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Levin LA, Chiang MF, Dyer MA, Greenwell TN, Svendsen CN, Tumminia SJ, Van Gelder RN, Wong RO. Translational roadmap for regenerative therapies of eye disease. Med 2023; 4:583-590. [PMID: 37689055 PMCID: PMC10793077 DOI: 10.1016/j.medj.2023.06.005] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 06/07/2023] [Accepted: 06/12/2023] [Indexed: 09/11/2023]
Abstract
The translation of regenerative therapies to neuronal eye diseases requires a roadmap specific to the nature of the target diseases, patient population, methodologies for assessing outcome, and other factors. This commentary focuses on critical issues for translating regenerative eye therapies relevant to retinal neurons to human clinical trials.
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Affiliation(s)
- Leonard A Levin
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, QC H3A2B4, Canada; Department of Neurology & Neurosurgery, McGill University, Montreal, QC H3A2B4, Canada.
| | - Michael F Chiang
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA; National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude's Research Hospital, Memphis, TN 38105, USA
| | - Thomas N Greenwell
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Clive N Svendsen
- Board of Governors Regenerative Medicine Institute, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA; Department of Biomedical Sciences, Cedars Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Santa J Tumminia
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Russell N Van Gelder
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Pathology and Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA; Roger and Angie Karalis Johnson Retina Center, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Rachel O Wong
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Biological Structure, University of Washington School of Medicine, Seattle, WA 98195, USA
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Fortress AM, Miyagishima KJ, Reed AA, Temple S, Clegg DO, Tucker BA, Blenkinsop TA, Harb G, Greenwell TN, Ludwig TE, Bharti K. Stem cell sources and characterization in the development of cell-based products for treating retinal disease: An NEI Town Hall report. Stem Cell Res Ther 2023; 14:53. [PMID: 36978104 PMCID: PMC10053463 DOI: 10.1186/s13287-023-03282-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [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: 11/09/2022] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
National Eye Institute recently issued a new Strategic Plan outlining priority research areas for the next 5 years. Starting cell source for deriving stem cell lines is as an area with gaps and opportunities for making progress in regenerative medicine, a key area of emphasis within the NEI Strategic Plan. There is a critical need to understand how starting cell source affects the cell therapy product and what specific manufacturing capabilities and quality control standards are required for autologous vs allogeneic stem cell sources. With the goal of addressing some of these questions, in discussion with the community-at-large, NEI hosted a Town Hall at the Association for Research in Vision and Ophthalmology annual meeting in May 2022. This session leveraged recent clinical advances in autologous and allogeneic RPE replacement strategies to develop guidance for upcoming cell therapies for photoreceptors, retinal ganglion cells, and other ocular cell types. Our focus on stem cell-based therapies for RPE underscores the relatively advanced stage of RPE cell therapies to patients with several ongoing clinical trials. Thus, this workshop encouraged lessons learned from the RPE field to help accelerate progress in developing stem cell-based therapies in other ocular tissues. This report provides a synthesis of the key points discussed at the Town Hall and highlights needs and opportunities in ocular regenerative medicine.
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Affiliation(s)
- Ashley M Fortress
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
| | | | - Amberlynn A Reed
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | | | - Dennis O Clegg
- Center for Stem Cell Biology and Engineering, University of California, Santa Barbara, CA, USA
| | - Budd A Tucker
- Institute for Vision Research, Department of Ophthalmology and Visual Science, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Timothy A Blenkinsop
- Ophthalmology Cell Development and Regenerative Biology, Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | | | - Thomas N Greenwell
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
| | | | - Kapil Bharti
- Ocular and Stem Cell Translational Research, National Eye Institute, NIH, Bethesda, MD, USA.
