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Martínez-Moreno CG, Calderón-Vallejo D, Harvey S, Arámburo C, Quintanar JL. Growth Hormone (GH) and Gonadotropin-Releasing Hormone (GnRH) in the Central Nervous System: A Potential Neurological Combinatory Therapy? Int J Mol Sci 2018; 19:E375. [PMID: 29373545 PMCID: PMC5855597 DOI: 10.3390/ijms19020375] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 01/21/2018] [Accepted: 01/23/2018] [Indexed: 12/15/2022] Open
Abstract
This brief review of the neurological effects of growth hormone (GH) and gonadotropin-releasing hormone (GnRH) in the brain, particularly in the cerebral cortex, hypothalamus, hippocampus, cerebellum, spinal cord, neural retina, and brain tumors, summarizes recent information about their therapeutic potential as treatments for different neuropathologies and neurodegenerative processes. The effect of GH and GnRH (by independent administration) has been associated with beneficial impacts in patients with brain trauma and spinal cord injuries. Both GH and GnRH have demonstrated potent neurotrophic, neuroprotective, and neuroregenerative action. Positive behavioral and cognitive effects are also associated with GH and GnRH administration. Increasing evidence suggests the possibility of a multifactorial therapy that includes both GH and GnRH.
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Affiliation(s)
- Carlos G Martínez-Moreno
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus Juriquilla, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Querétaro 76230, Mexico.
| | - Denisse Calderón-Vallejo
- Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Av. Universidad 940, Ciudad Universitaria, Aguascalientes 20131, Mexico.
| | - Steve Harvey
- Department of Physiology, University of Alberta, Edmonton, AB T6G 2H7, Canada.
| | - Carlos Arámburo
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Campus Juriquilla, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Querétaro 76230, Mexico.
| | - José Luis Quintanar
- Departamento de Fisiología y Farmacología, Centro de Ciencias Básicas, Universidad Autónoma de Aguascalientes, Av. Universidad 940, Ciudad Universitaria, Aguascalientes 20131, Mexico.
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Harvey S, Martínez-Moreno CG, Luna M, Arámburo C. Autocrine/paracrine roles of extrapituitary growth hormone and prolactin in health and disease: An overview. Gen Comp Endocrinol 2015; 220:103-11. [PMID: 25448258 DOI: 10.1016/j.ygcen.2014.11.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 11/03/2014] [Indexed: 02/07/2023]
Abstract
Growth hormone (GH) and prolactin (PRL) are both endocrines that are synthesized and released from the pituitary gland into systemic circulation. Both are therefore hormones and both have numerous physiological roles mediated through a myriad of target sites and both have pathophysiological consequences when present in excess or deficiency. GH or PRL gene expression is not, however, confined to the anterior pituitary gland and it occurs widely in many of their central and peripheral sites of action. This may reflect "leaky gene" phenomena and the fact that all cells have the potential to express every gene that is present in their genome. However, the presence of GH or PRL receptors in these extrapituitary sites of GH and PRL production suggests that they are autocrine or paracrine sites of GH and PRL action. These local actions often occur prior to the ontogeny of pituitary somatotrophs and lactotrophs and they may complement or differ from the roles of their pituitary counterparts. Many of these local actions are also of physiological significance, since they are impaired by a blockade of local GH or PRL production or by an antagonism of local GH or PRL action. These local actions may also be of pathophysiological significance, since autocrine or paracrine actions of GH and PRL are thought to be causally involved in a number of disease states, particularly in cancer. Autocrine GH for instance, is thought to be more oncogenic than pituitary GH and selective targeting of the autocrine moiety may provide a therapeutic approach to prevent tumor progression. In summary, GH and PRL are not just endocrine hormones, as they have autocrine and/or paracrine roles in health and disease.
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Affiliation(s)
- Steve Harvey
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada.
