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Merighi A. The histology, physiology, neurochemistry and circuitry of the substantia gelatinosa Rolandi (lamina II) in mammalian spinal cord. Prog Neurobiol 2018; 169:91-134. [PMID: 29981393 DOI: 10.1016/j.pneurobio.2018.06.012] [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] [Received: 08/04/2017] [Revised: 06/07/2018] [Accepted: 06/30/2018] [Indexed: 02/06/2023]
Abstract
The substantia gelatinosa Rolandi (SGR) was first described about two centuries ago. In the following decades an enormous amount of information has permitted us to understand - at least in part - its role in the initial processing of pain and itch. Here, I will first provide a comprehensive picture of the histology, physiology, and neurochemistry of the normal SGR. Then, I will analytically discuss the SGR circuits that have been directly demonstrated or deductively envisaged in the course of the intensive research on this area of the spinal cord, with particular emphasis on the pathways connecting the primary afferent fibers and the intrinsic neurons. The perspective existence of neurochemically-defined sets of primary afferent neurons giving rise to these circuits will be also discussed, with the proposition that a cross-talk between different subsets of peptidergic fibers may be the structural and functional substrate of additional gating mechanisms in SGR. Finally, I highlight the role played by slow acting high molecular weight modulators in these gating mechanisms.
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Affiliation(s)
- Adalberto Merighi
- Department of Veterinary Sciences, University of Turin, Largo Paolo Braccini 2, I-10095 Grugliasco (TO), Italy.
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2
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Evanson NK, Herman JP. Role of Paraventricular Nucleus Glutamate Signaling in Regulation of HPA Axis Stress Responses. ACTA ACUST UNITED AC 2015; 21:253-260. [PMID: 26472933 DOI: 10.4036/iis.2015.b.10] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The hypothalamus-pituitary-adrenal (HPA) axis is the main neuroendocrine arm of the stress response, activation of which leads to the production of glucocorticoid hormones. Glucocorticoids are steroid hormones that are secreted from the adrenal cortex, and have a variety of effects on the body, including modulation of the immune system, suppression of reproductive hormones maintenance of blood glucose levels, and maintenance of blood pressure. Glutamate plays an important role in coordination of HPA axis output. There is strong evidence that glutamate drives HPA axis stress responses through excitatory signaling via ionotropic glutamate receptor signaling. However, glutamate signaling via kainate receptors and group I metabotropic receptors inhibit HPA drive, probably via presynaptic inhibitory mechanisms. Notably, kainate receptors are also localized in the median eminence, and appear to play an excitatory role in control of CRH release at the nerve terminals. Finally, glutamate innervation of the PVN undergoes neuroplastic changes under conditions of chronic stress, and may be involved in sensitization of HPA axis responses. Altogether, the data suggest that glutamate plays a complex role in excitation of CRH neurons, acting at multiple levels to both drive HPA axis responses and limit over-activation.
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Affiliation(s)
- Nathan K Evanson
- Cincinnati Children's Hospital Medical Center, Department of Pediatrics, Pediatric rehabilitation division. 3333 Burnet Ave, MLC 4009, Cincinnati, OH, USA. 45229
| | - James P Herman
- Department of Psychiatry, University of Cincinnati. 2170 E. Galbraith Road, Cincinnati, OH, USA. 45237
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Kannampalli P, Sengupta JN. Role of principal ionotropic and metabotropic receptors in visceral pain. J Neurogastroenterol Motil 2015; 21:147-58. [PMID: 25843070 PMCID: PMC4398235 DOI: 10.5056/jnm15026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 02/24/2015] [Accepted: 03/26/2015] [Indexed: 12/13/2022] Open
Abstract
Visceral pain is the most common form of pain caused by varied diseases and a major reason for patients to seek medical consultation. It also leads to a significant economic burden due to workdays lost and reduced productivity. Further, long-term use of non-specific medications is also associated with side effects affecting the quality of life. Despite years of extensive research and the availability of several therapeutic options, management of patients with chronic visceral pain is often inadequate, resulting in frustration for both patients and physicians. This is, most likely, because the mechanisms associated with chronic visceral pain are different from those of acute pain. Accumulating evidence from years of research implicates several receptors and ion channels in the induction and maintenance of central and peripheral sensitization during chronic pain states. Understanding the specific role of these receptors will facilitate to capitalize on their unique properties to augment the therapeutic efficacy while at the same time minimizing unwanted side effects. The aim of this review is to provide a concise review of the recent literature that reports on the role of principal ionotropic receptors and metabotropic receptors in the modulation visceral pain. We also include an overview of the possibility of these receptors as potential new targets for the treatment of chronic visceral pain conditions.