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Van Gelder RN, Chiang MF, Dyer MA, Greenwell TN, Levin LA, Wong RO, Svendsen CN. Author Correction: Regenerative and restorative medicine for eye disease. Nat Med 2022; 28:2218. [PMID: 35945286 DOI: 10.1038/s41591-022-01996-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Russell N Van Gelder
- Karalis-Johnson Retina Center, Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA, USA. .,Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA. .,Department of Pathology and Laboratory Medicine, University of Washington School of Medicine, Seattle, WA, USA. .,Roger and Angie Karalis Johnson Retina Center, University of Washington School of Medicine, Seattle, WA, USA.
| | - Michael F Chiang
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude's Research Hospital, Memphis, TN, USA
| | - Thomas N Greenwell
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Leonard A Levin
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Quebec, Canada.,Department of Neurology & Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - Rachel O Wong
- Karalis-Johnson Retina Center, Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA, USA.,Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA
| | - Clive N Svendsen
- Board of Governors Regenerative Medicine Institute, Los Angeles, CA, USA.,Department of Biomedical Sciences, Cedars Sinai Medical Center, Los Angeles, CA, USA
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Van Gelder RN, Chiang MF, Dyer MA, Greenwell TN, Levin LA, Wong RO, Svendsen CN. Regenerative and restorative medicine for eye disease. Nat Med 2022; 28:1149-1156. [PMID: 35715505 PMCID: PMC10718186 DOI: 10.1038/s41591-022-01862-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [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] [Received: 02/14/2022] [Accepted: 05/06/2022] [Indexed: 12/11/2022]
Abstract
Causes of blindness differ across the globe; in higher-income countries, most blindness results from the degeneration of specific classes of cells in the retina, including retinal pigment epithelium (RPE), photoreceptors, and retinal ganglion cells. Advances over the past decade in retinal regenerative medicine have allowed each of these cell types to be produced ex vivo from progenitor stem cells. Here, we review progress in applying these technologies to cell replacement - with the goal of vision restoration in degenerative disease. We discuss the landscape of human clinical trials for RPE transplantation and advanced preclinical studies for other cell types. We also review progress toward in situ repair of retinal degeneration using endogenous progenitor cells. Finally, we provide a high-level overview of progress toward prosthetic ocular vision restoration, including advanced photovoltaic devices, opsin-based gene therapy, and small-molecule photoswitches. Progress in each of these domains is at or near the human clinical-trial stage, bringing the audacious goal of vision restoration within sight.
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Affiliation(s)
- Russell N Van Gelder
- Karalis-Johnson Retina Center, Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA, USA.
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA.
- Department of Pathology and Laboratory Medicine, University of Washington School of Medicine, Seattle, WA, USA.
- Roger and Angie Karalis Johnson Retina Center, University of Washington School of Medicine, Seattle, WA, USA.
| | - Michael F Chiang
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Michael A Dyer
- Department of Developmental Neurobiology, St. Jude's Research Hospital, Memphis, TN, USA
| | - Thomas N Greenwell
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Leonard A Levin
- Department of Ophthalmology and Visual Sciences, McGill University, Montreal, Quebec, Canada
- Department of Neurology & Neurosurgery, McGill University, Montreal, Quebec, Canada
| | - Rachel O Wong
- Karalis-Johnson Retina Center, Department of Ophthalmology, University of Washington School of Medicine, Seattle, WA, USA
- Department of Biological Structure, University of Washington School of Medicine, Seattle, WA, USA
| | - Clive N Svendsen
- Board of Governors Regenerative Medicine Institute, Los Angeles, CA, USA
- Department of Biomedical Sciences, Cedars Sinai Medical Center, Los Angeles, CA, USA
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O’Mara A, Rowland JH, Greenwell TN, Wiggs CL, Fleg J, Joseph L, McGowan J, Panagis JS, Washabaugh C, Peng GCY, Bray R, Cernich AN, Cruz TH, Marden S, Michel ME, Nitkin R, Quatrano L, Spong CY, Shekim L, Jones TLZ, Juliano-Bult D, Panchinson DM, Chen D, Jakeman L, Knebel A, Tully LA, Chan L, Damiano D, Tian B, McInnes P, Khalsa P, Reider E, Shurtleff D, Elwood W, Ballard R, Ershow AG, Begg L. National Institutes of Health Research Plan on Rehabilitation: NIH Medical Rehabilitation Coordinating Committee. Phys Ther 2017; 97:104-407. [PMID: 28499003 PMCID: PMC5436691 DOI: 10.1093/ptj/pzx026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