| | | | - Maricela Luna
- Departamento de Neurobiología, Celular y Molecular Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Qro. 76230, Mexico
| | - Carlos Arámburo
- Departamento de Neurobiología, Celular y Molecular Instituto de Neurobiología, Universidad Nacional Autónoma de México, Querétaro, Qro. 76230, Mexico
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Harvey S, Baudet ML. Extrapituitary growth hormone and growth? Gen Comp Endocrinol 2014; 205:55-61. [PMID: 24746676 DOI: 10.1016/j.ygcen.2014.03.041] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 03/14/2014] [Accepted: 03/24/2014] [Indexed: 11/25/2022]
Abstract
While growth hormone (GH) is obligatory for postnatal growth, it is not required for a number of growth-without-GH syndromes, such as early embryonic or fetal growth. Instead, these syndromes are thought to be dependent upon local growth factors, rather than pituitary GH. The GH gene is, however, also expressed in many extrapituitary tissues, particularly during early development and extrapituitary GH may be one of the local growth factors responsible for embryonic or fetal growth. Moreover, as the expression of the GH receptor (GHR) gene mirrors that of GH in extrapituitary tissues the actions of GH in early development are likely to be mediated by local autocrine or paracrine mechanisms, especially as extrapituitary GH expression occurs prior to the ontogeny of pituitary somatotrophs or the appearance of GH in the circulation. The extrapituitary expression of pituitary somatotrophs or the appearance of GH in the circulation. The extrapituitary expression of GH in embryos has also been shown to be of functional relevance in a number of species, since the immunoneutralization of endogenous GH or the blockade of GH production is accompanied by growth impairment or cellular apoptosis. The extrapituitary expression of the GH gene also persists in some central and peripheral tissues postnatally, which may reflect its continued functional importance and physiological or pathophysiological significance. The expression and functional relevance of extrapituitary GH, particularly during embryonic growth, is the focus of this brief review.
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Affiliation(s)
- Steve Harvey
- Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
| | - Marie-Laure Baudet
- Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Arámburo C, Alba-Betancourt C, Luna M, Harvey S. Expression and function of growth hormone in the nervous system: a brief review. Gen Comp Endocrinol 2014; 203:35-42. [PMID: 24837495 DOI: 10.1016/j.ygcen.2014.04.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 04/18/2014] [Accepted: 04/19/2014] [Indexed: 12/23/2022]
Abstract
There is increasing evidence that growth hormone (GH) expression is not confined exclusively to the pituitary somatotrophs as it is synthesized in many extrapituitary locations. The nervous system is one of those extrapituitary sites. In this brief review we summarize data that substantiate the expression, distribution and characterization of neural GH and detail its roles in neural function, including cellular growth, proliferation, differentiation, neuroprotection and survival, as well as its functional roles in behavior, cognition and neurotransmission. Although systemic GH may exert some of these effects, it is increasingly evident that locally expressed neural GH, acting through intracrine, autocrine or paracrine mechanisms, may also be causally involved as a neurotrophic factor.
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Affiliation(s)
- Carlos Arámburo
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, México.
| | - Clara Alba-Betancourt
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, México
| | - Maricela Luna
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, México
| | - Steve Harvey
- Department of Physiology, University of Alberta, Edmonton T6G 2H7, Canada
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Abstract
GH is best known as an anterior pituitary hormone fundamental in regulating growth, differentiation, and metabolism. GH peptide and mRNA are also present in brain, in which their functions are less well known. Here we describe the distribution of GH neurons and fibers and sex differences in Gh mRNA in adult mouse brain. Cell bodies exhibiting GH immunoreactivity are distributed in many brain regions, particularly in the hypothalamus in which retrograde labeling suggests that some of these cells project to the median eminence. To determine whether Gh mRNA is sexual dimorphic, we carried out quantitative RT-PCR on microdissected brain nuclei. Ovary-intact mice had elevated Gh mRNA in the arcuate nucleus and medial preoptic area (MPOA) compared with gonad-intact males. In males, castration increased Gh mRNA in the MPOA, whereas ovariectomy decreased Gh mRNA in both regions. When gonadectomized adults of both sexes were treated with estradiol Gh mRNA increased in females but had no effect in castrated males. Tamoxifen was able to blunt the rise in Gh mRNA in response to estradiol in females. In addition, we found that estrogen receptor-α is coexpressed in GH neurons in the MPOA and arcuate nucleus. In summary, the findings reveal sexual dimorphisms in Gh gene expression in areas of the brain associated with reproduction and behavior. Interestingly, estradiol enhances Gh mRNA in females only, suggesting that multiple factors orchestrate this sexual dimorphism.
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Affiliation(s)
- Melisande L Addison
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
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Abstract
Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.
