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Imbriotis V, Ranson A, Connelly WM. RPG: A low-cost, open-source, high-performance solution for displaying visual stimuli. J Neurosci Methods 2021; 363:109343. [PMID: 34464650 DOI: 10.1016/j.jneumeth.2021.109343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 08/24/2021] [Accepted: 08/26/2021] [Indexed: 10/20/2022]
Abstract
BACKGROUND The development of new high throughput approaches for neuroscience such as high-density silicon probes and 2-photon imaging have led to a renaissance in visual neuroscience. However, generating the stimuli needed to evoke activity in the visual system still represents a non-negligible difficulty for experimentalists. While several widely used software toolkits exist to deliver such stimuli, they all suffer from some shortcomings. Primarily, the hardware needed to effectively display such stimuli comes at a significant financial cost, and secondly, triggering and/or timing the stimuli such that it can be accurately synchronized with other devices requires the use of legacy hardware, further hardware, or bespoke solutions. RESULTS Here we present RPG (Raspberry Pi Gratings), a Python package written for the Raspberry Pi, which overcomes these issues. Specifically, the Raspberry Pi is a low-cost, credit card sized computer with general purpose input/output pins, allowing RPG to be triggered to deliver stimuli and to provide real-time feedback on stimulus timing. RPG delivers stimuli at 60 frames per second and the feedback of frame timings is accurate to 10s of microseconds. COMPARISON WITH EXISTING METHOD(S) With respect to the accuracy of frame timings, the performance of RPG is at least as accurate as commonly used packages. However, the inbuilt ability to trigger stimuli and the real-time feedback of frame timings will be extremely useful for certain experiments. CONCLUSIONS RPG provides a simple to use Python interface that is capable of generating drifting sine wave gratings, Gabor patches and displaying raw images/video.
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Affiliation(s)
- Vivian Imbriotis
- School of Medicine, University of Tasmania, Hobart, Australia; Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain; Institut de Neurociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Adam Ranson
- Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain; Institut de Neurociènces, Universitat Autònoma de Barcelona, Bellaterra, Spain.
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Powell A, Connelly WM, Vasalauskaite A, Nelson AJD, Vann SD, Aggleton JP, Sengpiel F, Ranson A. Stable Encoding of Visual Cues in the Mouse Retrosplenial Cortex. Cereb Cortex 2020; 30:4424-4437. [PMID: 32147692 PMCID: PMC7438634 DOI: 10.1093/cercor/bhaa030] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The rodent retrosplenial cortex (RSC) functions as an integrative hub for sensory and motor signals, serving roles in both navigation and memory. While RSC is reciprocally connected with the sensory cortex, the form in which sensory information is represented in the RSC and how it interacts with motor feedback is unclear and likely to be critical to computations involved in navigation such as path integration. Here, we used 2-photon cellular imaging of neural activity of putative excitatory (CaMKII expressing) and inhibitory (parvalbumin expressing) neurons to measure visual and locomotion evoked activity in RSC and compare it to primary visual cortex (V1). We observed stimulus position and orientation tuning, and a retinotopic organization. Locomotion modulation of activity of single neurons, both in darkness and light, was more pronounced in RSC than V1, and while locomotion modulation was strongest in RSC parvalbumin-positive neurons, visual-locomotion integration was found to be more supralinear in CaMKII neurons. Longitudinal measurements showed that response properties were stably maintained over many weeks. These data provide evidence for stable representations of visual cues in RSC that are spatially selective. These may provide sensory data to contribute to the formation of memories of spatial information.