One in five Americans experiences disability that affects their daily function because of impairments in mobility, cognitive function, sensory impairment, or communication impairment. The need for rehabilitation strategies to optimize function and reduce disability is a clear priority for research to address this public health challenge. The National Institutes of Health (NIH) recently published a Research Plan on Rehabilitation that provides a set of priorities to guide the field over the next 5 years. The plan was developed with input from multiple Institutes and Centers within the NIH, the National Advisory Board for Medical Rehabilitation Research, and the public. This article provides an overview of the need for this research plan, an outline of its development, and a listing of six priority areas for research. The NIH is committed to working with all stakeholder communities engaged in rehabilitation research to track progress made on these priorities and to work to advance the science of medical rehabilitation.This article is being published almost simultaneously in the following six journals: American Journal of Occupational Therapy, American Journal of Physical Medicine and Rehabilitation, Archives of Physical Medicine and Rehabilitation, Neurorehabilitation and Neural Repair, Physical Therapy, and Rehabilitation Psychology. Citation information is as follows: NIH Medical Rehabilitation Coordinating Committee. Am J Phys Med Rehabil. 2017;97(4):404-407.
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Affiliation(s)
| | | | | | | | | | - Jerome Fleg
- National Heart, Lung, and Blood Institute (NHLBI)
| | | | - Joan McGowan
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
| | - James S. Panagis
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
| | - Charles Washabaugh
- National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
| | - Grace C. Y. Peng
- National Institute of Biomedical Imaging and Bioengineering (NIBIB)
| | - Rosalina Bray
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Alison N. Cernich
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Theresa H. Cruz
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Sue Marden
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Mary Ellen Michel
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Ralph Nitkin
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Louis Quatrano
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Catherine Y. Spong
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)
| | - Lana Shekim
- National Institute on Deafness and Other Communication Disorders (NIDCD)
| | - Teresa L. Z. Jones
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
| | | | | | - Daofen Chen
- National Institute of Neurological Disorders and Stroke (NINDS)
| | - Lyn Jakeman
- National Institute of Neurological Disorders and Stroke (NINDS)
| | - Ann Knebel
- National Institute of Nursing Research (NINR)
| | | | | | | | | | - Pamela McInnes
- National Center for Advancing Translational Sciences (NCATS)
| | - Partap Khalsa
- National Center for Complementary and Integrative Health (NCCIH)
| | - Eve Reider
- National Center for Complementary and Integrative Health (NCCIH)
| | - David Shurtleff
- National Center for Complementary and Integrative Health (NCCIH)
| | - William Elwood
- Offices of the Director, Division of Program Coordination, Planning, and Strategic Initiatives (DPCPSI)
| | | | | | - Lisa Begg
- Office of Research on Women's Health (ORWH)—all in Bethesda, MD
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Vendruscolo LF, Schlosburg JE, Misra KK, Chen SA, Greenwell TN, Koob GF. Escalation patterns of varying periods of heroin access. Pharmacol Biochem Behav 2011; 98:570-4. [PMID: 21406200 DOI: 10.1016/j.pbb.2011.03.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 03/03/2011] [Accepted: 03/04/2011] [Indexed: 11/18/2022]
Abstract
The prevalence of opioid abuse and dependence has been on the rise in just the past few years. Animal studies indicate that extended access to heroin produces escalation of intake over time, whereas stable intake is observed under limited-access conditions. Escalation of drug intake has been suggested to model the transition from controlled drug use to compulsive drug seeking and taking. Here, we directly compared the pattern of heroin intake in animals with varying periods of heroin access. Food intake was also monitored over the course of escalation. Rats were allowed to lever press on a fixed-ratio 1 schedule of reinforcement to receive intravenous infusions of heroin for 1, 6, 12, or 23h per day for 14 sessions. The results showed that heroin intake in the 12 and 23h groups markedly increased over time, whereas heroin intake in the 1h group was stable. The 6h group showed a significant but modest escalation of intake. Total heroin intake was similar in the 12 and 23h groups, but the rate of heroin self-administration was two-fold higher in the 12h group compared with the 23h group. Food intake decreased over sessions only in the 12h group. The 12 and 23h groups showed marked physical signs of naloxone-precipitated withdrawal. These findings suggest that 12h heroin access per day may be the optimal access time for producing escalation of heroin intake. The advantages of this model and the potential relevance for studying drug addiction are discussed.
