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Zhou H, Wang K, Xu Z, Liu D, Wang Y, Guo M. Chronic unpredictable stress induces depression/anxiety-related behaviors and alterations of hippocampal monoamine receptor mRNA expression in female mice at different ages. Heliyon 2023; 9:e18369. [PMID: 37539192 PMCID: PMC10393760 DOI: 10.1016/j.heliyon.2023.e18369] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 07/11/2023] [Accepted: 07/14/2023] [Indexed: 08/05/2023] Open
Abstract
Depression and anxiety are the most common mental health disorders. Though they affect people at any age and occur more often in females, the pathophysiological changes under these conditions are less investigated. In the present study, we examined the effects of age and stress on depression- and anxiety-related behaviors in female mice. Saccharin preference and the open field test were carried out before and after chronic unpredictable stress in 4-, 14- and 25-month-old female mice. After behavioral tests, mRNA levels of monoamine receptors in the hippocampus were measured by real-time RT-PCR. Chronic unpredictable stress decreased saccharin preference in 4-, 14- and 25-month-old mice and the time spent in the center in the open field test in 25-month-old mice. For monoamine receptors, analysis of variance revealed significant effects of age on mRNA levels of Htr1a, Htr2a, Htr6, Adra1a, Adrb2, and Adrb3, significant effects of stress on mRNA levels of Htr4, Adra2c, Adrb1, and Adrb2, and interactions of age × stress on mRNA levels of Htr1a, Htr5b, Adra1d, Adra2a, Adra2c, and Adrb1. Chronic unpredictable stress decreased mRNA levels of Htr4, Htr5b, Adra2c, and Adrb1 in 4-month-old female mice. Correlations were observed between saccharin preference and mRNA levels of Htr4, Htr5b, Htr6, Adra1d, Adra2a, and Adra2c in 4-month-old mice and between the time spent in the center in the open field test and mRNA levels of Htr1b in 4-month-old mice, Htr3a, Htr7, and Adrb2 in 14-month-old mice, and Drd2 in 4- and 14-month-old mice. Our findings support that stress induces depression- and anxiety-related behaviors and the expression of hippocampal monoamine receptors in an age-dependent manner in female mice.
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Affiliation(s)
- Han Zhou
- Department of Psychology, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
| | - Kaixin Wang
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
| | - Zhicheng Xu
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
| | - Dunjiang Liu
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
| | - Yameng Wang
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
| | - Ming Guo
- Department of Psychology, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
- Medical Research Center, Binzhou Medical University Hospital, The First School of Clinical Medicine of Binzhou Medical University, Binzhou, Shandong, 256603, China
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Laurencin C, Lancelot S, Merida I, Costes N, Redouté J, Le Bars D, Boulinguez P, Ballanger B. Distribution of α 2-Adrenergic Receptors in the Living Human Brain Using [ 11C]yohimbine PET. Biomolecules 2023; 13:biom13050843. [PMID: 37238713 DOI: 10.3390/biom13050843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 05/28/2023] Open
Abstract
The neurofunctional basis of the noradrenergic (NA) system and its associated disorders is still very incomplete because in vivo imaging tools in humans have been missing up to now. Here, for the first time, we use [11C]yohimbine in a large sample of subjects (46 healthy volunteers, 23 females, 23 males; aged 20-50) to perform direct quantification of regional alpha 2 adrenergic receptors' (α2-ARs) availability in the living human brain. The global map shows the highest [11C]yohimbine binding in the hippocampus, the occipital lobe, the cingulate gyrus, and the frontal lobe. Moderate binding was found in the parietal lobe, thalamus, parahippocampus, insula, and temporal lobe. Low levels of binding were found in the basal ganglia, the amygdala, the cerebellum, and the raphe nucleus. Parcellation of the brain into anatomical subregions revealed important variations in [11C]yohimbine binding within most structures. Strong heterogeneity was found in the occipital lobe, the frontal lobe, and the basal ganglia, with substantial gender effects. Mapping the distribution of α2-ARs in the living human brain may prove useful not only for understanding the role of the NA system in many brain functions, but also for understanding neurodegenerative diseases in which altered NA transmission with specific loss of α2-ARs is suspected.
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Affiliation(s)
- Chloé Laurencin
- Université de Lyon, 69622 Lyon, France
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
- INSERM U1028, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- CNRS UMR5292, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- Hôpital Neurologique Pierre Wertheimer, Service de Neurologie C, Centre Expert Parkinson, Hospices Civils de Lyon, 69677 Bron, France
| | - Sophie Lancelot
- Université de Lyon, 69622 Lyon, France
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
- INSERM U1028, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- CNRS UMR5292, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- CERMEP-Imagerie du Vivant, 69500 Bron, France
- Hospices Civils de Lyon, 69677 Bron, France
| | - Inès Merida
- CERMEP-Imagerie du Vivant, 69500 Bron, France
| | | | | | - Didier Le Bars
- CERMEP-Imagerie du Vivant, 69500 Bron, France
- Hospices Civils de Lyon, 69677 Bron, France
| | - Philippe Boulinguez
- Université de Lyon, 69622 Lyon, France
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
- INSERM U1028, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- CNRS UMR5292, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
| | - Bénédicte Ballanger
- Université de Lyon, 69622 Lyon, France
- Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
- INSERM U1028, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
- CNRS UMR5292, Lyon Neuroscience Research Center (CRNL), 69000 Lyon, France
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Guzmán-Ramos K, Osorio-Gómez D, Bermúdez-Rattoni F. Cognitive impairment in alzheimer’s and metabolic diseases: A catecholaminergic hypothesis. Neuroscience 2022; 497:308-323. [DOI: 10.1016/j.neuroscience.2022.05.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 05/19/2022] [Accepted: 05/24/2022] [Indexed: 12/16/2022]
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The Novel Alpha-2 Adrenoceptor Inhibitor Beditin Reduces Cytotoxicity and Huntingtin Aggregates in Cell Models of Huntington's Disease. Pharmaceuticals (Basel) 2021; 14:ph14030257. [PMID: 33809220 PMCID: PMC7998230 DOI: 10.3390/ph14030257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 03/06/2021] [Accepted: 03/08/2021] [Indexed: 11/17/2022] Open
Abstract
Huntington's disease (HD) is a monogenetic neurodegenerative disorder characterized by the accumulation of polyglutamine-expanded huntingtin (mHTT). There is currently no cure, and therefore disease-slowing remedies are sought to alleviate symptoms of the multifaceted disorder. Encouraging findings in Alzheimer's and Parkinson's disease on alpha-2 adrenoceptor (α2-AR) inhibition have shown neuroprotective and aggregation-reducing effects in cell and animal models. Here, we analyzed the effect of beditin, a novel α2- adrenoceptor (AR) antagonist, on cell viability and mHTT protein levels in cell models of HD using Western blot, time-resolved Foerster resonance energy transfer (TR-FRET), lactate dehydrogenase (LDH) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) cytotoxicity assays. Beditin decreases cytotoxicity, as measured by TUNEL staining and LDH release, in a neuronal progenitor cell model (STHdh cells) of HD and decreases the aggregation propensity of HTT exon 1 fragments in an overexpression model using human embryonic kidney (HEK) 293T cells. α2-AR is a promising therapeutic target for further characterization in HD models. Our data allow us to suggest beditin as a valuable candidate for the pharmaceutical manipulation of α2-AR, as it is capable of modulating neuronal cell survival and the level of mHTT.