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Affiliation(s)
- Pradeep Kannampalli
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Jyoti N Sengupta
- Division of Gastroenterology and Hepatology, Medical College of Wisconsin, Milwaukee, WI, USA
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4
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Lauri S, Taira T. Kainate receptors in developing presynaptic terminals. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/wmts.3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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5
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Metabotropic actions of kainate receptors in dorsal root ganglion cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011. [PMID: 21713668 DOI: 10.1007/978-1-4419-9557-5_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
Kainate receptors are widely distributed in the CNS, but also in the PNS. Dorsal root ganglia are enriched in this subtype of glutamate ionotropic receptors. In addition to their activity as ligand-gated ion channels, kainate receptors exhibit other properties already characterized in other systems, such as hippocampus, i.e., their ability to induce a metabotropic cascade signalling, through G-protein and PKC activation. With a very similar actuation mechanism as formerly described in the CNS, kainate receptors in the DRG also present other differentiated features, such as the Ca(2+) channel blockade and a self-regulation property. The peculiarity of these neurons has served to progress the study of kainate receptors. Nevertheless, many other physiological functions of these receptors remain unclear, as does the related molecular nature of the metabotropic cascade and the involvement of this signalling pathway with sensory transmission of pain.
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Park SA, Park SJ, Han SK. Expression of KA1 kainate receptor subunit in the substantia gelatinosa of the trigeminal subnucleus caudalis in mice. J Vet Sci 2010; 11:299-304. [PMID: 21113098 PMCID: PMC2998740 DOI: 10.4142/jvs.2010.11.4.299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The KA1 kainate receptor (KAR) subunit in the substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been implicated in the processing of nociceptive information from the orofacial region. This study compared the expression of the KA1 KAR subunit in the SG of the Vc in juvenile, prepubescent and adult mice. RT-PCR, Western blot and immunohistochemistry analyses were used to examine the expression level in SG area. The expression levels of the KA1 KAR subunit mRNA and protein were higher in juvenile mice than in prepubescent or adult mice. Quantitative data revealed that the KA1 KAR subunit mRNA and protein were expressed at levels approximately two and three times higher, respectively, in juvenile mice than in adult mice. A similar expression pattern of the KA1 KAR subunit was observed in an immunohistochemical study that showed higher expression in the juvenile (59%) than those of adult (35%) mice. These results show that the KA1 KAR subunits are expressed in the SG of the Vc in mice and that the expression level of the KA1 KAR subunit decreases gradually with postnatal development. These findings suggest that age-dependent KA1 KAR subunit expression can be a potential mechanism of age-dependent pain perception.