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Affiliation(s)
- Leandro F Vendruscolo
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA92037, USA
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Greenwell TN, Funk CK, Cottone P, Richardson HN, Chen SA, Rice KC, Zorrilla EP, Koob GF. Corticotropin-releasing factor-1 receptor antagonists decrease heroin self-administration in long- but not short-access rats. Addict Biol 2009; 14:130-43. [PMID: 19291009 DOI: 10.1111/j.1369-1600.2008.00142.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [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: 11/28/2022]
Abstract
Dysregulation of the stress-related corticotropin-releasing factor (CRF) system has been implicated in the development of drug dependence. The present study examined the effects of administering CRF type 1 (CRF(1)) receptor antagonists on heroin self-administration in animals allowed short (1 hour) or long (8-12 hours) access to intravenous heroin self-administration sessions. The nonpeptide CRF(1) antagonists MJL-1-109-2 (1 hour versus 8 hours access) or R121919 (1 hour versus 12 hours access) were systemically injected in both short- and long-access rats. MJL-1-109-2 (10 mg/kg) and R121919 (10 and 20 mg/kg) reduced heroin self-administration in long-access animals without altering heroin intake in short-access animals. Both MJL-1-109-2 and R121919 decreased first-hour intravenous heroin self-administration selectively in long-access rats, with R121919 decreasing cumulative heroin intake across the 12-hour session. The results demonstrate that blockade of the CRF-CRF(1) receptor system attenuates the increased heroin intake of rats with extended access to the drug.
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Affiliation(s)
- Thomas N Greenwell
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, USA
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Greenwell TN, Martin-Schild S, Inglis FM, Zadina JE. Colocalization and shared distribution of endomorphins with substance P, calcitonin gene-related peptide, gamma-aminobutyric acid, and the mu opioid receptor. J Comp Neurol 2007; 503:319-33. [PMID: 17492626 DOI: 10.1002/cne.21374] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [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: 11/07/2022]
Abstract
The endomorphins are endogenous opioids with high affinity and selectivity for the mu opioid receptor (MOR, MOR-1, MOP). Endomorphin-1 (Tyr-Pro-Trp-Phe-NH(2); EM1) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2); EM2) have been localized to many regions of the central nervous system (CNS), including those that regulate antinociception, autonomic function, and reward. Colocalization or shared distribution (overlap) of two neurotransmitters, or a transmitter and its cognate receptor, may imply an interaction of these elements in the regulation of functions mediated in that region. For example, previous evidence of colocalization of EM2 with substance P (SP), calcitonin gene-related peptide (CGRP), and MOR in primary afferent neurons suggested an interaction of these peptides in pain modulation. We therefore investigated the colocalization of EM1 and EM2 with SP, CGRP, and MOR in other areas of the CNS. EM2 was colocalized with SP and CGRP in the nucleus of the solitary tract (NTS) and with SP, CGRP and MOR in the parabrachial nucleus. Several areas in which EM1 and EM2 showed extensive shared distributions, but no detectable colocalization with other signaling molecules, are also described.