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Krzyczmonik A, Keller T, López-Picón FR, Forsback S, Kirjavainen AK, Takkinen JS, Wasilewska A, Scheinin M, Haaparanta-Solin M, Sączewski F, Solin O. Radiosynthesis and Preclinical Evaluation of an α 2A-Adrenoceptor Tracer Candidate, 6-[ 18F]Fluoro-marsanidine. Mol Imaging Biol 2020; 21:879-887. [PMID: 30710261 DOI: 10.1007/s11307-019-01317-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE The α2-adrenoceptors mediate many effects of norepinephrine and epinephrine, and participate in the regulation of neuronal, endocrine, cardiovascular, vegetative, and metabolic functions. Of the three receptor subtypes, only α2A and α2C are found in the brain in significant amounts. Subtype-selective positron emission tomography (PET) imaging of α2-adrenoceptors has been limited to the α2C subtype. Here, we report the synthesis of 6-[18F]fluoro-marsanidine, a subtype-selective PET tracer candidate for α2A-adrenoceptors, and its preclinical evaluation in rats and mice. PROCEDURES 6-[18F]Fluoro-marsanidine was synthesized using electrophilic F-18 fluorination with [18F]Selectfluor bis(triflate). The tracer was evaluated in Sprague Dawley rats and in α2A-knockout (KO) and wild-type (WT) mice for subtype selectivity. In vivo PET imaging and ex vivo brain autoradiography were performed to determine the tracer distribution in the brain. The specificity of the tracer for the target was determined by pretreatment with the subtype-non-selective α2-agonist medetomidine. The peripheral biodistribution and extent of metabolism of 6-[18F]fluoro-marsanidine were also analyzed. RESULTS 6-[18F]Fluoro-marsanidine was synthesized with [18F]Selectfluor bis(triflate) in a radiochemical yield of 6.4 ± 1.7 %. The molar activity was 3.1 to 26.6 GBq/μmol, and the radiochemical purity was > 99 %. In vivo studies in mice revealed lower uptake in the brains of α2A-KO mice compared to WT mice. The results for selectivity were confirmed by ex vivo brain autoradiography. Blocking studies revealed reduced uptake in α2A-adrenoceptor-rich brain regions in pretreated animals, demonstrating the specificity of the tracer. Metabolite analyses revealed very rapid metabolism of 6-[18F]fluoro-marsanidine with blood-brain barrier-permeable metabolites in both rats and mice. CONCLUSION 6-[18F]Fluoro-marsanidine was synthesized and evaluated as a PET tracer candidate for brain α2A-adrenoceptors. However, rapid metabolism, extensive presence of labeled metabolites in the brain, and high non-specific uptake in mouse and rat brain make 6-[18F]fluoro-marsanidine unsuitable for α2A-adrenoceptor targeting in rodents in vivo.
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Affiliation(s)
- Anna Krzyczmonik
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Thomas Keller
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Francisco R López-Picón
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Sarita Forsback
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,Department of Chemistry, University of Turku, Turku, Finland
| | - Anna K Kirjavainen
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland
| | - Jatta S Takkinen
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Aleksandra Wasilewska
- Department of Chemical Technology of Drugs, Faculty of Pharmacy, Medical University of Gdańsk, Gdańsk, Poland
| | - Mika Scheinin
- Institute of Biomedicine, University of Turku, and Unit of Clinical Pharmacology, Turku University Hospital, Turku, Finland
| | - Merja Haaparanta-Solin
- PET Preclinical Imaging Laboratory, Turku PET Centre, University of Turku, Turku, Finland.,MediCity Research Laboratory, University of Turku, Turku, Finland
| | - Franciszek Sączewski
- Department of Chemical Technology of Drugs, Faculty of Pharmacy, Medical University of Gdańsk, Gdańsk, Poland
| | - Olof Solin
- Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland. .,Department of Chemistry, University of Turku, Turku, Finland. .,Accelerator Laboratory, Turku PET Centre, Åbo Akademi University, Kiinamyllynkatu 4-8, FI-20520, Turku, Finland.
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6
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de Oliveira PG, Ramos MLS, Amaro AJ, Dias RA, Vieira SI. G i/o-Protein Coupled Receptors in the Aging Brain. Front Aging Neurosci 2019; 11:89. [PMID: 31105551 PMCID: PMC6492497 DOI: 10.3389/fnagi.2019.00089] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 04/03/2019] [Indexed: 12/18/2022] Open
Abstract
Cells translate extracellular signals to regulate processes such as differentiation, metabolism and proliferation, via transmembranar receptors. G protein-coupled receptors (GPCRs) belong to the largest family of transmembrane receptors, with over 800 members in the human species. Given the variety of key physiological functions regulated by GPCRs, these are main targets of existing drugs. During normal aging, alterations in the expression and activity of GPCRs have been observed. The central nervous system (CNS) is particularly affected by these alterations, which results in decreased brain functions, impaired neuroregeneration, and increased vulnerability to neuropathologies, such as Alzheimer's and Parkinson diseases. GPCRs signal via heterotrimeric G proteins, such as Go, the most abundant heterotrimeric G protein in CNS. We here review age-induced effects of GPCR signaling via the Gi/o subfamily at the CNS. During the aging process, a reduction in protein density is observed for almost half of the Gi/o-coupled GPCRs, particularly in age-vulnerable regions such as the frontal cortex, hippocampus, substantia nigra and striatum. Gi/o levels also tend to decrease with aging, particularly in regions such as the frontal cortex. Alterations in the expression and activity of GPCRs and coupled G proteins result from altered proteostasis, peroxidation of membranar lipids and age-associated neuronal degeneration and death, and have impact on aging hallmarks and age-related neuropathologies. Further, due to oligomerization of GPCRs at the membrane and their cooperative signaling, down-regulation of a specific Gi/o-coupled GPCR may affect signaling and drug targeting of other types/subtypes of GPCRs with which it dimerizes. Gi/o-coupled GPCRs receptorsomes are thus the focus of more effective therapeutic drugs aiming to prevent or revert the decline in brain functions and increased risk of neuropathologies at advanced ages.
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Affiliation(s)
- Patrícia G de Oliveira
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - Marta L S Ramos
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - António J Amaro
- School of Health Sciences (ESSUA), Universidade de Aveiro, Aveiro, Portugal
| | - Roberto A Dias
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
| | - Sandra I Vieira
- Department of Medical Sciences, Institute of Biomedicine (iBiMED) and The Discovery CTR, Universidade de Aveiro, Aveiro, Portugal
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Abstract
Presynaptic receptors are sites at which transmitters, locally formed mediators or hormones inhibit or facilitate the release of a given transmitter from its axon terminals. The interest in the identification of presynaptic receptors has faded in recent years and it may therefore be justified to give an overview of their occurrence in the autonomic and central nervous system; this review will focus on presynaptic receptors in human tissues. Autoreceptors are presynaptic receptors at which a given transmitter restrains its further release, though in some instances may also increase its release. Inhibitory autoreceptors represent a typical example of a negative feedback; they are tonically activated by the respective endogenous transmitter and/or are constitutively active. Autoreceptors also play a role under pathophysiological conditions, e.g. by limiting the massive noradrenaline release occurring during congestive heart failure. They can be used for therapeutic purposes; e.g., the α2-adrenoceptor antagonist mirtazapine is used as an antidepressant and the inverse histamine H3 receptor agonist pitolisant has been marketed as a new drug for the treatment of narcolepsy in 2016. Heteroreceptors are presynaptic receptors at which transmitters from adjacent neurons, locally formed mediators (e.g. endocannabinoids) or hormones (e.g. adrenaline) can inhibit or facilitate transmitter release; they may be subject to an endogenous tone. The constipating effect of the sympathetic nervous system or of the antihypertensive drug clonidine is related to the activation of inhibitory α2-adrenoceptors on postganglionic parasympathetic neurons. Part of the stimulating effect of adrenaline on the sympathetic nervous system during stress is related to its facilitatory effect on noradrenaline release via β2-adrenoceptors.