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Affiliation(s)
- Seon Ah Park
- Department of Oral Physiology and BK21 program, Chonbuk National University, Jeonju 561-756, Korea
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Talpalar AE, Kiehn O. Glutamatergic mechanisms for speed control and network operation in the rodent locomotor CpG. Front Neural Circuits 2010; 4. [PMID: 20844601 PMCID: PMC2938926 DOI: 10.3389/fncir.2010.00019] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 07/12/2010] [Indexed: 11/13/2022] Open
Abstract
Locomotion is a fundamental motor act that, to a large degree, is controlled by central pattern-generating (CPG) networks in the spinal cord. Glutamate is thought to be responsible for most of the excitatory input to and the excitatory activity within the locomotor CPG. However, previous studies in mammals have produced conflicting results regarding the necessity and role of the different ionotropic glutamate receptors (GluRs) in the CPG function. Here, we use electrophysiological and pharmacological techniques in the in vitro neonatal mouse lumbar spinal cord to investigate the role of a broad range of ionotropic GluRs in the control of locomotor speed and intrinsic locomotor network function. We show that non-NMDA (non-NMDARs) and NMDA receptor (NMDAR) systems may independently mediate locomotor-like activity and that these receptors set different speeds of locomotor-like activity through mechanisms acting at various network levels. AMPA and kainate receptors are necessary for generating the highest locomotor frequencies. For coordination, NMDARs are more important than non-NMDARs for conveying the rhythmic signal from the network to the motor neurons during long-lasting and steady locomotor activity. This study reveals that a diversity of ionotropic GluRs tunes the network to perform at different locomotor speeds and provides multiple levels for potential regulation and plasticity.
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Affiliation(s)
- Adolfo E Talpalar
- Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet Stockholm, Sweden
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Park SA, Yin H, Bhattarai JP, Park SJ, Lee JC, Kim CJ, Han SK. Postnatal change of GluR5 kainate receptor expression in the substantia gelatinosa neuron of the trigeminal subnucleus caudalis in mice. Brain Res 2010; 1346:52-61. [PMID: 20513362 DOI: 10.1016/j.brainres.2010.05.065] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 05/20/2010] [Accepted: 05/23/2010] [Indexed: 10/19/2022]
Abstract
The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been implicated in the processing of nociceptive information from the orofacial region. Kainate receptors (KARs) play an important role in sensory transmission. Five different KAR subunits have been cloned and the expression of the KAR subunits showed developmental changes. In this study, RT-PCR, western blotting, immunohistochemistry and a patch clamp technique were used examine the functional expression of the GluR5 subunit in the SG of the Vc in juvenile, peripubertal and/or adult mice. The levels of mRNA and protein expression of the GluR5 subunit in the SG of the Vc were higher in the juvenile mice than in the peripubertal or adult mice. In addition, the KA and ATPA, a GluR5 KAR agonist, induced membrane depolarization on the SG neurons in both juvenile and adult mice in a concentration-dependent manner. However, the juvenile SG neurons showed a stronger response to KA and ATPA than those of adults. The membrane depolarization by KA was suppressed slightly in the presence of the AMPA receptor antagonist, GYKI 52466. These results show that the GluR5 KAR subunits are expressed functionally on the SG neurons of the Vc in mice, and the expression levels of the GluR5 subunits decrease with postnatal development. These postnatal changes in the GluR5 KAR subunit may be a possible mechanism for age-dependent pain processing.
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Affiliation(s)
- Seon Ah Park
- Department of Oral Physiology and BK21 program, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju, 561-756, Republic of Korea
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Yogeeswari P, Semwal A, Mishra R, Sriram D. Current approaches with the glutamatergic system as targets in the treatment of neuropathic pain. Expert Opin Ther Targets 2010; 13:925-43. [PMID: 19538098 DOI: 10.1517/14728220903029210] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Glutamate is the most widely distributed and a major excitatory neurotransmitter in the CNS. It has been found to play a critical role in various physiological functions in which increased glutamate or its subsequent stimulation is thought to have a role in pathophysiological mechanism of various CNS diseases like epilepsy, stroke, depression and pain. Early attempts to develop glutamatergic antagonists failed in clinical studies due to nonselective or competitive antagonism and have a lot of safety issues like loss of cognitive functions, psychomimetic effect and sedation. Neuropathic pain can be described as pain associated with damage or permanent alteration of the peripheral or central nervous system. At present, there are very few effective therapies for neuropathic pain. The current approach includes targeting specific or alternate binding sites of glutamate receptors, resulting in reduced CNS liabilities. Targeting the glutamatergic system shows a better efficacy and fewer side effects, compared with classical drugs for the treatment of neuropathic pain. This review discusses the various targets on glutamatergic system, which includes the receptors, transporters and enzymes, for the treatment of neuropathic pain and their advantages over classical glutamatergic antagonists. The review also highlights the newer drugs in clinical trials for neuropathic pain.