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Affiliation(s)
- Anna Powell
- School of Psychology, Cardiff University, CF10 3AS Cardiff, UK
| | | | | | | | | | - John P Aggleton
- School of Psychology, Cardiff University, CF10 3AS Cardiff, UK
| | - Frank Sengpiel
- School of Biosciences, Cardiff University, Cardiff, CF10 3AX, UK.,Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK
| | - Adam Ranson
- Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, CF24 4HQ, UK.,Faculty of Medicine and Health Sciences, Department of Basic Sciences, Universitat Internacional de Catalunya, Barcelona, 08195, Spain.,Institut de Neurociènces, Universitat Autònoma de Barcelona, Bellaterra, 08193, Spain
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Abstract
While many studies indicate that dendrites can perform a range of local computations on their inputs, work from the Harnett lab in this issue of Neuron suggests that the vast majority of active dendritic events are synchronized across the somato-dendritic axis of cortical pyramidal neurons.
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Affiliation(s)
| | - Greg J Stuart
- Eccles Institute of Neuroscience and Australian Research Council Centre of Excellence for Integrative Brain Function, John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia.
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Trent S, Hall J, Connelly WM, Errington AC. Cyfip1 Haploinsufficiency Does Not Alter GABA A Receptor δ-Subunit Expression and Tonic Inhibition in Dentate Gyrus PV + Interneurons and Granule Cells. eNeuro 2019; 6:ENEURO.0364-18.2019. [PMID: 31209152 PMCID: PMC6635810 DOI: 10.1523/eneuro.0364-18.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 05/28/2019] [Accepted: 05/31/2019] [Indexed: 12/01/2022] Open
Abstract
Copy number variation (CNV) at chromosomal region 15q11.2 is linked to increased risk of neurodevelopmental disorders including autism and schizophrenia. A significant gene at this locus is cytoplasmic fragile X mental retardation protein (FMRP) interacting protein 1 (CYFIP1). CYFIP1 protein interacts with FMRP, whose monogenic absence causes fragile X syndrome (FXS). Fmrp knock-out has been shown to reduce tonic GABAergic inhibition by interacting with the δ-subunit of the GABAA receptor (GABAAR). Using in situ hybridization (ISH), qPCR, Western blotting techniques, and patch clamp electrophysiology in brain slices from a Cyfip1 haploinsufficient mouse, we examined δ-subunit mediated tonic inhibition in the dentate gyrus (DG). In wild-type (WT) mice, DG granule cells (DGGCs) responded to the δ-subunit-selective agonist THIP with significantly increased tonic currents. In heterozygous mice, no significant difference was observed in THIP-evoked currents in DGGCs. Phasic GABAergic inhibition in DGGC was also unaltered with no difference in properties of spontaneous IPSCs (sIPSCs). Additionally, we demonstrate that DG granule cell layer (GCL) parvalbumin-positive interneurons (PV+-INs) have functional δ-subunit-mediated tonic GABAergic currents which, unlike DGGC, are also modulated by the α1-selective drug zolpidem. Similar to DGGC, both IPSCs and THIP-evoked currents in PV+-INs were not different between Cyfip1 heterozygous and WT mice. Supporting our electrophysiological data, we found no significant change in hippocampal δ-subunit mRNA expression or protein level and no change in α1/α4-subunit mRNA expression. Thus, Cyfip1 haploinsufficiency, mimicking human 15q11.2 microdeletion syndrome, does not alter hippocampal phasic or tonic GABAergic inhibition, substantially differing from the Fmrp knock-out mouse model.