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Affiliation(s)
| | - Thomas Feuerstein
- Sektion Neuroelektronische Systeme, Klinik für Neurochirurgie, Universität Freiburg, Germany
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8
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Rivero G, Gabilondo AM, García-Sevilla JA, La Harpe R, Callado LF, Meana JJ. Increased α2- and β1-adrenoceptor densities in postmortem brain of subjects with depression: differential effect of antidepressant treatment. J Affect Disord 2015; 167:343-50. [PMID: 25020269 DOI: 10.1016/j.jad.2014.06.016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/09/2014] [Accepted: 06/10/2014] [Indexed: 11/19/2022]
Abstract
BACKGROUND Brain α2- and β-adrenoceptor alterations have been suggested in suicide and major depressive disorder. METHODS The densities of α2-, β1- and β2-adrenoceptors in postmortem prefrontal cortex of 26 subjects with depression were compared with those of age-, gender- and postmortem delay-matched controls. The effect of antidepressant treatment on α2- and β-adrenoceptor densities was also evaluated. α2- and β-adrenoceptor densities were measured by saturation experiments with respective radioligands [(3)H]UK14304 and [(3)H]CGP12177. β1- and β2-adrenoceptor subtype densities were dissected by means of β1-adrenoceptor selective antagonist CGP20712A. RESULTS Both, α2- and β1-adrenoceptors densities were higher in antidepressant-free depressed subjects (n=14) than those in matched controls (Δ~24%, p=0.013 and Δ~20%, p=0.044, respectively). In antidepressant-treated subjects (n=12), α2-adrenoceptor density remained increased over that in controls (Δ~20%), suggesting a resistance of α2-adrenoceptors to the down-regulatory effect of antidepressants. By contrast, β1-adrenoceptor density in antidepressant-treated depressed subjects was not different from controls, suggesting a possible down-regulation by antidepressants. The down-regulation of β1-adrenoceptor density in antidepressant-treated depressed subjects differs from the unaltered β1-adrenoceptor density observed in citalopram-treated rats and in a group of non-depressed subjects also treated with antidepressants (n=6). β2-adrenoceptor density was not altered in depressed subjects independently of treatment. LIMITATIONS Antidepressant-treated subjects had been treated with a heterogeneous variety of antidepressant drugs. The results should be understood in the context of suicide victims with depression. CONCLUSIONS These results show the up-regulation of brain α2- and β1-adrenoceptors in depression and suggest that the regulation induced by chronic antidepressant treatment would be altered in these subjects.
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MESH Headings
- Adult
- Animals
- Antidepressive Agents/pharmacology
- Antidepressive Agents/therapeutic use
- Depression/drug therapy
- Depression/pathology
- Depressive Disorder, Major/drug therapy
- Depressive Disorder, Major/pathology
- Female
- Humans
- Male
- Middle Aged
- Prefrontal Cortex/drug effects
- Prefrontal Cortex/pathology
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, alpha-2/analysis
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, beta-1/analysis
- Receptors, Adrenergic, beta-1/drug effects
- Reference Values
- Signal Transduction/drug effects
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Affiliation(s)
- Guadalupe Rivero
- Department of Pharmacology, University of the Basque Country (UPV/EHU), Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain.
| | - Ane M Gabilondo
- Department of Pharmacology, University of the Basque Country (UPV/EHU), Spain; BioCruces Health Research Institute, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain
| | - Jesús A García-Sevilla
- Laboratory of Neuropharmacology, Institut Universitari d'Investigació en Ciències de la Salut (IUNICS), University of the Balearic Islands, Spain
| | - Romano La Harpe
- Centre Universitaire Romand de Médicine Légale-site Genève, University of Geneva, Switzerland
| | - Luis F Callado
- Department of Pharmacology, University of the Basque Country (UPV/EHU), Spain; BioCruces Health Research Institute, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain
| | - J Javier Meana
- Department of Pharmacology, University of the Basque Country (UPV/EHU), Spain; BioCruces Health Research Institute, Spain; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Spain
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Fluorinated analogues of marsanidine, a highly α2-AR/imidazoline I1 binding site-selective hypotensive agent. Synthesis and biological activities. Eur J Med Chem 2014; 87:386-97. [PMID: 25282262 DOI: 10.1016/j.ejmech.2014.09.083] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 09/25/2014] [Accepted: 09/26/2014] [Indexed: 01/25/2023]
Abstract
The aim of these studies was to establish the influence of fluorination of the indazole ring on the pharmacological properties of two selective α2-adrenoceptor (α2-AR) agonists: 1-[(imidazolidin-2-yl)imino]-1H-indazole (marsanidine, A) and its methylene analogue 1-[(4,5-dihydro-1H-imidazol-2-yl)methyl]-1H-indazole (B). Introduction of fluorine into the indazole ring of A and B reduced both binding affinity and α2-AR/I1 imidazoline binding site selectivity. The most α2-AR-selective ligands were 6-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6c) and 7-fluoro-1-[(imidazolidin-2-yl)imino]-1H-indazole (6d). The in vivo cardiovascular properties of fluorinated derivatives of A and B revealed that in both cases the C-7 fluorination leads to compounds with the highest hypotensive and bradycardic activities. The α2-AR partial agonist 6c was prepared as a potential lead compound for development of a radiotracer for PET imaging of brain α2-ARs.
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Concentrations of platelet α2-adrenoceptors, lymphocyte muscarinic receptors, and blood monoamines in dogs (Canis familiaris) affected by canine cognitive dysfunction syndrome. J Vet Behav 2013. [DOI: 10.1016/j.jveb.2012.06.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Xu Y, Yan J, Zhou P, Li J, Gao H, Xia Y, Wang Q. Neurotransmitter receptors and cognitive dysfunction in Alzheimer's disease and Parkinson's disease. Prog Neurobiol 2012; 97:1-13. [PMID: 22387368 DOI: 10.1016/j.pneurobio.2012.02.002] [Citation(s) in RCA: 198] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 01/06/2012] [Accepted: 02/15/2012] [Indexed: 12/12/2022]
Abstract
Cognitive dysfunction is one of the most typical characteristics in various neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease (advanced stage). Although several mechanisms like neuronal apoptosis and inflammatory responses have been recognized to be involved in the pathogenesis of cognitive dysfunction in these diseases, recent studies on neurodegeneration and cognitive dysfunction have demonstrated a significant impact of receptor modulation on cognitive changes. The pathological alterations in various receptors appear to contribute to cognitive impairment and/or deterioration with correlation to diversified mechanisms. This article recapitulates the present understandings and concepts underlying the modulation of different receptors in human beings and various experimental models of Alzheimer's disease and Parkinson's disease as well as a conceptual update on the underlying mechanisms. Specific roles of serotonin, adrenaline, acetylcholine, dopamine receptors, and N-methyl-D-aspartate receptors in Alzheimer's disease and Parkinson's disease will be interactively discussed. Complex mechanisms involved in their signaling pathways in the cognitive dysfunction associated with the neurodegenerative diseases will also be addressed. Substantial evidence has suggested that those receptors are crucial neuroregulators contributing to cognitive pathology and complicated correlations exist between those receptors and the expression of cognitive capacities. The pathological alterations in the receptors would, therefore, contribute to cognitive impairments and/or deterioration in Alzheimer's disease and Parkinson's disease. Future research may shed light on new clues for the treatment of cognitive dysfunction in neurodegenerative diseases by targeting specific alterations in these receptors and their signal transduction pathways in the frontal-striatal, fronto-striato-thalamic, and mesolimbic circuitries.