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Affiliation(s)
- Perumal Yogeeswari
- BITS-Pilani, Hyderabad Campus, Pharmacy, Shameerpet mandal, Jawahar Nagar, RR District, 500078, Hyderabad, India.
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Larsson M. Ionotropic glutamate receptors in spinal nociceptive processing. Mol Neurobiol 2009; 40:260-88. [PMID: 19876771 DOI: 10.1007/s12035-009-8086-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Accepted: 09/29/2009] [Indexed: 02/07/2023]
Abstract
Glutamate is the predominant excitatory transmitter used by primary afferent synapses and intrinsic neurons in the spinal cord dorsal horn. Accordingly, ionotropic glutamate receptors mediate basal spinal transmission of sensory, including nociceptive, information that is relayed to supraspinal centers. However, it has become gradually more evident that these receptors are also crucially involved in short- and long-term plasticity of spinal nociceptive transmission, and that such plasticity have an important role in the pain hypersensitivity that may result from tissue or nerve injury. This review will cover recent findings on pre- and postsynaptic regulation of synaptic function by ionotropic glutamate receptors in the dorsal horn and how such mechanisms contribute to acute and chronic pain.
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Affiliation(s)
- Max Larsson
- Department of Anatomy and Centre for Molecular Biology and Neuroscience, University of Oslo, Norway.
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Evanson NK, Van Hooren DC, Herman JP. GluR5-mediated glutamate signaling regulates hypothalamo-pituitary-adrenocortical stress responses at the paraventricular nucleus and median eminence. Psychoneuroendocrinology 2009; 34:1370-9. [PMID: 19450932 PMCID: PMC2763572 DOI: 10.1016/j.psyneuen.2009.04.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 03/30/2009] [Accepted: 04/15/2009] [Indexed: 11/26/2022]
Abstract
Glutamate is the main excitatory neurotransmitter in the central nervous system, and plays an excitatory role in generation of hypothalamic-pituitary-adrenocortical (HPA) axis responses to stress. The current study assesses the role of kainate-preferring receptors in glutamatergic excitation of the HPA axis. In situ hybridization and immunohistochemical analyses confirmed the existence of the GluR5 kainate subunit in the paraventricular nucleus of the hypothalamus (PVN). Importantly, GluR5 immunoreactivity was enriched in the external lamina of the median eminence, where it is co-localized with corticotropin releasing hormone (CRH). Intra-PVN infusion of LY382884 increased plasma adrenocorticotropin (ACTH), corticosterone and PVN c-Fos immunoreactivity. Infusions of LY382884 into the median eminence region, on the other hand, reduced restraint induced ACTH release without altering c-Fos expression. Together, these findings provide evidence for glutamate-mediated signaling in control of CRH release at the PVN and median eminence, mediated by way of kainate-preferring receptor complexes.
