alpha1-containing glycine receptors (GlyRs) are major mediators of synaptic inhibition in the spinal cord and brain stem. Recent studies reported the presence of α2-containing GlyRs in other brain regions, such as nucleus accumbens and cerebral cortex. GlyR activation decreases neuronal excitability associated with sensorial information, motor control, and respiratory functions; all of which are significantly altered during ethanol intoxication. We evaluated the role of β GlyR subunits and of two basic amino acid residues, K389 and R390, located in the large intracellular loop (IL) of the α2 GlyR subunit, which are important for binding and functional modulation by Gβγ, the dimer of the trimeric G protein conformation, using HEK-293 transfected cells combined with patch clamp electrophysiology. We demonstrate a new modulatory role of the β subunit on ethanol sensitivity of α2 subunits. Specifically, we found a differential allosteric modulation in homomeric α2 GlyRs compared with the α2β heteromeric conformation. Indeed, while α2 was insensitive, α2β GlyRs were substantially potentiated by ethanol, GTP-γ-S, propofol, Zn2+ and trichloroethanol. Furthermore, a Gβγ scavenger (ct-GRK2) selectively attenuated the effects of ethanol on recombinant α2β GlyRs. Mutations in an α2 GlyR co-expressed with the β subunit (α2AAβ) specifically blocked ethanol sensitivity, but not propofol potentiation. These results show a selective mechanism for low ethanol concentration effects on homomeric and heteromeric conformations of α2 GlyRs and provide a new mechanism for ethanol pharmacology, which is relevant to upper brain regions where α2 GlyRs are abundantly expressed.
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Affiliation(s)
- Braulio Muñoz
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Trinidad Mariqueo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Pablo Murath
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Christian Peters
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | - Gonzalo E Yevenes
- Laboratory of Neuropharmacology, Department of Physiology, Universidad de Concepción, Concepción, Chile
| | | | - Robert W Peoples
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, United States
| | - Luis G Aguayo
- Laboratory of Neurophysiology, Department of Physiology, Universidad de Concepción, Concepción, Chile
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10
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Spinal Inhibitory Interneurons: Gatekeepers of Sensorimotor Pathways. Int J Mol Sci 2021; 22:ijms22052667. [PMID: 33800863 PMCID: PMC7961554 DOI: 10.3390/ijms22052667] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 02/26/2021] [Accepted: 03/04/2021] [Indexed: 12/20/2022] Open
Abstract
The ability to sense and move within an environment are complex functions necessary for the survival of nearly all species. The spinal cord is both the initial entry site for peripheral information and the final output site for motor response, placing spinal circuits as paramount in mediating sensory responses and coordinating movement. This is partly accomplished through the activation of complex spinal microcircuits that gate afferent signals to filter extraneous stimuli from various sensory modalities and determine which signals are transmitted to higher order structures in the CNS and to spinal motor pathways. A mechanistic understanding of how inhibitory interneurons are organized and employed within the spinal cord will provide potential access points for therapeutics targeting inhibitory deficits underlying various pathologies including sensory and movement disorders. Recent studies using transgenic manipulations, neurochemical profiling, and single-cell transcriptomics have identified distinct populations of inhibitory interneurons which express an array of genetic and/or neurochemical markers that constitute functional microcircuits. In this review, we provide an overview of identified neural components that make up inhibitory microcircuits within the dorsal and ventral spinal cord and highlight the importance of inhibitory control of sensorimotor pathways at the spinal level.