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Affiliation(s)
- Yunqi Xu
- Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong 510630, PR China
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Jardanhazi-Kurutz D, Kummer MP, Terwel D, Vogel K, Thiele A, Heneka MT. Distinct adrenergic system changes and neuroinflammation in response to induced locus ceruleus degeneration in APP/PS1 transgenic mice. Neuroscience 2010; 176:396-407. [PMID: 21129451 DOI: 10.1016/j.neuroscience.2010.11.052] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 11/23/2010] [Accepted: 11/24/2010] [Indexed: 02/07/2023]
Abstract
Degeneration of locus ceruleus (LC) neurons and subsequent reduction of norepinephrine (NE) in LC projection areas represent an early pathological indicator of Alzheimer's disease (AD). In order to study the effects of NE depletion on cortical and hippocampal adrenergic system changes, LC degeneration was induced in 3-month-old APP/PS1 mice by the neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (dsp4). Dsp4 induced a widespread loss of norepinephrine transporter binding in multiple brain structures already at 4.5 months. This was accompanied by changes of α-1-, α-2-, and β-1-adreneroceptor binding sites as well as altered adrenoceptor mRNA expression. In parallel, we observed increased micro- and astrogliosis in cortical and hippocampal structures in dsp4-treated groups. In addition, the expression of the pro-inflammatory cytokines CCL2 and IL-1β were induced in both, dsp4-treated and APP/PS1-transgenic mice, whereas IL-1α was only up-regulated in dsp4-treated APP/PS1 mice. Concerning amyloid β (Aβ) deposition, we observed an elevation of Aβ1-42 levels in aged dsp4-treated APP/PS1 mice. These data support the hypothesis that LC degeneration leads to dysregulation of adrenergic receptors and exacerbation of Aβ-induced neuroinflammation, both of which are exploitable for early disease marker development.
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Affiliation(s)
- D Jardanhazi-Kurutz
- Global Drug Discovery, Bayer Schering Pharma AG, Berlin, Müllerstrasse 178, 13342 Berlin, Germany
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13
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Osella MC, Re G, Odore R, Girardi C, Badino P, Barbero R, Bergamasco L. Canine cognitive dysfunction syndrome: Prevalence, clinical signs and treatment with a neuroprotective nutraceutical. Appl Anim Behav Sci 2007. [DOI: 10.1016/j.applanim.2006.11.007] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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14
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Szot P, White SS, Greenup JL, Leverenz JB, Peskind ER, Raskind MA. Compensatory changes in the noradrenergic nervous system in the locus ceruleus and hippocampus of postmortem subjects with Alzheimer's disease and dementia with Lewy bodies. J Neurosci 2006; 26:467-78. [PMID: 16407544 PMCID: PMC6674412 DOI: 10.1523/jneurosci.4265-05.2006] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In Alzheimer's disease (AD), there is a significant loss of locus ceruleus (LC) noradrenergic neurons. However, functional and anatomical evidence indicates that the remaining noradrenergic neurons may be compensating for the loss. Because the noradrenergic system plays an important role in learning and memory, it is important to determine whether compensation occurs in noradrenergic neurons in the LC and hippocampus of subjects with AD or a related dementing disorder, dementia with Lewy bodies (DLB). We observed profound neuronal loss in the LC in AD and DLB subjects with three major changes in the noradrenergic system consistent with compensation: (1) an increase in tyrosine hydroxylase (TH) mRNA expression in the remaining neurons; (2) sprouting of dendrites into peri-LC dendritic zone, as determined by alpha2-adrenoreceptors (ARs) and norepinephrine transporter binding sites; and (3) sprouting of axonal projections to the hippocampus as determined by alpha2-ARs. In AD and DLB subjects, the postsynaptic alpha1-ARs were normal to elevated. Expression of alpha1A- and alpha2A-AR mRNA in the hippocampus of AD and DLB subjects were not altered, but expression of alpha1D- and alpha2C-AR mRNA was significantly reduced in the hippocampus of AD and DLB subjects. Therefore, in AD and DLB subjects, there is compensation occurring in the remaining noradrenergic neurons, but there does appear to be a loss of specific AR in the hippocampus. Because changes in these noradrenergic markers in AD versus DLB subjects were similar (except neuronal loss and the increase in TH mRNA were somewhat greater in DLB subjects), the presence of Lewy bodies in addition to plaques and tangles in DLB subjects does not appear to further affect the noradrenergic compensatory changes.
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MESH Headings
- Adrenergic alpha-Antagonists/metabolism
- Adult
- Aged
- Aged, 80 and over
- Alzheimer Disease/metabolism
- Alzheimer Disease/pathology
- Dendrites/ultrastructure
- Female
- Fluoxetine/analogs & derivatives
- Fluoxetine/metabolism
- Hippocampus/chemistry
- Hippocampus/pathology
- Humans
- Idazoxan/analogs & derivatives
- Idazoxan/metabolism
- In Situ Hybridization
- Lewy Body Disease/metabolism
- Lewy Body Disease/pathology
- Locus Coeruleus/chemistry
- Locus Coeruleus/pathology
- Male
- Middle Aged
- Nerve Tissue Proteins/analysis
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Norepinephrine/chemistry
- Norepinephrine/physiology
- Norepinephrine Plasma Membrane Transport Proteins/analysis
- Norepinephrine Plasma Membrane Transport Proteins/metabolism
- Prazosin/metabolism
- RNA, Messenger/analysis
- RNA, Messenger/biosynthesis
- Receptors, Adrenergic, alpha-1/analysis
- Receptors, Adrenergic, alpha-1/genetics
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-2/analysis
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Tetralones/metabolism
- Tyrosine 3-Monooxygenase/analysis
- Tyrosine 3-Monooxygenase/biosynthesis
- Tyrosine 3-Monooxygenase/genetics
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Affiliation(s)
- Patricia Szot
- Northwest Network for Mental Illness Research, Education, and Clinical Center, Veterans Administration Puget Sound Health Care System, Seattle, Washington 98108, USA.