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Affiliation(s)
- Nathan K. Evanson
- University of Cincinnati Graduate program in Neuroscience,University of Cincinnati Department of Psychiatry,Corresponding author: Nathan K. Evanson, 2170 E. Galbraith Rd, E-205, ML: 0506, Cincinnati, OH 45237, , Tel: (513)558-7629; Fax: (513)558-9104
| | - Daniella C. Van Hooren
- University of Cincinnati Graduate program in Neuroscience,University of Cincinnati Department of Psychiatry
| | - James P. Herman
- University of Cincinnati Graduate program in Neuroscience,University of Cincinnati Department of Psychiatry
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Toyoda H, Zhao MG, Zhuo M. Enhanced quantal release of excitatory transmitter in anterior cingulate cortex of adult mice with chronic pain. Mol Pain 2009; 5:4. [PMID: 19171071 PMCID: PMC2639542 DOI: 10.1186/1744-8069-5-4] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 01/27/2009] [Indexed: 12/02/2022] Open
Abstract
The anterior cingulate cortex (ACC) is a forebrain structure that plays important roles in emotion, learning, memory and persistent pain. Our previous studies have demonstrated that the enhancement of excitatory synaptic transmission was induced by peripheral inflammation and nerve injury in ACC synapses. However, little information is available on their presynaptic mechanisms, since the source of the enhanced synaptic transmission could include the enhanced probability of neurotransmitter release at existing release sites and/or increases in the number of available vesicles. The present study aims to perform quantal analysis of excitatory synapses in the ACC with chronic pain to examine the source of these increases. The quantal analysis revealed that both probability of transmitter release and number of available vesicles were increased in a mouse model of peripheral inflammation, whereas only probability of transmitter release but not number of available vesicles was enhanced in a mouse model of neuropathic pain. In addition, we compared the miniature excitatory postsynaptic potentials (mEPSCs) in ACC synapses with those in other pain-related brain areas such as the amygdala and spinal cord. Interestingly, the rate and amplitude of mEPSCs in ACC synapses were significantly lower than those in the amygdala and spinal cord. Our studies provide strong evidences that chronic inflammatory pain increases both probability of transmitter release and number of available vesicles, whereas neuropathic pain increases only probability of transmitter release in the ACC synapses.
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Affiliation(s)
- Hiroki Toyoda
- Department of Physiology, Faculty of Medicine, Centre for the Study of Pain, University of Toronto, Toronto, Ontario, Canada.
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13
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Kainate receptors: Pharmacology, function and therapeutic potential. Neuropharmacology 2009; 56:90-113. [DOI: 10.1016/j.neuropharm.2008.08.023] [Citation(s) in RCA: 203] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 08/04/2008] [Accepted: 08/07/2008] [Indexed: 01/28/2023]
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Bogulavsky JJ, Gregus AM, Kim PTH, Costa ACS, Rajadhyaksha AM, Inturrisi CE. Deletion of the glutamate receptor 5 subunit of kainate receptors affects the development of morphine tolerance. J Pharmacol Exp Ther 2008; 328:579-87. [PMID: 18957577 DOI: 10.1124/jpet.108.144121] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous reports utilizing pharmacological antagonists implicate kainate receptor (KAR) activation in the development of morphine tolerance, dependence, conditioned place preference (CPP), and locomotor sensitization, but the role of glutamate receptor (GluR) 5-containing KAR in these effects remains unclear because of limited selectivity of the inhibitors employed. Therefore, we examined responses to systemic morphine treatment in mice expressing a constitutive deletion of GluR5 [GluR5 knockout (KO)]. Unlike wild-type (WT) littermates, GluR5 KO mice do not develop tolerance after repeated morphine administration by subcutaneous injection or via subcutaneous pellet implantation. In contrast, GluR5 KO mice do not differ from WT with respect to thermal or mechanical nociceptive thresholds, acute morphine antinociception, morphine disposition in the central nervous system (CNS), morphine physical dependence as revealed by naloxone-precipitated withdrawal or development of place preference and locomotor hyperresponsiveness after chronic morphine administration. It is surprising that continuous subcutaneous infusion of the GluR2/GluR5-preferring antagonist LY293558 [(3S,4aR,6R,8aR)-6-[2-(1(2)H-tetrazole-5-yl)ethyl]decahydroisoquinoline-3-carboxylic acid] decreased the number of naloxone-precipitated jumps to a similar extent in WT and GluR5 KO mice. We observed opioid-induced hypersensitivity in both groups during morphine withdrawal as demonstrated by equivalent reductions in thermal and mechanical thresholds; however, this hypersensitivity was not evident during continuous systemic morphine infusion. These data collectively indicate that KARs containing the GluR5 subunit contribute to the development of morphine tolerance without affecting nociceptive thresholds, morphine analgesia, or disposition in CNS of morphine and its metabolite morphine-3-glucuronide. In addition, constitutive deletion of GluR5 does not alter the morphine-induced increase in locomotor activity or the acquisition of morphine reward as measured by a CPP paradigm.