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Affiliation(s)
- Simon Trent
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
| | - Jeremy Hall
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
| | - William M Connelly
- School of Medicine, University of Tasmania, Hobart, Tasmania 7000, Australia
| | - Adam C Errington
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, CF24 4HQ, United Kingdom
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McCafferty C, Connelly WM, Celli R, Ngomba RT, Nicoletti F, Crunelli V. Genetic rescue of absence seizures. CNS Neurosci Ther 2018; 24:745-758. [PMID: 29687641 PMCID: PMC6055804 DOI: 10.1111/cns.12858] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 03/11/2018] [Accepted: 03/13/2018] [Indexed: 11/26/2022] Open
Affiliation(s)
- Cian McCafferty
- Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK
| | - William M Connelly
- Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK
| | | | | | | | - Vincenzo Crunelli
- Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK.,Department of Physiology and Biochemistry, University of Malta, Msida, Malta
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Crunelli V, Lőrincz ML, Connelly WM, David F, Hughes SW, Lambert RC, Leresche N, Errington AC. Dual function of thalamic low-vigilance state oscillations: rhythm-regulation and plasticity. Nat Rev Neurosci 2018; 19:107-118. [PMID: 29321683 DOI: 10.1038/nrn.2017.151] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
During inattentive wakefulness and non-rapid eye movement (NREM) sleep, the neocortex and thalamus cooperatively engage in rhythmic activities that are exquisitely reflected in the electroencephalogram as distinctive rhythms spanning a range of frequencies from <1 Hz slow waves to 13 Hz alpha waves. In the thalamus, these diverse activities emerge through the interaction of cell-intrinsic mechanisms and local and long-range synaptic inputs. One crucial feature, however, unifies thalamic oscillations of different frequencies: repetitive burst firing driven by voltage-dependent Ca2+ spikes. Recent evidence reveals that thalamic Ca2+ spikes are inextricably linked to global somatodendritic Ca2+ transients and are essential for several forms of thalamic plasticity. Thus, we propose herein that alongside their rhythm-regulation function, thalamic oscillations of low-vigilance states have a plasticity function that, through modifications of synaptic strength and cellular excitability in local neuronal assemblies, can shape ongoing oscillations during inattention and NREM sleep and may potentially reconfigure thalamic networks for faithful information processing during attentive wakefulness.
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Affiliation(s)
- Vincenzo Crunelli
- Department of Physiology and Biochemistry, University of Malta, Msida, Malta; and the Neuroscience Division, School of Bioscience, Cardiff University, Cardiff, UK
| | - Magor L Lőrincz
- Research Group for Cellular and Network Neurophysiology of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Szeged, Hungary
| | - William M Connelly
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australia
| | - François David
- Lyon Neuroscience Research Center, Centre national de la recherche scientifique (CNRS) unité mixte de recherche (UMR) 5292- INSERM U1028-Université Claude Bernard, Lyon, France
| | | | - Régis C Lambert
- Sorbonne Universités, University Pierre and Marie Curie (UPMC) Univ. Paris 06, INSERM, Centre national de la recherche scientifique (CNRS), Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris, France
| | - Nathalie Leresche
- Sorbonne Universités, University Pierre and Marie Curie (UPMC) Univ. Paris 06, INSERM, Centre national de la recherche scientifique (CNRS), Neurosciences Paris Seine - Institut de Biologie Paris Seine (NPS - IBPS), Paris, France
| | - Adam C Errington
- Neuroscience and Mental Health Research Institute, School of Medicine, Cardiff University, Cardiff, UK
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Connelly WM, Laing M, Errington AC, Crunelli V. The Thalamus as a Low Pass Filter: Filtering at the Cellular Level does Not Equate with Filtering at the Network Level. Front Neural Circuits 2016; 9:89. [PMID: 26834570 PMCID: PMC4712306 DOI: 10.3389/fncir.2015.00089] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/22/2015] [Indexed: 11/20/2022] Open
Abstract
In the mammalian central nervous system, most sensory information passes through primary sensory thalamic nuclei, however the consequence of this remains unclear. Various propositions exist, likening the thalamus to a gate, or a high pass filter. Here, using a simple leaky integrate and fire model based on physiological parameters, we show that the thalamus behaves akin to a low pass filter. Specifically, as individual cells in the thalamus rely on consistent drive to spike, stimuli that is rapidly and continuously changing over time such that it activates sensory cells with different receptive fields are unable to drive thalamic spiking. This means that thalamic encoding is robust to sensory noise, however it induces a lag in sensory representation. Thus, the thalamus stabilizes encoding of sensory information, at the cost of response rate.