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Affiliation(s)
- S Harvey
- Department of Physiology, University of Alberta, 7-41 Medical Sciences Building, Edmonton, AB T6G 2H7, Canada,
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Speakman J, Hambly C, Mitchell S, Król E. The contribution of animal models to the study of obesity. Lab Anim 2008; 42:413-32. [PMID: 18782824 DOI: 10.1258/la.2007.006067] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Obesity results from prolonged imbalance of energy intake and energy expenditure. Animal models have provided a fundamental contribution to the historical development of understanding the basic parameters that regulate the components of our energy balance. Five different types of animal model have been employed in the study of the physiological and genetic basis of obesity. The first models reflect single gene mutations that have arisen spontaneously in rodent colonies and have subsequently been characterized. The second approach is to speed up the random mutation rate artificially by treating rodents with mutagens or exposing them to radiation. The third type of models are mice and rats where a specific gene has been disrupted or over-expressed as a deliberate act. Such genetically-engineered disruptions may be generated through the entire body for the entire life (global transgenic manipulations) or restricted in both time and to certain tissue or cell types. In all these genetically-engineered scenarios, there are two types of situation that lead to insights: where a specific gene hypothesized to play a role in the regulation of energy balance is targeted, and where a gene is disrupted for a different purpose, but the consequence is an unexpected obese or lean phenotype. A fourth group of animal models concern experiments where selective breeding has been utilized to derive strains of rodents that differ in their degree of fatness. Finally, studies have been made of other species including non-human primates and dogs. In addition to studies of the physiological and genetic basis of obesity, studies of animal models have also informed us about the environmental aspects of the condition. Studies in this context include exploring the responses of animals to high fat or high fat/high sugar (Cafeteria) diets, investigations of the effects of dietary restriction on body mass and fat loss, and studies of the impact of candidate pharmaceuticals on components of energy balance. Despite all this work, there are many gaps in our understanding of how body composition and energy storage are regulated, and a continuing need for the development of pharmaceuticals to treat obesity. Accordingly, reductions in the use of animal models, while ethically desirable, will not be feasible in the short to medium term, and indeed an expansion in activity using animal models is anticipated as the epidemic continues and spreads geographically.
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Affiliation(s)
- John Speakman
- Aberdeen Centre for Energy Regulation and Obesity, School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK.
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Frick F, Hume R, Robinson IC, Edén S, Oscarsson J. Hepatic and adipose tissue depot-specific changes in lipid metabolism in Late-onset Obese (LOB) rats. Lipids 2008; 43:313-24. [PMID: 18335266 DOI: 10.1007/s11745-008-3164-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 02/19/2008] [Indexed: 01/22/2023]
Abstract
Transgenic Late-onset OBesity (LOB) rats slowly develop a male-specific, autosomal dominant, obesity phenotype with a specific increase in peri-renal white adipose tissue (WAT) depot and preserved insulin sensitivity (Bains et al. in Endocrinology 145:2666-2679, 2004). To better understand the remarkable phenotype of these rats, the lipid metabolism was investigated in male LOB and non-transgenic (NT) littermates. Total plasma cholesterol (C) levels were normal but total plasma triacylglycerol (TAG) (2.8-fold) and hepatic TAG content (25%) was elevated in LOB males. Plasma VLDL-C and VLDL-TAG levels were higher while plasma apoB levels were 60% lower in LOB males. Increased hepatic TAG secretion explained the increased VLDL levels in LOB males. The hepatic gene expression of FAS, SCD-1, mitochondrial (mt)GPAT, and DGAT2 was up-regulated in both old obese and young non-obese LOB rats. Lipoprotein lipase (LPL) activity in heart and epididymal white adipose tissue (WAT) was unchanged, while LPL activity was increased in peri-renal WAT (30%) and decreased in soleus muscle (40%). Moreover, FAS, SCD-1 and DGAT2 gene expression was increased in peri-renal, but not in epididymal WAT. Basal lipolysis was reduced or unchanged and beta-adrenergic stimulated lipolysis was reduced in WAT from both old obese and young non-obese LOB rats. To summarize, the obese phenotype of LOB male rats is associated with increased hepatic TAG production and secretion, a shift in LPL activity from skeletal muscle to WAT, reduced lipolytic response in WAT depots and a specific increase in expression of genes responsible for fatty acid and TAG synthesis in the peri-renal depot.
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Affiliation(s)
- Fredrik Frick
- Department of Bioscience, AstraZeneca R&D, Pepparedsleden 1, 431 83, Mölndal, Sweden.