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Affiliation(s)
- Johanna J Bogulavsky
- Department of Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA
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Mathew SS, Hablitz JJ. Calcium release via activation of presynaptic IP3 receptors contributes to kainate-induced IPSC facilitation in rat neocortex. Neuropharmacology 2008; 55:106-16. [PMID: 18508095 DOI: 10.1016/j.neuropharm.2008.05.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 04/14/2008] [Accepted: 05/05/2008] [Indexed: 10/22/2022]
Abstract
We examined the mechanisms of kainate (KA) induced modulation of GABA release in rat prefrontal cortex. Pharmacologically isolated IPSCs were recorded from visually identified layer II/III pyramidal cells using whole-cell patch clamp techniques. KA produced an increase in evoked IPSC amplitude at low nanomolar concentrations (100-500 nM). The frequency but not the amplitude of miniature (m) IPSCs was also increased. The GluR5 subunit selective agonist (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA) caused an increase in mIPSC frequency whereas (3S,4aR,6S,8aR)-6-(4-carboxyphenyl)methyl-1,2,3,4,4a,5,6,7,8,8a-decahydroisoquinoline-3-carboxylic acid (LY382884), a selective GluR5 subunit antagonist, inhibited this facilitation. Philanthotoxin-433 (PhTx) blocked the effect of KA, indicating involvement of Ca(2+)-permeable GluR5 receptors. No IPSC facilitation was seen when Ca(2+) was omitted from the bathing solution. Facilitation was observed when slices were preincubated in ruthenium red or high concentrations of ryanodine, but was inhibited with application of thapsigargin. The IP3 receptor (IP3R) antagonists diphenylboric acid 2-amino-ethyl ester (2-APB) (15 microM) and Xestospongin C (XeC) blocked IPSC facilitation. These results show that activation of KA receptors (KARs) on GABAergic nerve terminals results is linked to intracellular Ca(2+) release via activation of IP3, but not ryanodine, receptors. This represents a new mechanism of presynaptic modulation whereby Ca(2+) entry through Ca(2+)-permeable GluR5 subunit containing KARs activates IP3Rs receptors leading to an increase in GABA release.
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Affiliation(s)
- Seena S Mathew
- Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Wu LJ, Ko SW, Toyoda H, Zhao MG, Xu H, Vadakkan KI, Ren M, Knifed E, Shum F, Quan J, Zhang XH, Zhuo M. Increased anxiety-like behavior and enhanced synaptic efficacy in the amygdala of GluR5 knockout mice. PLoS One 2007; 2:e167. [PMID: 17245443 PMCID: PMC1766473 DOI: 10.1371/journal.pone.0000167] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Accepted: 12/28/2006] [Indexed: 11/19/2022] Open
Abstract
GABAergic transmission in the amygdala modulates the expression of anxiety. Understanding the interplay between GABAergic transmission and excitatory circuits in the amygdala is, therefore, critical for understanding the neurobiological basis of anxiety. Here, we used a multi-disciplinary approach to demonstrate that GluR5-containing kainate receptors regulate local inhibitory circuits, modulate the excitatory transmission from the basolateral amygdala to the central amygdala, and control behavioral anxiety. Genetic deletion of GluR5 or local injection of a GluR5 antagonist into the basolateral amygdala increases anxiety-like behavior. Activation of GluR5 selectively depolarized inhibitory neurons, thereby increasing GABA release and contributing to tonic GABA current in the basolateral amygdala. The enhanced GABAergic transmission leads to reduced excitatory inputs in the central amygdala. Our results suggest that GluR5 is a key regulator of inhibitory circuits in the amygdala and highlight the potential use of GluR5-specific drugs in the treatment of pathological anxiety.
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Affiliation(s)
- Long-Jun Wu
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Shanelle W. Ko
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Hiroki Toyoda
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Ming-Gao Zhao
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Hui Xu
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Kunjumon I. Vadakkan
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Ming Ren
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Eva Knifed
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Fanny Shum
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Jessica Quan
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Xue-Han Zhang
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Min Zhuo
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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