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Affiliation(s)
- William M Connelly
- Division of Neuroscience, School of Biosciences, Cardiff UniversityCardiff, UK; Eccles Institute of Neuroscience, The John Curtin School of Medical Research, The Australian National UniversityCanberra, ACT, Australia
| | - Michael Laing
- School of Medicine, Neuroscience and Mental Health Research Institute, Cardiff University Cardiff, UK
| | - Adam C Errington
- School of Medicine, Neuroscience and Mental Health Research Institute, Cardiff University Cardiff, UK
| | - Vincenzo Crunelli
- Division of Neuroscience, School of Biosciences, Cardiff UniversityCardiff, UK; Department of Physiology and Biochemistry, University of MaltaMsida, Malta
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Abstract
Thalamocortical neurons integrate sensory and cortical activity and are regulated by input from inhibitory neurons in the thalamic reticular nucleus. Evidence suggests that during bursts of action potentials, dendritic calcium transients are seen throughout the dendritic tree of thalamocortical cells. Here, we review a recent study that suggests these calcium transients regulate inhibitory input, and we attempt to reconcile studies that differ on which ion channels are the source of the calcium.
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Affiliation(s)
- Sarah R Hulme
- School of Physiology and Pharmacology, School of Medical Sciences, Bristol, United Kingdom; and
| | - William M Connelly
- Neuroscience Division, Cardiff School of Biosciences, Cardiff, United Kingdom
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Abstract
Computational models of gamma oscillations have helped increase our understanding of the mechanisms that shape these 40–80 Hz cortical rhythms. Evidence suggests that interneurons known as basket cells are responsible for the generation of gamma oscillations. However, current models of gamma oscillations lack the dynamic short term synaptic plasticity seen at basket cell-basket cell synapses as well as the large autaptic synapses basket cells are known to express. Hence, I sought to extend the Wang-Buzsáki model of gamma oscillations to include these features. I found that autapses increased the synchrony of basket cell membrane potentials across the network during neocortical gamma oscillations as well as allowed the network to oscillate over a broader range of depolarizing drive. I also found that including realistic synaptic depression filtered the output of the network. Depression restricted the network to oscillate in the 60–80 Hz range rather than the 40–120 Hz range seen in the standard model. This work shows the importance of including accurate synapses in any future model of gamma oscillations.
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Affiliation(s)
- William M Connelly
- Neuroscience Division, School of Biosciences, Cardiff University, Life Sciences Building, Cardiff, United Kingdom
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10
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Abstract
γ-Hydroxybutyric acid (GHB) is an endogenous compound and a drug used clinically to treat the symptoms of narcolepsy. GHB is known to be an agonist of GABAB receptors with millimolar affinity, but also binds with much higher affinity to another site, known as the GHB receptor. While a body of evidence has shown that GHB does not bind to GABAA receptors widely, recent evidence has suggested that the GHB receptor is in fact on extrasynaptic α4β1δ GABAA receptors, where GHB acts as an agonist with an EC50 of 140 nM. We investigated three neuronal cell types that express a tonic GABAA receptor current mediated by extrasynaptic receptors: ventrobasal (VB) thalamic neurons, dentate gyrus granule cells and striatal medium spiny neurons. Using whole-cell voltage clamp in brain slices, we found no evidence that GHB (10 µM) induced any GABAA receptor mediated current in these cell types, nor that it modulated inhibitory synaptic currents. Furthermore, a high concentration of GHB (3 mM) was able to produce a GABAB receptor mediated current, but did not induce any other currents. These results suggest either that GHB is not a high affinity agonist at native α4β1δ receptors, or that these receptors do not exist in classical areas associated with extrasynaptic currents.
