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Athiraman U, Giri T. Isoflurane preconditioning induced genomic changes in mouse cortex. BJA Open 2024; 10:100268. [PMID: 38545566 PMCID: PMC10966196 DOI: 10.1016/j.bjao.2024.100268] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 02/26/2024] [Indexed: 05/16/2024]
Abstract
Background Altered patterns of genetic expression induced by isoflurane preconditioning in mouse brain have not yet been investigated. The aim of our pilot study is to examine the temporal sequence of changes in the transcriptome of mouse brain cortex produced by isoflurane preconditioning. Methods Twelve-wk-old wild-type (C57BL/6J) male mice were randomly assigned for the experiments. Mice were exposed to isoflurane 2% in air for 1 h and brains were harvested at the following time points-immediately (0 h), and at 6, 12, 24, 36, 48, and 72 h after isoflurane exposure. A separate cohort of mice were exposed to three doses of isoflurane on days 1, 2, and 3 and brains were harvested after the third exposure. The NanoString mouse neuropathology panel was used to analyse isoflurane-induced gene expression in the cortex. The neuropathology panel included 760 genes covering pathways involved in neurodegeneration and other nervous system diseases, and 10 internal reference genes for data normalisation. Results Genes involving several pathways were upregulated and downregulated by isoflurane preconditioning. Interestingly, a biphasic response was noted, meaning, an early expression of genes (until 6 h), followed by a transient pause (until 24 h), and a second wave of genomic response beginning at 36 h of isoflurane exposure was noted. Conclusions Isoflurane preconditioning induces significant alterations in the genes involved in neurodegeneration and other nervous system disorders in a temporal sequence. These data could aid in the identification of molecular mechanisms behind isoflurane preconditioning-induced neuroprotection in various central nervous system diseases.
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Affiliation(s)
- Umeshkumar Athiraman
- Department of Anesthesiology, Washington University, St. Louis, MO, USA
- Department of Neurological Surgery, Washington University, St. Louis, MO, USA
| | - Tusar Giri
- Department of Anesthesiology, Washington University, St. Louis, MO, USA
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Espinosa-Medina I, Feliciano D, Belmonte-Mateos C, Linda Miyares R, Garcia-Marques J, Foster B, Lindo S, Pujades C, Koyama M, Lee T. TEMPO enables sequential genetic labeling and manipulation of vertebrate cell lineages. Neuron 2023; 111:345-361.e10. [PMID: 36417906 DOI: 10.1016/j.neuron.2022.10.035] [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] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 08/15/2022] [Accepted: 10/26/2022] [Indexed: 11/24/2022]
Abstract
During development, regulatory factors appear in a precise order to determine cell fates over time. Consequently, to investigate complex tissue development, it is necessary to visualize and manipulate cell lineages with temporal control. Current strategies for tracing vertebrate cell lineages lack genetic access to sequentially produced cells. Here, we present TEMPO (Temporal Encoding and Manipulation in a Predefined Order), an imaging-readable genetic tool allowing differential labeling and manipulation of consecutive cell generations in vertebrates. TEMPO is based on CRISPR and powered by a cascade of gRNAs that drive orderly activation and inactivation of reporters and/or effectors. Using TEMPO to visualize zebrafish and mouse neurogenesis, we recapitulated birth-order-dependent neuronal fates. Temporally manipulating cell-cycle regulators in mouse cortex progenitors altered the proportion and distribution of neurons and glia, revealing the effects of temporal gene perturbation on serial cell fates. Thus, TEMPO enables sequential manipulation of molecular factors, crucial to study cell-type specification.
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Affiliation(s)
| | - Daniel Feliciano
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Carla Belmonte-Mateos
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona 08003, Spain
| | - Rosa Linda Miyares
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Jorge Garcia-Marques
- Centro Nacional de Biotecnologia, Consejo Superior de Investigaciones Cientificas, Madrid 28049, Spain
| | - Benjamin Foster
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Sarah Lindo
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Cristina Pujades
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, PRBB, Barcelona 08003, Spain
| | - Minoru Koyama
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA; Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Tzumin Lee
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA.