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Martin NM, Houston PA, Patterson M, Sajedi A, Carmignac DF, Ghatei MA, Bloom SR, Small CJ. Abnormalities of the somatotrophic axis in the obese agouti mouse. Int J Obes (Lond) 2006; 30:430-8. [PMID: 16172617 DOI: 10.1038/sj.ijo.0803076] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Abnormalities of the melanocortin system produce obesity and increased linear growth. While the obesity phenotype is well characterised, the mechanism responsible for increased linear growth is unclear. The somatotrophic axis was studied in the obese agouti (A(y)/a) mouse as a model of a perturbed melanocortin system. DESIGN Adult obese A(y)/a mice were compared to age- and sex-matched wild-type (WT) controls. Weight and body length (nose-anus) were recorded. Plasma growth hormone (GH), insulin-like growth factor-I (IGFI), insulin and leptin were measured using radioimmunoassay. Since ghrelin is a potent GH secretagogue, plasma ghrelin, stomach ghrelin peptide and stomach ghrelin mRNA expression were studied. Hypothalamic periventricular (PeVN) somatostatin neurones and arcuate (Arc) neuropeptide Y (NPY) neurones inhibit the growth axis, whereas Arc growth hormone-releasing hormone (GHRH) neurones are stimulatory. Therefore, specific hypothalamic expression of somatostatin, NPY and GHRH was measured using quantitative in situ hybridisation. RESULTS Obese A(y)/a mice were significantly heavier and longer than WT controls. Plasma IGFI concentrations were 30% greater in obese A(y)/a mice. Obese A(y) /a mice were hyperinsulinaemic and hyperleptinaemic, yet plasma ghrelin, and stomach ghrelin peptide and mRNA were significantly reduced. In obese A(y)/a mice, PeVN somatostatin and Arc NPY mRNA expression were reduced by 50% compared to WT controls, whereas Arc GHRH mRNA expression was unchanged. CONCLUSION Increased body length in adult obese A(y)/a mice may result from reduced Arc NPY and PeVN somatostatin mRNA expression, which in turn, may increase plasma IGFI concentrations and upregulate the somatotrophic axis.
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Affiliation(s)
- N M Martin
- Department of Metabolic Medicine, Imperial College at Hammersmith Campus, Du Cane Road, London W12 0NN, UK
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Tesson L, Cozzi J, Ménoret S, Rémy S, Usal C, Fraichard A, Anegon I. Transgenic modifications of the rat genome. Transgenic Res 2006; 14:531-46. [PMID: 16245144 DOI: 10.1007/s11248-005-5077-z] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Accepted: 03/29/2005] [Indexed: 11/28/2022]
Abstract
The laboratory rat (R. norvegicus) is a very important experimental animal in several fields of biomedical research. This review describes the various techniques that have been used to generate transgenic rats: classical DNA microinjection and more recently described techniques such as lentiviral vector-mediated DNA transfer into early embryos, sperm-mediated transgenesis, embryo cloning by nuclear transfer and germline mutagenesis. It will also cover techniques associated to transgenesis such as sperm cryopreservation, embryo freezing and determination of zygosity. The availability of several technologies allowing genetic manipulation in the rat coupled to genomic data will allow biomedical research to fully benefit from the rat as an experimental animal.
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Affiliation(s)
- Laurent Tesson
- Institut de Transplantation et de Recherche en Transplantation (ITERT), F-44093, Nantes, France
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Bains RK, Wells SE, Flavell DM, Fairhall KM, Strom M, Le Tissier P, Robinson ICAF. Visceral obesity without insulin resistance in late-onset obesity rats. Endocrinology 2004; 145:2666-79. [PMID: 15033913 DOI: 10.1210/en.2003-1608] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We describe a line of transgenic rats in which the males develop a unique autosomal dominant, late-onset obesity (LOB) phenotype. LOB males gradually accumulate fat specifically in visceral, but not peripheral, fat depots despite a normal intake of a low fat diet. LOB females normally develop only mild obesity with advanced age. However, the phenotype can be induced rapidly in young females by ovariectomy and prevented by estrogen replacement. LOB males are highly sensitive to dietary fat. Young, nonobese LOB males gain more weight on a 30% fat diet and lose more weight when treated with the lipase inhibitor, Orlistat, than their nontransgenic littermates. Remarkably, despite severe visceral obesity, LOB rats have normal fasting blood glucose, insulin, and corticosterone; show normal or increased insulin sensitivity in glucose and insulin tolerance tests; have increased plasma adiponectin levels; and display a heightened response to treatment with rosiglitazone. Their visceral adiposity reflects a specific increase in visceral adipocyte number, not size. Analysis of the transgene in LOB rats revealed a deletion in the gene encoding the S26 subunit of the mitochondrial ribosome that results in the production of a truncated protein, which we show to be imported into mitochondria. However, the transgene integrant is complex, so whether this is the sole molecular disruption underlying this phenotype remains to be established. Nevertheless, LOB rats provide a valuable new model of late-onset, male-preponderant, visceral-specific obesity, clearly dissociated from insulin resistance.
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Affiliation(s)
- Randip K Bains
- Division of Molecular Neuroendocrinology, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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Gainer H. Transgenic models for molecular and physiological studies in the central nervous system. J Physiol 2003; 551:3. [PMID: 12813155 PMCID: PMC2343151 DOI: 10.1113/jphysiol.2003.040840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Harold Gainer
- Laboratory of Neurochemistry, National Institutes of Neurological Diseases and Stroke/NIH, Bethesda, MD 20892, USA.
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