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15
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SCHAMBRA UB, MACKENSEN GB, STAFFORD-SMITH M, HAINES DE, SCHWINN DA. Neuron specific alpha-adrenergic receptor expression in human cerebellum: implications for emerging cerebellar roles in neurologic disease. Neuroscience 2006; 135:507-23. [PMID: 16112482 PMCID: PMC2277099 DOI: 10.1016/j.neuroscience.2005.06.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 06/06/2005] [Accepted: 06/15/2005] [Indexed: 12/13/2022]
Abstract
Recent data suggest novel functional roles for cerebellar involvement in a number of neurologic diseases. Function of cerebellar neurons is known to be modulated by norepinephrine and adrenergic receptors. The distribution of adrenergic receptor subtypes has been described in experimental animals, but corroboration of such studies in the human cerebellum, necessary for drug treatment, is still lacking. In the present work we studied cell-specific localizations of alpha1 adrenergic receptor subtype mRNA (alpha 1a, alpha 1b, alpha 1d), and alpha2 adrenergic receptor subtype mRNA (alpha 2a, alpha 2b, alpha 2c) by in situ hybridization on cryostat sections of human cerebellum (cortical layers and dentate nucleus). We observed unique neuron-specific alpha1 adrenergic receptor and alpha2 adrenergic receptor subtype distribution in human cerebellum. The cerebellar cortex expresses mRNA encoding all six alpha adrenergic receptor subtypes, whereas dentate nucleus neurons express all subtype mRNAs, except alpha 2a adrenergic receptor mRNA. All Purkinje cells label strongly for alpha 2a and alpha 2b adrenergic receptor mRNA. Additionally, Purkinje cells of the anterior lobe vermis (lobules I to V) and uvula/tonsil (lobules IX/HIX) express alpha 1a and alpha 2c subtypes, and Purkinje cells in the ansiform lobule (lobule HVII) and uvula/tonsil express alpha 1b and alpha 2c adrenergic receptor subtypes. Basket cells show a strong signal for alpha 1a, moderate signal for alpha 2a and light label for alpha 2b adrenergic receptor mRNA. In stellate cells, besides a strong label of alpha 2a adrenergic receptor mRNA in all and moderate label of alpha 2b message in select stellate cells, the inner stellate cells are also moderately positive for alpha 1b adrenergic receptor mRNA. Granule and Golgi cells express high levels of alpha 2a and alpha 2b adrenergic receptor mRNAs. These data contribute new information regarding specific location of adrenergic receptor subtypes in human cerebellar neurons. We discuss our observations in terms of possible modulatory roles of adrenergic receptor subtypes in cerebellar neurons responding to sensory and autonomic input signals, and review species differences in cerebellar adrenergic receptor expression.
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Affiliation(s)
- U. B. SCHAMBRA
- Department of Anatomy and Cell Biology, Quillen College of Medicine, East Tennessee State University, Box 70582, Johnson City, TN 37614-0582, USA
- *Corresponding author. Tel: +1-423-439-2014; fax: +1-423-439-2017. E-mail address: (U. B. Schambra)
| | - G. B. MACKENSEN
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - M. STAFFORD-SMITH
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - D. E. HAINES
- Department of Anatomy, University of Mississippi Medical Center, Jackson, MS 39216, USA
| | - D. A. SCHWINN
- Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
- Department of Surgery, Duke University Medical Center, Durham, NC 27710, USA
- Department of Pharmacology/Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
- *Corresponding author. Tel: +1-423-439-2014; fax: +1-423-439-2017. E-mail address: (U. B. Schambra)
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Martín-Gómez JI, Ruiz J, Barrondo S, Callado LF, Meana JJ. Opposite changes in Imidazoline I2 receptors and α2-adrenoceptors density in rat frontal cortex after induced gliosis. Life Sci 2005; 78:205-9. [PMID: 16107261 DOI: 10.1016/j.lfs.2005.04.054] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Accepted: 04/18/2005] [Indexed: 11/29/2022]
Abstract
Opposite age-dependent changes in alpha2-adrenoceptor and imidazoline I2 receptor (I2-IRs) density have been related to brain gliosis development with aging. To check this hypothesis we applied in rats a model of reactive gliosis induced by heat. The specific binding of [3H]idazoxan (0.5-20 nM) in the presence of (-)adrenaline (5 x 10(-6) M) to membranes from rat brain cortex showed that the density of I(2)-IRs was significantly higher in membranes of injured cortex (Bmax=60+/-6 fmol/mg protein; n=9) than in control (Bmax=38+/-3 fmol/mg protein; n=9; p=0.0053). Conversely, the density of alpha2-adrenoceptors, measured by [3H]clonidine (0.25-16 nM), in the injured cortex (Bmax=75+/-4 fmol/mg protein; n=9) was significantly lower than in sham membranes (Bmax=103+/-7 fmol/mg protein; n=9; p=0.0035). No significant differences in receptor's affinity were observed between both groups. These results support the hypothesis that gliosis induces opposite changes in alpha2-adrenoceptor and I2-IR density.
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Affiliation(s)
- J Ignacio Martín-Gómez
- Department of Pharmacology, University of the Basque Country, E-48940 Leioa, Bizkaia and E-01006 Vitoria-Gasteiz, Spain
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17
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Schmitt HP. Neuro-modulation, aminergic neuro-disinhibition and neuro-degeneration. Draft of a comprehensive theory for Alzheimer disease. Med Hypotheses 2005; 65:1106-19. [PMID: 16125326 DOI: 10.1016/j.mehy.2005.06.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2005] [Revised: 06/22/2005] [Accepted: 06/23/2005] [Indexed: 12/18/2022]
Abstract
A comprehensive theory for Alzheimer disease (AD) which can provide a clue to the neuronal selective vulnerability (pathoklisis) is still missing. Based upon evidence from the current literature, the present work is aimed at proposing such a theory, namely the 'aminergic disinhibition theory' of AD. It includes data-based hypotheses as to the pathoklisis, mechanisms of neuro-degeneration and dementia as well as the aetiology of the disease. Alzheimer disease is regarded as a disorder of neural input modulation caused by the degeneration of four modulatory amine transmitter (MAT) systems, namely the serotoninergic, the noradrenergic, the histaminergic, and the cholinergic systems with ascending projections. MATs modulate cognitive processing including arousal, attention, and synaptic plasticity in learning and memory, not only through direct, mostly inhibitory impact on principal neurones but also partially through interaction with local networks of GABA-ergic inter-neurones. The distribution and magnitude of the pathology in AD roughly correlate with the distribution and magnitude of MAT modulation: Regions more densely innervated by ascending MAT projections are, as a rule, more severely affected than areas receiving less MAT innervation. Because the global effect of MATs in the forebrain is inhibition, the degeneration of four MAT systems, some related peptidergic systems and a secondary alleviation of the GABA-ergic transmission means a fundamental loss of inhibitory impact in the neuronal circuitry resulting in neuronal (aminergic) disinhibition. Clearly, the basic mechanism promoting neuronal death in AD is thought to be a chronic disturbance of the inhibition-excitation balance to the advantage of excitation. Chronic over-excitation is conceived to result in Ca2+ dependent cellular excito-toxicity leading to neuro-degeneration including amyloid-beta production and NFT formation. Disinhibited neurons will degenerate while less excited (relatively over-inhibited) neurones will survive. Because the decline of aminergic transmission in AD is likely to start at the receptor level, it is hypothesized that early impairment by a molecular 'hit' to an MAT receptor (or a group of receptors) initiates a pathogenetic cascade that develops in an avalanche-like manner. Based on experimental evidence from the literature, the 'hit' might be the attachment of a targeted pathogen like a small roaming amino acid sequence to the receptor(s), e.g., the serotoninergic 5-HT2A-R. Referential sequence analysis could be a means to identify such a small pathogen hidden in a large receptor molecule.
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Affiliation(s)
- H Peter Schmitt
- Institute of Pathology, Department for Neuropathology, University of Heidelberg, Im Neuernheimer Feld 220-221, 69120 Heidelberg, Germany.