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Rasmussen M, Welinder C, Schwede F, Ekström P. The stereospecific interaction sites and target specificity of cGMP analogs in mouse cortex. Chem Biol Drug Des 2021; 99:206-221. [PMID: 34687134 DOI: 10.1111/cbdd.13976] [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: 08/01/2021] [Revised: 09/29/2021] [Accepted: 10/16/2021] [Indexed: 11/30/2022]
Abstract
cGMP interactors play a role in several pathologies and may be targets for cGMP analog-based drugs, but the success of targeting depends on the biochemical stereospecificity between the cGMP-analog and the interactor. The stereospecificity between general cGMP analogs-or such that are selectivity-modified to obtain, for example, inhibitory actions on a specific target, like the cGMP-dependent protein kinase-have previously been investigated. However, the importance of stereospecificity for cGMP-analog binding to interactors is not known. We, therefore, applied affinity chromatography on mouse cortex proteins utilizing analogs with cyclic phosphate (8-AET-cGMP, 2-AH-cGMP, 2'-AHC-cGMP) and selectivity-modified analogs with sulfur-containing cyclic phosphorothioates (Rp/Sp-8-AET-cGMPS, Rp/Sp-2'-AHC-cGMPS) immobilized to agaroses. The results illustrate the cGMP analogs' stereospecific binding for PKG, PKA regulatory subunits and PKA catalytic subunits, PDEs, and EPAC2 and the involvement of these in various KEGG pathways. For the seven agaroses, PKG, PKA regulatory subunits, and PKA catalytic subunits were more prone to be enriched by 2-AH-, 8-AET-, Rp-8-AET-, and Sp-8-AET-cGMP, whereas PDEs and EPAC2 were more likely to be enriched by 2-AH-, Rp-2'-AHC-, and Rp-8-AET-cGMP. Our findings help elucidate the stereospecific-binding sites essential for the interaction between individual cGMP analogs and cGMP-binding proteins, as well as the cGMP analogs' target specificity, which are two crucial parameters in drug design.
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Affiliation(s)
- Michel Rasmussen
- Faculty of Medicine, Department of Clinical Sciences Lund, Ophthalmology, Lund University, Lund, Sweden
| | - Charlotte Welinder
- Faculty of Medicine, Department of Clinical Sciences Lund, Oncology, Lund University, Lund, Sweden
| | - Frank Schwede
- BIOLOG Life Science Institute GmbH & Co. KG, Bremen, Germany
| | - Per Ekström
- Faculty of Medicine, Department of Clinical Sciences Lund, Ophthalmology, Lund University, Lund, Sweden
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Forli A, Pisoni M, Printz Y, Yizhar O, Fellin T. Optogenetic strategies for high-efficiency all-optical interrogation using blue-light-sensitive opsins. eLife 2021; 10:63359. [PMID: 34032211 PMCID: PMC8177884 DOI: 10.7554/elife.63359] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [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: 09/22/2020] [Accepted: 05/24/2021] [Indexed: 12/20/2022] Open
Abstract
All-optical methods for imaging and manipulating brain networks with high spatial resolution are fundamental to study how neuronal ensembles drive behavior. Stimulation of neuronal ensembles using two-photon holographic techniques requires high-sensitivity actuators to avoid photodamage and heating. Moreover, two-photon-excitable opsins should be insensitive to light at wavelengths used for imaging. To achieve this goal, we developed a novel soma-targeted variant of the large-conductance blue-light-sensitive opsin CoChR (stCoChR). In the mouse cortex in vivo, we combined holographic two-photon stimulation of stCoChR with an amplified laser tuned at the opsin absorption peak and two-photon imaging of the red-shifted indicator jRCaMP1a. Compared to previously characterized blue-light-sensitive soma-targeted opsins in vivo, stCoChR allowed neuronal stimulation with more than 10-fold lower average power and no spectral crosstalk. The combination of stCoChR, tuned amplified laser stimulation, and red-shifted functional indicators promises to be a powerful tool for large-scale interrogation of neural networks in the intact brain.
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Affiliation(s)
- Angelo Forli
- Optical Approaches to Brain Function Laboratory, Istituto Italiano di Tecnologia, Genova, Italy
| | - Matteo Pisoni
- Optical Approaches to Brain Function Laboratory, Istituto Italiano di Tecnologia, Genova, Italy.,Università di Genova, Genova, Italy
| | - Yoav Printz
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
| | - Ofer Yizhar
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
| | - Tommaso Fellin
- Optical Approaches to Brain Function Laboratory, Istituto Italiano di Tecnologia, Genova, Italy
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Moudgil A, Wilkinson MN, Chen X, He J, Cammack AJ, Vasek MJ, Lagunas T, Qi Z, Lalli MA, Guo C, Morris SA, Dougherty JD, Mitra RD. Self-Reporting Transposons Enable Simultaneous Readout of Gene Expression and Transcription Factor Binding in Single Cells. Cell 2020; 182:992-1008.e21. [PMID: 32710817 PMCID: PMC7510185 DOI: 10.1016/j.cell.2020.06.037] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 04/14/2020] [Accepted: 06/23/2020] [Indexed: 12/13/2022]
Abstract
Cellular heterogeneity confounds in situ assays of transcription factor (TF) binding. Single-cell RNA sequencing (scRNA-seq) deconvolves cell types from gene expression, but no technology links cell identity to TF binding sites (TFBS) in those cell types. We present self-reporting transposons (SRTs) and use them in single-cell calling cards (scCC), a novel assay for simultaneously measuring gene expression and mapping TFBS in single cells. The genomic locations of SRTs are recovered from mRNA, and SRTs deposited by exogenous, TF-transposase fusions can be used to map TFBS. We then present scCC, which map SRTs from scRNA-seq libraries, simultaneously identifying cell types and TFBS in those same cells. We benchmark multiple TFs with this technique. Next, we use scCC to discover BRD4-mediated cell-state transitions in K562 cells. Finally, we map BRD4 binding sites in the mouse cortex at single-cell resolution, establishing a new method for studying TF biology in situ.