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11
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Solorza J, Oliva CA, Castillo K, Amestica G, Maldifassi MC, López-Cortés XA, Barra R, Stehberg J, Piesche M, Sáez-Briones P, González W, Arenas-Salinas M, Mariqueo TA. Effects of Interleukin-1β in Glycinergic Transmission at the Central Amygdala. Front Pharmacol 2021; 12:613105. [PMID: 33746753 PMCID: PMC7973117 DOI: 10.3389/fphar.2021.613105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 01/19/2021] [Indexed: 01/22/2023] Open
Abstract
Interleukin-1β (IL-1β) is an important cytokine that modulates peripheral and central pain sensitization at the spinal level. Among its effects, it increases spinal cord excitability by reducing inhibitory Glycinergic and GABAergic neurotransmission. In the brain, IL-1β is released by glial cells in regions associated with pain processing during neuropathic pain. It also has important roles in neuroinflammation and in regulating NMDA receptor activity required for learning and memory. The modulation of glycine-mediated inhibitory activity via IL-1β may play a critical role in the perception of different levels of pain. The central nucleus of the amygdala (CeA) participates in receiving and processing pain information. Interestingly, this nucleus is enriched in the regulatory auxiliary glycine receptor (GlyR) β subunit (βGlyR); however, no studies have evaluated the effect of IL-1β on glycinergic neurotransmission in the brain. Hence, we hypothesized that IL-1β may modulate GlyR-mediated inhibitory activity via interactions with the βGlyR subunit. Our results show that the application of IL-1β (10 ng/ml) to CeA brain slices has a biphasic effect; transiently increases and then reduces sIPSC amplitude of CeA glycinergic currents. Additionally, we performed molecular docking, site-directed mutagenesis, and whole-cell voltage-clamp electrophysiological experiments in HEK cells transfected with GlyRs containing different GlyR subunits. These data indicate that IL-1β modulates GlyR activity by establishing hydrogen bonds with at least one key amino acid residue located in the back of the loop C at the ECD domain of the βGlyR subunit. The present results suggest that IL-1β in the CeA controls glycinergic neurotransmission, possibly via interactions with the βGlyR subunit. This effect could be relevant for understanding how IL-1β released by glia modulates central processing of pain, learning and memory, and is involved in neuroinflammation.
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Affiliation(s)
- Jocelyn Solorza
- Center for Medical Research, Laboratory of Neuropharmacology, School of Medicine, Universidad de Talca, Talca, Chile.,Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - Carolina A Oliva
- Institute of Biomedical Sciences, Faculty of Medicine, Universidad Andrés Bello, Santiago, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Gabriela Amestica
- Center for Medical Research, Laboratory of Neuropharmacology, School of Medicine, Universidad de Talca, Talca, Chile
| | - María Constanza Maldifassi
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Xaviera A López-Cortés
- Department of Computer Science and Industries, Faculty of Engineering Science, Universidad Católica del Maule, Talca, Chile
| | - Rafael Barra
- Centro de Investigación Biomédica y Aplicada (CIBAP), Escuela de Medicina, Facultad de Ciencias Médicas, Universidad de Santiago de Chile (USACH), Santiago, Chile
| | - Jimmy Stehberg
- Faculty of Biological Sciences and Faculty of Medicine, Instituto de Ciencias Biomédicas, Universidad Andres Bello, Santiago, Chile
| | - Matthias Piesche
- Laboratory of Biomedical Research, Medicine Faculty, Universidad Católica del Maule, Talca, Chile.,Oncology Center, Medicine Faculty, Universidad Católica del Maule, Talca, Chile
| | - Patricio Sáez-Briones
- Laboratory of Neuropharmacology and Behavior, School of Medicine, Faculty of Medical Sciences, Universidad de Santiago de Chile (USACH), Santiago, Chile
| | - Wendy González
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Talca, Talca, Chile
| | - Mauricio Arenas-Salinas
- Centro de Bioinformática, Simulación y Modelado (CBSM), Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - Trinidad A Mariqueo
- Center for Medical Research, Laboratory of Neuropharmacology, School of Medicine, Universidad de Talca, Talca, Chile
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12
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Granier C, Schwarting J, Fourli E, Laage-Gaupp F, Hennrich AA, Schmalz A, Jacobi A, Wesolowski M, Conzelmann KK, Bareyre FM. Formation of somatosensory detour circuits mediates functional recovery following dorsal column injury. Sci Rep 2020; 10:10953. [PMID: 32616790 PMCID: PMC7331809 DOI: 10.1038/s41598-020-67866-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 06/15/2020] [Indexed: 11/15/2022] Open
Abstract
Anatomically incomplete spinal cord injuries can be followed by functional recovery mediated, in part, by the formation of intraspinal detour circuits. Here, we show that adult mice recover tactile and proprioceptive function following a unilateral dorsal column lesion. We therefore investigated the basis of this recovery and focused on the plasticity of the dorsal column-medial lemniscus pathway. We show that ascending dorsal root ganglion (DRG) axons branch in the spinal grey matter and substantially increase the number of these collaterals following injury. These sensory fibers exhibit synapsin-positive varicosities, indicating their integration into spinal networks. Using a monosynaptic circuit tracing with rabies viruses injected into the cuneate nucleus, we show the presence of spinal cord neurons that provide a detour pathway to the original target area of DRG axons. Notably the number of contacts between DRG collaterals and those spinal neurons increases by more than 300% after injury. We then characterized these interneurons and showed that the lesion triggers a remodeling of the connectivity pattern. Finally, using re-lesion experiments after initial remodeling of connections, we show that these detour circuits are responsible for the recovery of tactile and proprioceptive function. Taken together our study reveals that detour circuits represent a common blueprint for axonal rewiring after injury.