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Affiliation(s)
- William M. Connelly
- Neuroscience Division, Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom
- * E-mail: (WMC); (VC)
| | - Adam C. Errington
- Neuroscience Division, Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom
| | - Vincenzo Crunelli
- Neuroscience Division, Cardiff School of Biosciences, Cardiff University, Cardiff, United Kingdom
- * E-mail: (WMC); (VC)
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11
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Connelly WM, Errington AC, Di Giovanni G, Crunelli V. Metabotropic regulation of extrasynaptic GABAA receptors. Front Neural Circuits 2013; 7:171. [PMID: 24298239 PMCID: PMC3829460 DOI: 10.3389/fncir.2013.00171] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 10/03/2013] [Indexed: 01/28/2023] Open
Abstract
A large body of work now shows the importance of GABAA receptor-mediated tonic inhibition in regulating CNS function. However, outside of pathological conditions, there is relatively little evidence that the magnitude of tonic inhibition is itself under regulation. Here we review the mechanisms by which tonic inhibition is known to be modulated, and outline the potential behavioral consequences of this modulation. Specifically, we address the ability of protein kinase A and C to phosphorylate the extrasynaptic receptors responsible for the tonic GABAA current, and how G-protein coupled receptors can regulate tonic inhibition through these effectors. We then speculate about the possible functional consequences of regulating the magnitude of the tonic GABAA current.
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Affiliation(s)
- William M Connelly
- Neuroscience Division, Cardiff School of Biosciences, Cardiff University Cardiff, UK
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12
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Abstract
Neocortical fast-spiking (FS) basket cells form dense autaptic connections that provide inhibitory GABAergic feedback after each action potential. It has been suggested that these autaptic connections are used because synaptic communication is sensitive to neuromodulation, unlike the voltage-sensitive potassium channels in FS cells. Here we show that layer V FS interneurons form autaptic connections that are largely perisomatic, and without perturbing intracellular Cl(-) homeostasis, that perisomatic GABAergic currents have a reversal potential of 78 +/- 4 mV. Using variance-mean analysis, we demonstrate that autaptic connections have a mean of 14 release sites (range 4-26) with a quantal amplitude of 101 +/- 16 pA and a probability of release of 0.64 (V(command) = 70 mV, [Ca(2+)](o) = 2 mM, [Mg(2+)](o) = 1 mM). We found that autaptic GABA release is sensitive to GABA(B) and muscarinic acetylcholine receptors, but not a range of other classical neuromodulators. Our results indicate that GABA transporters do not regulate FS interneuron autapses, yet autaptically released GABA does not act at GABA(B) or extrasynaptic GABA(A) receptors. This research confirms that the autaptic connections of FS cells are indeed susceptible to modulation, though only via specific GABAergic and cholinergic mechanisms.
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Affiliation(s)
- William M Connelly
- Department of Pharmacology and Toxicology, School of Medical Sciences, University of Otago, Dunedin, New Zealand
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Connelly WM, Shenton FC, Lethbridge N, Leurs R, Waldvogel HJ, Faull RLM, Lees G, Chazot PL. The histamine H4 receptor is functionally expressed on neurons in the mammalian CNS. Br J Pharmacol 2009; 157:55-63. [PMID: 19413571 DOI: 10.1111/j.1476-5381.2009.00227.x] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE The histamine H4 receptor is the most recently identified of the G protein-coupled histamine receptor family and binds several neuroactive drugs, including amitriptyline and clozapine. So far, H4 receptors have been found only on haematopoietic cells, highlighting its importance in inflammatory conditions. Here we investigated the possibility that H4 receptors may be expressed in both the human and mouse CNS. METHODS Immunological and pharmacological studies were performed using a novel anti-H4 receptor antibody in both human and mouse brains, and electrophysiological techniques in the mouse brain respectively. Pharmacological tools, selective for the H4 receptor and patch clamp electrophysiology, were utilized to confirm functional properties of the H4 receptor in layer IV of the mouse somatosensory cortex. RESULTS Histamine H4 receptors were prominently expressed in distinct deep laminae, particularly layer VI, in the human cortex, and mouse thalamus, hippocampal CA4 stratum lucidum and layer IV of the cerebral cortex. In layer IV of the mouse somatosensory cortex, the H4 receptor agonist 4-methyl histamine (20 micromol x L(-1)) directly hyperpolarized neurons, an effect that was blocked by the selective H4 receptor antagonist JNJ 10191584, and promoted outwardly rectifying currents in these cells. Monosynaptic thalamocortical CNQX-sensitive excitatory postsynaptic potentials were not altered by 4-methyl histamine (20 micromol x L(-1)) suggesting that H4 receptors did not act as hetero-receptors on thalamocortical glutamatergic terminals. CONCLUSIONS AND IMPLICATIONS This is the first demonstration that histamine H4 receptors are functionally expressed on neurons, which has major implications for the therapeutic potential of these receptors in neurology and psychiatry.