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Affiliation(s)
- Arnav Moudgil
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Medical Scientist Training Program, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Michael N Wilkinson
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Xuhua Chen
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - June He
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Alexander J Cammack
- Department of Neurology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Michael J Vasek
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Tomás Lagunas
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Zongtai Qi
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Matthew A Lalli
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Chuner Guo
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Medical Scientist Training Program, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Samantha A Morris
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Center of Regenerative Medicine, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Joseph D Dougherty
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Robi D Mitra
- Department of Genetics, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA; Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA.
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Wang Q, Ding SL, Li Y, Royall J, Feng D, Lesnar P, Graddis N, Naeemi M, Facer B, Ho A, Dolbeare T, Blanchard B, Dee N, Wakeman W, Hirokawa KE, Szafer A, Sunkin SM, Oh SW, Bernard A, Phillips JW, Hawrylycz M, Koch C, Zeng H, Harris JA, Ng L. The Allen Mouse Brain Common Coordinate Framework: A 3D Reference Atlas. Cell 2020; 181:936-953.e20. [PMID: 32386544 PMCID: PMC8152789 DOI: 10.1016/j.cell.2020.04.007] [Citation(s) in RCA: 454] [Impact Index Per Article: 113.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 12/12/2019] [Accepted: 04/03/2020] [Indexed: 01/25/2023]
Abstract
Recent large-scale collaborations are generating major surveys of cell types and connections in the mouse brain, collecting large amounts of data across modalities, spatial scales, and brain areas. Successful integration of these data requires a standard 3D reference atlas. Here, we present the Allen Mouse Brain Common Coordinate Framework (CCFv3) as such a resource. We constructed an average template brain at 10 μm voxel resolution by interpolating high resolution in-plane serial two-photon tomography images with 100 μm z-sampling from 1,675 young adult C57BL/6J mice. Then, using multimodal reference data, we parcellated the entire brain directly in 3D, labeling every voxel with a brain structure spanning 43 isocortical areas and their layers, 329 subcortical gray matter structures, 81 fiber tracts, and 8 ventricular structures. CCFv3 can be used to analyze, visualize, and integrate multimodal and multiscale datasets in 3D and is openly accessible (https://atlas.brain-map.org/).
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Affiliation(s)
- Quanxin Wang
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Song-Lin Ding
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Yang Li
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Josh Royall
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - David Feng
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Phil Lesnar
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Nile Graddis
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Maitham Naeemi
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Benjamin Facer
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Anh Ho
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Tim Dolbeare
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | | | - Nick Dee
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Wayne Wakeman
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | | | - Aaron Szafer
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Susan M Sunkin
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Seung Wook Oh
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Amy Bernard
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | | | | | - Christof Koch
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Hongkui Zeng
- Allen Institute for Brain Science, Seattle, WA 98109, USA
| | - Julie A Harris
- Allen Institute for Brain Science, Seattle, WA 98109, USA.
| | - Lydia Ng
- Allen Institute for Brain Science, Seattle, WA 98109, USA.