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18
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Mato S, Pazos A. Influence of age, postmortem delay and freezing storage period on cannabinoid receptor density and functionality in human brain. Neuropharmacology 2004; 46:716-26. [PMID: 14996549 DOI: 10.1016/j.neuropharm.2003.11.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2003] [Revised: 10/08/2003] [Accepted: 10/31/2003] [Indexed: 11/23/2022]
Abstract
It has been suggested that cannabimimetic drugs could be of interest in the treatment of several nervous disorders. Thus, it is important to analyse the distribution and properties of cannabinoid (CB) receptors directly in human brain. As postmortem human tissue is subjected to the effects of several biological variables, we have analyzed by autoradiography the influence of age, postmortem delay and freezing storage period (at -25 degrees C) on two parameters corresponding to cannabinoid CB1 receptors in human frontal cortex: receptor density and degree of activation of G-proteins ([35S]GTPgammaS assays). A significant decrease in the amount of both receptor density and agonist-stimulated G-protein activity was observed with age, revealing a mean reduction of about 10% per decade. In contrast, no significant correlations were found with postmortem delay either for CB1 receptors density or functionality. Finally, both parameters (receptor density and [35S]GTPgammaS response) were significantly reduced with freezing storage period at -25 degrees C in frontal cortical layers. Non-linear analysis of these data yielded values between 12 and 24 months of storage for a 50% reduction. In conclusion, when studying CB1 receptor properties in human brain samples, a careful analysis (and matching) for variables such as age and freezing storage period has to be carried out.
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Affiliation(s)
- S Mato
- Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, Avda Herera Oria s/n, 39011 Santander, Spain
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19
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Matthews KL, Chen CPLH, Esiri MM, Keene J, Minger SL, Francis PT. Noradrenergic changes, aggressive behavior, and cognition in patients with dementia. Biol Psychiatry 2002; 51:407-16. [PMID: 11904135 DOI: 10.1016/s0006-3223(01)01235-5] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND We wished to examine the integrity of the noradrenergic system in patients with Alzheimer's disease, mixed/other dementias and controls, and possible relationships between changes in the noradrenergic system and the presence of behavioral and psychiatric signs and symptoms in dementia. METHODS Alpha(2) adrenoceptor sites were measured by radioligand binding in three cortical regions of 46 individuals with dementia and 33 elderly normal controls together with cortical noradrenaline concentration and locus coeruleus cell and neurofibrillary tangle counts. RESULTS The alpha(2) adrenergic receptor density was unaltered in patients with Alzheimer's disease, mixed/other dementias compared with controls; however, there was a loss of locus coeruleus cells in subjects with dementia, reaching 50% within the rostral nucleus. In addition, a significant reduction was seen in the midtemporal cortical noradrenaline concentration (31% decrease) in patients with Alzheimer's disease. In subjects with dementia, there was a positive correlation between aggressive behavior and magnitude of rostral locus coeruleus cell loss, while the reduction in noradrenaline concentration correlated with cognitive impairment. CONCLUSIONS Subgroups of patients with Alzheimer's disease may have different neurochemical changes from patients lacking these changes. Therefore, this study may have implications for the treatment of behavioral and psychiatric signs and symptoms in dementia, particularly aggressive behavior in patients with dementia.
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Affiliation(s)
- Kim L Matthews
- Dementia Research Laboratory, Centre for Neuroscience Research, GKT School of Biomedical Sciences, King's College, London, UK
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20
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Granholm AC, Helt C, Srivastava N, Backman C, Gerhardt GA. Effects of age and GDNF on noradrenergic innervation of the hippocampal formation: studies from intraocular grafts. Microsc Res Tech 2001; 54:298-308. [PMID: 11514986 DOI: 10.1002/jemt.1142] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Recent studies have suggested that factors in the target tissue influence the degree of plasticity and regeneration following aging and/or specific insults. We have investigated whether young or aged targets differ in their noradrenergic innervation from fetal locus coeruleus (LC) neurons, and also if a specific growth factor, glial cell line-derived neurotrophic factor (GDNF) can affect this innervation pattern. Tissue pieces of fetal brainstem and young (3 months) or old (18 months) iris tissue were transplanted simultaneously into the anterior chamber of the eye of adult hosts. We found that aged iris transplants became innervated to a significantly lesser degree by the cografted LC neurons than young iris transplants. Fetal hippocampal tissue was then grafted to adult hosts, and a fetal brainstem graft containing LC neurons was placed adjacent to the first graft, either at 3 or 21 months post-grafting. Thus, old/young chimeras of the noradrenergic coeruleo-hippocampal pathway were created. Aged hippocampal grafts received a much less dense innervation from co-grafted LC neurons than young hippocampal grafts. Tyrosine hydroxylase-positive-immunoreactive innervation was only found in the outskirts of aged grafts, while the young hippocampal grafts contained an even innervation pattern. The innervation density of hippocampal grafts was significantly enhanced by GDNF treatment. These findings demonstrate that target-derived factors may regulate neuronal plasticity, and that the age of the target is more important for innervation properties than the age of the neuron innervating a particular target.
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Affiliation(s)
- A C Granholm
- Department of Physiology and Neuroscience, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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21
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Leverenz JB, Miller MA, Dobie DJ, Peskind ER, Raskind MA. Increased alpha 2-adrenergic receptor binding in locus coeruleus projection areas in dementia with Lewy bodies. Neurobiol Aging 2001; 22:555-61. [PMID: 11445255 DOI: 10.1016/s0197-4580(01)00221-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Clinical studies suggest involvement of brain noradrenergic systems in the pathophysiology of disruptive agitation in Alzheimer's disease (AD). This behavioral problem is even more prevalent in dementia with Lewy bodies (DLB). Here we used receptor autoradiography with [(125)I]para-iodoclonidine to estimate alpha-2 adrenergic receptor (A2R) density in locus coeruleus (LC) projection areas in postmortem brain tissue from age and gender comparable groups of DLB (n = 6), AD (n = 5) and normal (n = 7) subjects. LC neuronal loss was substantial and equivalent in DLB and AD. A2R density was greater in DLB than in normals in the deep layers of the frontal cortex. A2R density was greater in DLB than in AD in hippocampus (CA-1, CA-3 and dentate hilus) and in the granule layer of the cerebellum. Increased A2R binding in DLB is consistent with expression of presynaptic A2R on fibers from surviving LC neurons involved in reinnervation of LC projection areas. These areas develop compensatory noradrenergic hyperinnervation in a rat model of partial LC ablation. It is also consistent with upregulation of post-synaptic A2R in response to loss of LC noradrenergic innervation. Either mechanism could lower the threshold for increased agitation in response to noradrenergic outflow in these dementing disorders.
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Affiliation(s)
- J B Leverenz
- Northwest Network Mental Illness Research, Education and Clinical Center (MIRECC), VA Puget Sound Health Care System, Seattle, WA 98108, USA.