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Affiliation(s)
- Charlène Granier
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany.,Graduate School of Systemic Neurosciences, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Julian Schwarting
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Evangelia Fourli
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Fabian Laage-Gaupp
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Alexandru A Hennrich
- Max Von Pettenkofer-Institute, Virology, Faculty of Medicine, and Gene Center, LMU Munich, 80336, Munich, Germany
| | - Anja Schmalz
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Anne Jacobi
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Marta Wesolowski
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany.,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany.,Graduate School of Systemic Neurosciences, LMU Munich, 82152, Planegg-Martinsried, Germany
| | - Karl Klaus Conzelmann
- Max Von Pettenkofer-Institute, Virology, Faculty of Medicine, and Gene Center, LMU Munich, 80336, Munich, Germany
| | - Florence M Bareyre
- Institute of Clinical Neuroimmunology, University Hospital, LMU Munich, 81377, Munich, Germany. .,Biomedical Center Munich (BMC), Faculty of Medicine, LMU Munich, 82152, Planegg-Martinsried, Germany. .,Munich Cluster of Systems Neurology (SyNergy), 81377, Munich, Germany.
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13
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Nakamura M, Jang IS, Yamaga T, Kotani N, Akaike N. Effects of nitrous oxide on glycinergic transmission in rat spinal neurons. Brain Res Bull 2020; 162:191-198. [PMID: 32599127 DOI: 10.1016/j.brainresbull.2020.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 06/16/2020] [Accepted: 06/22/2020] [Indexed: 11/19/2022]
Abstract
We investigated the effects of nitrous oxide (N2O) on glycinergic inhibitory whole-cell and synaptic responses using a "synapse bouton preparation," dissociated mechanically from rat spinal sacral dorsal commissural nucleus (SDCN) neurons. This technique can evaluate pure single- or multi-synaptic responses from native functional nerve endings and enable us to accurately quantify how N2O influences pre- and postsynaptic transmission. We found that 70 % N2O enhanced exogenous glycine-induced whole-cell currents (IGly) at glycine concentrations lower than 3 × 10-5 M, but did not affect IGly at glycine concentrations higher than 10-4 M. N2O did not affect the amplitude and 1/e decay-time of both spontaneous and miniature glycinergic inhibitory postsynaptic currents recorded in the absence and presence of tetrodotoxin (sIPSCs and mIPSCs, respectively). The decrease in frequency induced by N2O was observed in sIPSCs but not in mIPSCs, which was recorded in the presence of both tetrodotoxin and Cd2+, which block voltage-gated Na+ and Ca2+ channels, respectively. N2O also decreased the amplitude and increased the failure rate and paired-pulse ratio of action potential-evoked glycinergic inhibitory postsynaptic currents. N2O slightly decreased the Ba2+ currents mediated by voltage-gated Ca2+ channels in SDCN neurons. We found that N2O suppresses glycinergic responses at synaptic levels with presynaptic effect having much more predominant role. The difference between glycinergic whole-cell and synaptic responses suggests that extrasynaptic responses seriously modulate whole-cell currents. Our results strongly suggest that these responses may thus in part explain analgesic effects of N2O via marked glutamatergic inhibition by glycinergic responses in the spinal cord.
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Affiliation(s)
- Michiko Nakamura
- Department of Pharmacology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea
| | - Il-Sung Jang
- Department of Pharmacology, School of Dentistry, Kyungpook National University, 2177 Dalgubeol-daero, Jung-gu, Daegu, 700-412, Republic of Korea
| | - Toshitaka Yamaga
- Research Division for Life Science, Kumamoto Health Science University, 325 Izumi-machi, Kita-ku, Kumamoto 861-5598, Japan
| | - Naoki Kotani
- Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, Saitama 343-0821, Japan
| | - Norio Akaike
- Research Division of Neurophysiology, Kitamoto Hospital, 3-7-6 Kawarasone, Koshigaya, Saitama 343-0821, Japan; Research Division for Clinical Pharmacology, Medical Corporation, Juryo Group, Kumamoto Kinoh Hospital, 6-8-1 Yamamuro, Kita-ku, Kumamoto 860-8518, Japan.