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Minderer M, Brown KD, Harvey CD. The Spatial Structure of Neural Encoding in Mouse Posterior Cortex during Navigation. Neuron 2019; 102:232-248.e11. [PMID: 30772081 DOI: 10.1016/j.neuron.2019.01.029] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [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: 06/14/2018] [Revised: 12/01/2018] [Accepted: 01/15/2019] [Indexed: 01/10/2023]
Abstract
Navigation engages many cortical areas, including visual, parietal, and retrosplenial cortices. These regions have been mapped anatomically and with sensory stimuli and studied individually during behavior. Here, we investigated how behaviorally driven neural activity is distributed and combined across these regions. We performed dense sampling of single-neuron activity across the mouse posterior cortex and developed unbiased methods to relate neural activity to behavior and anatomical space. Most parts of the posterior cortex encoded most behavior-related features. However, the relative strength with which features were encoded varied across space. Therefore, the posterior cortex could be divided into discriminable areas based solely on behaviorally relevant neural activity, revealing functional structure in association regions. Multimodal representations combining sensory and movement signals were strongest in posterior parietal cortex, where gradients of single-feature representations spatially overlapped. We propose that encoding of behavioral features is not constrained by retinotopic borders and instead varies smoothly over space within association regions.
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Affiliation(s)
- Matthias Minderer
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Kristen D Brown
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
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Rossi PIA, Musante I, Summa M, Pittaluga A, Emionite L, Ikehata M, Rastaldi MP, Ravazzolo R, Puliti A. Compensatory molecular and functional mechanisms in nervous system of the Grm1(crv4) mouse lacking the mGlu1 receptor: a model for motor coordination deficits. ACTA ACUST UNITED AC 2012; 23:2179-89. [PMID: 22791805 DOI: 10.1093/cercor/bhs200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The metabotropic glutamate type 1 (mGlu1) and type 5 (mGlu5) receptors, the only members of group I mGlu receptors, are implicated in synaptic plasticity and mechanisms of feedback control of glutamate release. They exhibit nearly complementary distributions throughout the central nervous system, well evident in the cerebellum, where mGlu1 receptor is most intensely expressed while mGlu5 receptor is not. Despite their different distribution, they show a similar subcellular localization and use common transducing pathways. We recently described the Grm1(crv4) mouse with motor coordination deficits and renal anomalies caused by a spontaneous mutation inactivating the mGlu1 receptor. To define the neuropathological mechanisms in these mice, we evaluated expression and function of the mGlu5 receptor in cerebral and cerebellar cortices. Western blot and immunofluorescence analyses showed mGlu5 receptor overexpression. Quantitative reverse transcriptase-polymerase chain reaction results indicated that the up-regulation is already evident at RNA level. Functional studies confirmed an enhanced glutamate release from cortical cerebral and cerebellar synaptosomes when compared with wild-type that is abolished by the mGlu5 receptor-specific inhibitor, 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP). Finally, acute MPEP treatment of Grm1(crv4/crv4) mice induced an evident although incomplete improvement of motor coordination, suggesting that mGlu5 receptors enhanced activity worsens, instead of improving, the motor-coordination defects in the Grm1(crv4/crv4) mice.
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Harper EA, Griffin EP, Shankley NP, Black JW. Analysis of the behaviour of selected CCKB/gastrin receptor antagonists in radioligand binding assays performed in mouse and rat cerebral cortex. Br J Pharmacol 1999; 126:1496-503. [PMID: 10217545 PMCID: PMC1565919 DOI: 10.1038/sj.bjp.0702448] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The previously described complex behaviour of the CCKB/gastrin receptor antagonist, L-365,260, in radioligand binding assays could be explained by a variable population of two binding sites. We have investigated whether other CCKB/gastrin receptor ligands (PD134,308, PD140,376, YM022 and JB93182) can distinguish between these sites. 2. In the mouse cortex assay, Hill slopes were not different from unity and the ligand pKI values did not differ when either [125I]-BH-CCK-8S or [3H]-PD140,376 was used as label as expected for a single site (G2). 3. In the rat cortex, where previous analysis of replicate (n=48) L-365,260 data indicated the presence of two CCKB/gastrin sites (G1 and G2), the competition data for PD134,308, PD140,376, YM022 and JB93182 could be explained by a homogeneous population of CCKB/gastrin sites because the Hill slope estimates were not significantly different from unity. However, the estimated affinity values for JB93182 and YM022 were significantly higher and that for PD134,308 was significantly lower than those obtained in the mouse cortex when the same radioligand was used. In view of our previous data obtained with L-365,260, the rat cortex data were also interpreted using a two-site model. In this analysis, SR27897 expressed approximately 9 fold, PD134,308 approximately 13 fold and PD140,376 approximately 11 fold selectivity for the G2 site. In contrast, JB93182 expressed approximately 23 fold and YM022 approximately 4 fold selectivity for the G1 site. If the two-site interpretation of the data is valid then, because of its reverse selectivity to L-365,260, JB93182 has been identified as a compound which if radiolabelled could provide a test of this receptor subdivision.
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Affiliation(s)
- E A Harper
- James Black Foundation, Dulwich, London, England
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