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22
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González-Maeso J, Rodríguez-Puertas R, Gabilondo AM, Meana JJ. Characterization of receptor-mediated [35S]GTPgammaS binding to cortical membranes from postmortem human brain. Eur J Pharmacol 2000; 390:25-36. [PMID: 10708703 DOI: 10.1016/s0014-2999(99)00827-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The [35S]GTPgammaS binding assay represents a functional approach to assess the coupling between receptors and G-proteins. The optimal conditions for [35S]GTPgammaS binding to human brain homogenates were established in postmortem samples of prefrontal cortex. The influence of protein content, incubation time, GDP, Mg(2+), and NaCl concentrations on the [35S]GTPgammaS binding were assessed in the absence and presence of the alpha(2)-adrenoceptor agonist UK14304 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine). In conditions of 50 microM GDP and 100 mM NaCl, UK14304 increased the apparent affinity of the specific [35S]GTPgammaS binding without changing the apparent density. Concentration-response curves to agonists of alpha(2)-adrenoceptors, mu-opioid, 5-HT(1A), cholinergic muscarinic, and GABA(B) receptors displayed, in the presence of NaCl, maximal stimulations between 24% and 61% with EC(50) values in the micromolar range. Selective antagonists shifted to the right the agonist-induced stimulation curves. The G(i)/G(o)-protein alkylating agent N-ethylmaleimide decreased basal [35S]GTPgammaS binding in a concentration-dependent manner and inhibited the stimulation induced by the different agonists. In cortical sections, [35S]GTPgammaS binding to gray matter was stimulated by the agonist UK14304. The present study demonstrates that functional studies of the receptor coupling to G(i)/G(o)-proteins can be performed in postmortem human brain samples.
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Affiliation(s)
- J González-Maeso
- Departamento de Farmacología, Universidad del País Vasco/Euskal Herriko Unibertsitatea, E-48940 Leioa, Bizkaia, Spain
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Shiue C, Pleus RC, Shiue GG, Rysavy JA, Sunderland JJ, Cornish KG, Young SD, Bylund DB. Synthesis and biological evaluation of [11C]MK-912 as an alpha2-adrenergic receptor radioligand for PET studies. Nucl Med Biol 1998; 25:127-33. [PMID: 9468027 DOI: 10.1016/s0969-8051(97)00167-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In vitro studies showed that MK-912 ((2S, 12bS)1',3'-dimethylspiro(1,3,4,5',6,6',7,12b-octahydro -2H-benzo[b]furo[2,3-a]quinolizine)-2,4'-pyrimidin-2'-one) is a potent alpha2-adrenergic receptor antagonist with high affinity (Ki = 0.42, 0.26 and 0.03 nM to alpha2A, alpha2B and alpha2C, respectively) and high selectivity (alpha2A/alpha1A = 240; alpha2A/D-1 = 3600; alpha2A/D-2 = 3500; alpha2A/5-HT1 = 700; alpha2A/5-HT2 = 4100). The compound was labeled with 11C and evaluated in rodents and monkey as a specific radioligand for studying alpha2-adrenergic receptors using PET. [11C]MK-912 was synthesized by methylation of its desmethyl precursor, L-668,929, with [11C]CH3I in (Bu3O)P=O at 85 degrees C for 8 min followed by purification with HPLC in 18% yield in a synthesis time of 45 min from end of bombardment (EOB). The specific activity was 0.83-0.93 Ci/micromol and the radiochemical purity was 97%. The initial uptake of [11C]MK-912 in mouse brain, heart, lung, liver and kidney was high (5%, 4%, 5%, 17% and 8% per gram of organ, respectively, at 5 min postinjection) and the activities were then slowly cleared from these organs. The uptake of [11C]MK-912 in rat olfactory tubercle, a brain region with high density of alpha2-adrenergic receptors, was reduced by 30%, and the ratio of radioactivity in olfactory tubercle/cerebellum was reduced from 2:1 to 1:1 by coinjection of [11C]MK-912 with a potent alpha2-adrenergic receptor antagonist, atipamezole (3 mg/kg), indicating that compound 2 binds to alpha2-adrenergic receptors. However, a PET study in a rhesus monkey revealed that the initial influx of [11C]MK-912 into various brain regions (cerebellum, cortex, olfactory tubercle and striatum) was high (0.02%/cc), and the radioactivity was then washed out slowly and without significantly differential retention in these brain regions. This, coupled with the fact that none of the high-density alpha2-adrenergic receptor brain regions exceeds a few millimeters in diameter, suggests that [11C]MK-912 is probably not an ideal radioligand for studying alpha2-adrenergic receptors in humans using commercially available PET.
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Affiliation(s)
- C Shiue
- Center for Metabolic Imaging, Creighton University, Omaha, NE, USA
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24
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Adrenergic receptors in Alzheimer's disease brain: selective increases in the cerebella of aggressive patients. J Neurosci 1997. [PMID: 9204938 DOI: 10.1523/jneurosci.17-14-05573.1997] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In this study, the distribution and concentration of beta1, beta2, and alpha2 adrenergic receptors were examined in the frontal cortex, hypothalamus, and cerebellum of Alzheimer's disease (AD) and age-matched control human brains by receptor autoradiography. The purpose of this study was to detect changes in adrenergic receptor concentrations in key areas of the brain known to affect behavior. For these studies, [125I]iodopindolol ([125I]IPIN) was used to visualize total beta adrenergic sites (with ICI-89,406 and ICI-118, 551 as subtype-selective antagonists to visualize beta2 and beta1 receptors, respectively). [3H]UK-14,304 was used to localize the alpha2 sites. Essentially no significant difference in adrenergic receptor concentration was found between total AD cases taken together and control patients. It was found, however, that there were important distinctions within the AD group when cases were subdivided according to the presence or absence of aggression, agitation, and disruptive behavior. Aggressive AD patients had markedly increased (by approximately 70%) concentrations of alpha2 receptors in the cerebellar cortex compared with nonaggressive patients with similar levels of cognitive deficit. The levels of cerebellar alpha2 receptors in aggressive AD patients were slightly above the healthy elderly controls, suggesting that these receptors are preserved and perhaps increased in this subgroup of AD. beta1 And beta2 adrenergic receptors of the cerebellar cortex showed smaller but significant ( approximately 25%) increases in concentration in aggressive AD subjects versus both nonaggressive AD patients and controls. No significant differences were found in adrenergic receptor concentrations within the frontal cortex or hypothalamus. These results point out the importance of distinguishing behavioral subgroups of AD when looking for specific neurochemical changes. These autoradiographic results may reflect the importance of the cerebellum in behavioral control.
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25
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Ignatowski TA, Gallant S, Spengler RN. Temporal regulation by adrenergic receptor stimulation of macrophage (M phi)-derived tumor necrosis factor (TNF) production post-LPS challenge. J Neuroimmunol 1996; 65:107-17. [PMID: 8964892 DOI: 10.1016/0165-5728(96)00004-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Macrophage (M phi) responsiveness can be regulated by various mediators, including those which emanate from, and mimic, the sympathetic nervous system. Whereas beta-adrenergic agonists suppress, alpha 2-adrenergic agonists augment lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) production and gene expressed. The susceptibility of M phi s to regulation of LPS-induced TNF production and mRNA accumulation was examined following beta-adrenergic and alpha 2-adrenergic receptor activation at specific time points post-LPS challenge. Complete Freund's adjuvant-elicited murine M phi s were incubated with LPS (30 ng/ml) in the presence or absence of adrenergic agonists or antagonists. We assessed the susceptibility of immunologically-activated M phi s to adrenergic receptor regulation: a) during the 1 h delay in the production of TNF after LPS-stimulation, and b) during the rapid increase in TNF production which follows. Disparate responsiveness of M phi s to adrenergic drugs was observed during this time course of TNF production and TNF mRNA accumulation. In particular, while the concomitant addition of an alpha 2-adrenergic antagonist and LPS resulted in 45% suppression of TNF production, this selective blockade of alpha 2-adrenergic receptors on M phi s was equally effective throughout the first 45 min post-LPS challenge. After this initial period, the alpha 2-adrenergic receptor became progressively less responsive as demonstrated by the delayed addition of yohimbine (10(-5) M) post-LPS challenge. The addition of the selective alpha 2-adrenergic agonist UK-14304 (10(-7) M) to LPS-activated M phi s augmented TNF mRNA accumulation. However, this augmentation was even greater when the addition of the alpha 2-adrenergic agonist was delayed post-LPS challenge. It was also shown that the beta-adrenergic agonist isoproterenol (10(-6) M) produced maximum suppression of TNF production within the first 1.5 h post-LPS challenge. Suppression by isoproterenol (10(-6) M) of TNF mRNA accumulation occurred throughout the 2-h period assessed post-LPS stimulation of M phi s. The decline in isoproterenol-induced regulation was accompanied by an elevation in beta 2-adrenergic receptor mRNA accumulation. Furthermore, suppression of TNF production induced by a maximum concentration of isoproterenol was observed at various LPS concentrations (0.001-1000 ng/ml), although this was not as pronounced a suppression as demonstrated for dibutyrl cAMP. These results demonstrate that the susceptibility of M phi s to adrenergic receptor regulation changes throughout the time period necessary for gene activation and ultimate release of TNF. Thus, the production of TNF during LPS-dependent disease states may be regulated by adrenergic mediators throughout different temporal windows, better explaining the role played by the nervous system.