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14
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Mayhew JA, Callister RJ, Walker FR, Smith DW, Graham BA. Aging alters signaling properties in the mouse spinal dorsal horn. Mol Pain 2020; 15:1744806919839860. [PMID: 30845881 PMCID: PMC6537084 DOI: 10.1177/1744806919839860] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A well-recognized relationship exists between aging and increased susceptibility
to chronic pain conditions, underpinning the view that pain signaling pathways
differ in aged individuals. Yet despite the higher prevalence of altered pain
states among the elderly, the majority of preclinical work studying mechanisms
of aberrant sensory processing are conducted in juvenile or young adult animals.
This mismatch is especially true for electrophysiological studies where patch
clamp recordings from aged tissue are generally viewed as particularly
challenging. In this study, we have undertaken an electrophysiological
characterization of spinal dorsal horn neurons in young adult (3–4 months) and
aged (28–32 months) mice. We show that patch clamp data can be routinely
acquired in spinal cord slices prepared from aged animals and that the
excitability properties of aged dorsal horn neurons differ from recordings in
tissue prepared from young animals. Specifically, aged dorsal horn neurons more
readily exhibit repetitive action potential discharge, indicative of a more
excitable phenotype. This observation was accompanied by a decrease in the
amplitude and charge of spontaneous excitatory synaptic input to dorsal horn
neurons and an increase in the contribution of GABAergic signaling to
spontaneous inhibitory synaptic input in aged recordings. While the functional
significance of these altered circuit properties remains to be determined,
future work should seek to assess whether such features may render the aged
dorsal horn more susceptible to aberrant injury or disease-induced signaling and
contribute to increased pain in the elderly.
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Affiliation(s)
- J A Mayhew
- 1 Faculty of Health, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.,2 Hunter Medical Research Institute, New Lambton Heights, Australia
| | - R J Callister
- 1 Faculty of Health, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.,2 Hunter Medical Research Institute, New Lambton Heights, Australia
| | - F R Walker
- 1 Faculty of Health, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.,2 Hunter Medical Research Institute, New Lambton Heights, Australia
| | - D W Smith
- 1 Faculty of Health, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.,2 Hunter Medical Research Institute, New Lambton Heights, Australia
| | - B A Graham
- 1 Faculty of Health, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, Australia.,2 Hunter Medical Research Institute, New Lambton Heights, Australia
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15
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Madden JF, Davis OC, Boyle KA, Iredale JA, Browne TJ, Callister RJ, Smith DW, Jobling P, Hughes DI, Graham BA. Functional and Molecular Analysis of Proprioceptive Sensory Neuron Excitability in Mice. Front Mol Neurosci 2020; 13:36. [PMID: 32477061 PMCID: PMC7232575 DOI: 10.3389/fnmol.2020.00036] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 02/20/2020] [Indexed: 12/22/2022] Open
Abstract
Neurons located in dorsal root ganglia (DRG) are crucial for transmitting peripheral sensations such as proprioception, touch, temperature, and nociception to the spinal cord before propagating these signals to higher brain structures. To date, difficulty in identifying modality-specific DRG neurons has limited our ability to study specific populations in detail. As the calcium-binding protein parvalbumin (PV) is a neurochemical marker for proprioceptive DRG cells we used a transgenic mouse line expressing green fluorescent protein (GFP) in PV positive DRGs, to study the functional and molecular properties of putative proprioceptive neurons. Immunolabeled DRGs showed a 100% overlap between GFP positive (GFP+) and PV positive cells, confirming the PVeGFP mouse accurately labeled PV neurons. Targeted patch-clamp recording from isolated GFP+ and GFP negative (GFP−) neurons showed the passive membrane properties of the two groups were similar, however, their active properties differed markedly. All GFP+ neurons fired a single spike in response to sustained current injection and their action potentials (APs) had faster rise times, lower thresholds and shorter half widths. A hyperpolarization-activated current (Ih) was observed in all GFP+ neurons but was infrequently noted in the GFP− population (100% vs. 11%). For GFP+ neurons, Ih activation rates varied markedly, suggesting differences in the underlying hyperpolarization-activated cyclic nucleotide-gated channel (HCN) subunit expression responsible for the current kinetics. Furthermore, quantitative polymerase chain reaction (qPCR) showed the HCN subunits 2, 1, and 4 mRNA (in that order) was more abundant in GFP+ neurons, while HCN 3 was more highly expressed in GFP− neurons. Likewise, immunolabeling confirmed HCN 1, 2, and 4 protein expression in GFP+ neurons. In summary, certain functional properties of GFP+ and GFP− cells differ markedly, providing evidence for modality-specific signaling between the two groups. However, the GFP+ DRG population demonstrates considerable internal heterogeneity when hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel) properties and subunit expression are considered. We propose this heterogeneity reflects the existence of different peripheral receptors such as tendon organs, muscle spindles or mechanoreceptors in the putative proprioceptive neuron population.