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Affiliation(s)
- Thomas N Greenwell
- Neuroscience Program, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA
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Chen SA, O'Dell LE, Hoefer ME, Greenwell TN, Zorrilla EP, Koob GF. Unlimited access to heroin self-administration: independent motivational markers of opiate dependence. Neuropsychopharmacology 2006; 31:2692-707. [PMID: 16452993 DOI: 10.1038/sj.npp.1301008] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The goal of the present study was to develop and validate an animal model of unlimited access to intravenous heroin self-administration combined with responding for food and water to characterize the transition to drug dependence. Male Wistar rats were allowed to lever press for heroin (60 microg/kg/0.1 ml infusion/s; fixed ratio 1; 20-s time out) and nosepoke for food and water in consecutive, daily 23-h sessions. Daily heroin intake increased over days, reaching significance by Day 14. Drug-taking increased across the circadian cycle, reflected as increases in both the nocturnal peak and diurnal nadir of heroin intake. Changes in the circadian pattern of food intake and meal patterning preceded and paralleled the changes in heroin intake. By Day 7, the circadian amplitude of feeding was blunted. Nocturnal intake decreased because rats consumed smaller and briefer meals. Diurnal intake increased due to increased meal frequency, whereas total daily food intake decreased. To control for time or experience in the self-administration boxes as a possible confound, rats with saline (no drug) tethers were tested and did not display significant changes in food intake pattern. Body weight gain slowed slightly in heroin rats relative to saline controls. Separate groups of rats revealed that significant physical dependence as measured by physical signs of opiate withdrawal following a naloxone injection (1.0 mg/kg, subcutaneous (s.c.)) was reached by Day 14. Significant increases in heroin intake could be produced using low doses of naloxone (0.003-0.03 mg/kg, s.c.) on days 28-31 of heroin access. After 6 weeks of heroin self-administration, rats injected with buprenorphine (0, 0.01, 0.04, and 0.2 mg/kg, s.c.) showed a dose-dependent reduction in heroin intake. Changes in the pattern of drug and food intake in the present unlimited heroin access model may serve as independent motivational markers for the transition to a drug-dependent state.
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Affiliation(s)
- Scott A Chen
- Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA, USA.
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Abstract
Many different neuropharmacological agents modulate arousal and anxiety, yet to date, few endogenous substances have produced arousal with an anxiolytic effect. In this issue of Neuron, Xu et al. describe the localization and characterization of a novel neuropeptide, neuropeptide S (and its cognate receptor), that is unique in its arousing and anxiolytic-like properties.
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Affiliation(s)
- George F Koob
- Department of Neuropharmacology, The Scripps Research Institute, La Jolla, California 92037, USA
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Greenwell TN, Zangen A, Martin-Schild S, Wise RA, Zadina JE. Endomorphin-1 and -2 immunoreactive cells in the hypothalamus are labeled by fluoro-gold injections to the ventral tegmental area. J Comp Neurol 2002; 454:320-8. [PMID: 12442322 DOI: 10.1002/cne.10464] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [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: 12/23/2022]
Abstract
Endomorphin-1 and -2 (EM1, EM2) are endogenous opioids with high affinity and selectivity for the mu-opioid receptor. Cells expressing EM-like immunoreactivity (EM-LI) are present in the hypothalamus, and fibers containing EM-LI project to many brain regions, including the ventral tegmental area (VTA). The VTA is one of the most sensitive brain regions for the rewarding and locomotor effects of opioids. It contains mu-opioid receptors, which are thought to mediate gamma-aminobutyric acid-dependent disinhibition of dopamine transmission to the nucleus accumbens. We investigated whether hypothalamic EM-LI cells project to the VTA, where they could play a natural role in this circuitry. The retrograde tracer Fluoro-Gold (FG) was microinjected into the anterior or posterior VTA in rats. Nine days later, colchicine was injected, and 24 hours later, the animals were perfused and processed for fluorescence immunocytochemistry. Numerous FG-labeled cells were detected in the hypothalamus. Both EM1-LI and EM2-LI cells were present in the periventricular nucleus, between the dorsomedial and ventromedial hypothalamus and between the ventromedial and arcuate nuclei. Subpopulations of EM1-LI and EM2-LI cells were labeled by FG. Injections of FG to the anterior and posterior VTA were both effective in producing double-labeled cells, and an anterior-posterior topographical organization between the VTA and hypothalamus was observed. The results support the idea that some endomorphin-containing neurons in the hypothalamus project to the VTA, where they may modulate reward and locomotor circuitry.
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Affiliation(s)
- Thomas N Greenwell
- Neuroscience Program, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA
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