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Affiliation(s)
- W M Connelly
- Department of Pharmacology & Toxicology, School of Medical Sciences, University of Otago, Dunedin, New Zealand
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Abstract
Endocannabinoids are lipid retrograde messengers that can be released by postsynaptic depolarization and/or activation of certain metabotropic receptors. We review a recent report that activation of metabotropic 5-HT2 receptors by endogenous serotonin induces the release of endocannabinoids in the olivary nucleus and suppresses glutamatergic input through a presynaptic action. This serotonin-endocannabinoid interaction has implications in the pathophysiology of pain and mental illness and raises the possibility that drugs targeting the 5-HT2 receptor may act by modulating endocannabinoid release.
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Affiliation(s)
- William M Connelly
- Department of Pharmacology and Toxicology, Otago School of Medical Sciences, University of Otago, P.O. Box 913, Dunedin, New Zealand.
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Payne HL, Connelly WM, Ives JH, Lehner R, Furtmuller B, Sieghart W, Tiwari P, Lucocq JM, Lees G, Thompson CL. GABAA alpha6-containing receptors are selectively compromised in cerebellar granule cells of the ataxic mouse, stargazer. J Biol Chem 2007; 282:29130-43. [PMID: 17646167 PMCID: PMC2974090 DOI: 10.1074/jbc.m700111200] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Stargazer mice fail to express the gamma2 isoform of transmembrane alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) receptor regulatory proteins that has been shown to be absolutely required for the trafficking and synaptic targeting of excitatory AMPA receptors in adult murine cerebellar granule cells. Here we show that 30 +/- 6% fewer inhibitory gamma-aminobutyric acid, type A (GABA(A)), receptors were expressed in adult stargazer cerebellum compared with controls because of a specific loss of GABA(A) receptor expression in the cerebellar granule cell layer. Radioligand binding assays allied to in situ immunogold-EM analysis and furosemide-sensitive tonic current estimates revealed that expression of the extrasynaptic (alpha6betaxdelta) alpha6-containing GABA(A) receptor were markedly and selectively reduced in stargazer. These observations were compatible with a marked reduction in expression of GABA(A) receptor alpha6, delta (mature cerebellar granule cell-specific proteins), and beta3 subunit expression in stargazer. The subunit composition of the residual alpha6-containing GABA(A) receptors was unaffected by the stargazer mutation. However, we did find evidence of an approximately 4-fold up-regulation of alpha1betadelta receptors that may compensate for the loss of alpha6-containing GABA(A) receptors. PCR analysis identified a dramatic reduction in the steady-state level of alpha6 mRNA, compatible with alpha6 being the primary target of the stargazer mutation-mediated GABA(A) receptor abnormalities. We propose that some aspects of assembly, trafficking, targeting, and/or expression of extrasynaptic alpha6-containing GABA(A) receptors in cerebellar granule cells are selectively regulated by AMPA receptor-mediated signaling.
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Affiliation(s)
- Helen L Payne
- Centre for Integrative Neurosciences, School of Biological and Biomedical Sciences, Science Research Laboratories, Durham University, South Road, Durham DH1 3LE, United Kingdom.
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