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Affiliation(s)
- Jessica F Madden
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - Olivia C Davis
- Institute of Neuroscience Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Kieran A Boyle
- Institute of Neuroscience Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jacqueline A Iredale
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - Tyler J Browne
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - Robert J Callister
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - Douglas W Smith
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - Phillip Jobling
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - David I Hughes
- Institute of Neuroscience Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Brett A Graham
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW, Australia.,Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
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16
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Moraga-Cid G, San Martín VP, Lara CO, Muñoz B, Marileo AM, Sazo A, Muñoz-Montesino C, Fuentealba J, Castro PA, Guzmán L, Burgos CF, Zeilhofer HU, Aguayo LG, Corringer PJ, Yévenes GE. Modulation of glycine receptor single-channel conductance by intracellular phosphorylation. Sci Rep 2020; 10:4804. [PMID: 32179786 PMCID: PMC7076024 DOI: 10.1038/s41598-020-61677-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 02/12/2020] [Indexed: 01/05/2023] Open
Abstract
Glycine receptors (GlyRs) are anion-permeable pentameric ligand-gated ion channels (pLGICs). The GlyR activation is critical for the control of key neurophysiological functions, such as motor coordination, respiratory control, muscle tone and pain processing. The relevance of the GlyR function is further highlighted by the presence of abnormal glycinergic inhibition in many pathophysiological states, such as hyperekplexia, epilepsy, autism and chronic pain. In this context, previous studies have shown that the functional inhibition of GlyRs containing the α3 subunit is a pivotal mechanism of pain hypersensitivity. This pathway involves the activation of EP2 receptors and the subsequent PKA-dependent phosphorylation of α3GlyRs within the intracellular domain (ICD), which decrease the GlyR-associated currents and enhance neuronal excitability. Despite the importance of this mechanism of glycinergic dis-inhibition associated with dysfunctional α3GlyRs, our current understanding of the molecular events involved is limited. Here, we report that the activation of PKA signaling pathway decreases the unitary conductance of α3GlyRs. We show in addition that the substitution of the PKA-targeted serine with a negatively charged residue within the ICD of α3GlyRs and of chimeric receptors combining bacterial GLIC and α3GlyR was sufficient to generate receptors with reduced conductance. Thus, our findings reveal a potential biophysical mechanism of glycinergic dis-inhibition and suggest that post-translational modifications of the ICD, such as phosphorylation, may shape the conductance of other pLGICs.
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Affiliation(s)
- Gustavo Moraga-Cid
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile.
| | - Victoria P San Martín
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Cesar O Lara
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Braulio Muñoz
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Ana M Marileo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Anggelo Sazo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Carola Muñoz-Montesino
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Jorge Fuentealba
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Patricio A Castro
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Leonardo Guzmán
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Carlos F Burgos
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | - Hanns U Zeilhofer
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland.,Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Vladimir-Prelog-Weg 1-5/10, CH-8090, Zurich, Switzerland
| | - Luis G Aguayo
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile
| | | | - Gonzalo E Yévenes
- Department of Physiology, Faculty of Biological Sciences, University of Concepción, Concepción, Chile.
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17
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Lee KY, Ratté S, Prescott SA. Excitatory neurons are more disinhibited than inhibitory neurons by chloride dysregulation in the spinal dorsal horn. eLife 2019; 8:e49753. [PMID: 31742556 PMCID: PMC6887484 DOI: 10.7554/elife.49753] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 11/18/2019] [Indexed: 01/22/2023] Open
Abstract
Neuropathic pain is a debilitating condition caused by the abnormal processing of somatosensory input. Synaptic inhibition in the spinal dorsal horn plays a key role in that processing. Mechanical allodynia - the misperception of light touch as painful - occurs when inhibition is compromised. Disinhibition is due primarily to chloride dysregulation caused by hypofunction of the potassium-chloride co-transporter KCC2. Here we show, in rats, that excitatory neurons are disproportionately affected. This is not because chloride is differentially dysregulated in excitatory and inhibitory neurons, but, rather, because excitatory neurons rely more heavily on inhibition to counterbalance strong excitation. Receptive fields in both cell types have a center-surround organization but disinhibition unmasks more excitatory input to excitatory neurons. Differences in intrinsic excitability also affect how chloride dysregulation affects spiking. These results deepen understanding of how excitation and inhibition are normally balanced in the spinal dorsal horn, and how their imbalance disrupts somatosensory processing.
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Affiliation(s)
- Kwan Yeop Lee
- Neurosciences and Mental HealthThe Hospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
- Institute of Biomaterials and Biomedical EngineeringUniversity of TorontoTorontoCanada
| | - Stéphanie Ratté
- Neurosciences and Mental HealthThe Hospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
- Institute of Biomaterials and Biomedical EngineeringUniversity of TorontoTorontoCanada
| | - Steven A Prescott
- Neurosciences and Mental HealthThe Hospital for Sick ChildrenTorontoCanada
- Department of PhysiologyUniversity of TorontoTorontoCanada
- Institute of Biomaterials and Biomedical EngineeringUniversity of TorontoTorontoCanada
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18
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Gradwell MA, Callister RJ, Graham BA. Reviewing the case for compromised spinal inhibition in neuropathic pain. J Neural Transm (Vienna) 2019; 127:481-503. [PMID: 31641856 DOI: 10.1007/s00702-019-02090-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 09/30/2019] [Indexed: 12/20/2022]
Abstract
A striking and debilitating property of the nervous system is that damage to this tissue can cause chronic intractable pain, which persists long after resolution of the initial insult. This neuropathic form of pain can arise from trauma to peripheral nerves, the spinal cord, or brain. It can also result from neuropathies associated with disease states such as diabetes, human immunodeficiency virus/AIDS, herpes, multiple sclerosis, cancer, and chemotherapy. Regardless of the origin, treatments for neuropathic pain remain inadequate. This continues to drive research into the underlying mechanisms. While the literature shows that dysfunction in numerous loci throughout the CNS can contribute to chronic pain, the spinal cord and in particular inhibitory signalling in this region have remained major research areas. This review focuses on local spinal inhibition provided by dorsal horn interneurons, and how such inhibition is disrupted during the development and maintenance of neuropathic pain.
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Affiliation(s)
- M A Gradwell
- School of Biomedical Sciences and Pharmacy, Faculty of Health, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - R J Callister
- School of Biomedical Sciences and Pharmacy, Faculty of Health, University of Newcastle, Callaghan, NSW, 2308, Australia
- Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia
| | - B A Graham
- School of Biomedical Sciences and Pharmacy, Faculty of Health, University of Newcastle, Callaghan, NSW, 2308, Australia.
- Hunter Medical Research Institute (HMRI), New Lambton Heights, NSW, Australia.
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19
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Brandenburg JE, Fogarty MJ, Sieck GC. A Critical Evaluation of Current Concepts in Cerebral Palsy. Physiology (Bethesda) 2019; 34:216-229. [PMID: 30968751 PMCID: PMC7938766 DOI: 10.1152/physiol.00054.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 01/11/2019] [Accepted: 01/23/2019] [Indexed: 11/22/2022] Open
Abstract
Spastic cerebral palsy (CP), despite the name, is not consistently identifiable by specific brain lesions. CP animal models focus on risk factors for development of CP, yet few reproduce the diagnostic symptoms. Animal models of CP must advance beyond risk factors to etiologies, including both the brain and spinal cord.
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Affiliation(s)
- Joline E Brandenburg
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Matthew J Fogarty
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
| | - Gary C Sieck
- Department of Physical Medicine and Rehabilitation, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine , Rochester, Minnesota
- Department of Anesthesiology, Mayo Clinic College of Medicine , Rochester, Minnesota
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20
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Booker SA, Wyllie DJA. Parvalbumin interneurons in the dorsal horn: it's not all about GABA. J Physiol 2017; 595:7019-7020. [PMID: 29068060 DOI: 10.1113/jp275260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Sam A Booker
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK.,Patrick Wild Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - David J A Wyllie
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK.,Patrick Wild Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK.,Centre for Brain Development and Repair, Institute for Stem Cell Biology and Regenerative Medicine, National Centre for Biological Sciences, Bangalore, 560065, India
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