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Affiliation(s)
- T A Ignatowski
- Dept. of Pathology, S.U.N.Y. at Buffalo, School of Medicine and Biomedical Sciences 14214, USA
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Gsell W, Strein I, Riederer P. The neurochemistry of Alzheimer type, vascular type and mixed type dementias compared. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1996; 47:73-101. [PMID: 8841958 DOI: 10.1007/978-3-7091-6892-9_5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We present the results of a meta-analysis of neurochemical changes in human post mortem brains of Alzheimer type (AD), vascular type (VD) and mixed type (MF) dementias, and matched controls based on 275 articles published between January 1980 and February 1994. Severity of degeneration between the different neurochemical systems is as follows, although ranking is difficult with regard to limited numbers of investigations in some neurochemical systems: Cholinergic system > serotonergic system > excitatory amino acids > GABAergic system > energy metabolism > NA > oxidative stress parameters > neuropeptides > DA. But, within a neurochemical system, degeneration is not evenly distributed. Spared parameters, e.g. muscarinic receptors and MAO-B, allow to make some suggestions for future therapeutic strategies.
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Affiliation(s)
- W Gsell
- Department of Psychiatry, University of Würzburg, Federal Republic of Germany
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Sramek JJ, Viereck C, Huff FJ, Wardle T, Hourani J, Stewart JA, Cutler NR. A "bridging" (safety/tolerance) study of besipirdine hydrochloride in patients with Alzheimer's disease. Life Sci 1995; 57:1241-8. [PMID: 7674813 DOI: 10.1016/0024-3205(95)02068-t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Besipirdine hydrochloride is a novel compound with cholinergic and adrenergic activity being investigated as a treatment for Alzheimer's disease (AD). The pharmacodynamics of some anti-dementia drugs are known to differ in patients with AD as compared with elderly normals. The present study was designed to determine the maximum tolerated dose (MTD) of multiple oral doses of besipirdine in AD patients. Twelve AD patients (NINCDS/ADRDA criteria; 7M, 5F, ages 58-75, mean age 65) were randomized to besipirdine (n = 9) or placebo (n = 3) in a double-blind, parallel-group, rising-dose design. Doses were 10, 20, 30, and 40 mg bid for 2 days each, followed by 50 and 60 mg bid for 5 days each. The most common adverse events were asymptomatic postural hypotension and asymptomatic bradycardia. Two patients on active drug developed severe adverse events: 1 after 3 days at 50 mg bid (nausea and vomiting); 1 after 3 days at 60 mg bid (angina). Due to the anginal episode, the study was terminated on Day 17. Plasma concentrations increased linearly with dose for besipirdine and its major metabolite. The two patients who developed severe adverse events had the highest plasma concentrations measured. Besipirdine 50 mg bid was considered the maximum tolerated dose (MTD).
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Affiliation(s)
- J J Sramek
- California Clinical Trials, Beverly Hills 90211, USA
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García-Sevilla J, Miralles A, Sastre M, Escribá PV, Olmos G, Meana JJ. I2-imidazoline receptors in the healthy and pathologic human brain. Ann N Y Acad Sci 1995; 763:178-93. [PMID: 7677330 DOI: 10.1111/j.1749-6632.1995.tb32406.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- J García-Sevilla
- Department of Fundamental Biology and Health Sciences, University of the Balearic Islands, Palma de Mallorca, Spain
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Pascual J, Figols J, Grijalba B, González AM, del Olmo E, Berciano J, Pazos A. Changes in aminergic receptors in a PSP postmortem brain: correlation with pathological findings. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1994; 42:247-60. [PMID: 7964690 DOI: 10.1007/978-3-7091-6641-3_19] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The state of different aminergic receptors was assessed, by quantitative autoradiography in tissue sections, in several representative brain regions from a typical progressive supranuclear palsy (PSP) patient and from 9 matched brains. The densities of muscarinic receptors were within control limits in most of the brain areas of this PSP brain. Serotonin1 receptors were clearly reduced only in areas with very relevant neuropathological damage, such as locus niger and globus pallidus. The density of D1 dopamine receptors in the caudate-putamen and frontal cortex of the patient was within control limits. By contrast, nigral D1 and striatal D2 dopamine receptors were dramatically reduced in the patient as compared to controls. Finally, alpha 2-adrenoceptors were clearly reduced in all the examined areas of this PSP patient as compared to control group. Both the potential role of these receptor changes in the pathophysiology of the clinical features of PSP and their correlation with the neuropathological findings of this PSP patient are discussed.
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Affiliation(s)
- J Pascual
- Department of Physiology and Pharmacology, University Hospital Marqués de Valdecilla, University of Cantabria, Santander, Spain
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30
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Ruiz J, Martín I, Callado LF, Meana JJ, Barturen F, García-Sevilla JA. Non-adrenoceptor [3H]idazoxan binding sites (I2-imidazoline sites) are increased in postmortem brain from patients with Alzheimer's disease. Neurosci Lett 1993; 160:109-12. [PMID: 7902542 DOI: 10.1016/0304-3940(93)90925-b] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The I2-imidazoline site (a non-adrenergic mitochondrial site for which a glial location has been proposed and that is associated with the B-form of the enzyme monoamine oxidase) was evaluated in postmortem cortical membranes from 9 subjects with Alzheimer's disease (AD) and 9 matched-controls by using [3H]idazoxan (0.6-30 nM) in the presence of 10(-6) M (-)-adrenaline to prevent binding to alpha 2-adrenoceptors. In AD the density (Bmax) of I2-imidazoline sites was significantly higher (+63%) than in controls whereas no differences were apparent in affinity values (Kd). The results support the hypothesis that the I2 imidazoline site has a major location on glial (astrocyte) cells.
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Affiliation(s)
- J Ruiz
- Department of Pharmacology, University of the Basque Country, Leioa, Spain
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31
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Sastre M, García-Sevilla JA. Opposite age-dependent changes of alpha 2A-adrenoceptors and nonadrenoceptor [3H]idazoxan binding sites (I2-imidazoline sites) in the human brain: strong correlation of I2 with monoamine oxidase-B sites. J Neurochem 1993; 61:881-9. [PMID: 8395564 DOI: 10.1111/j.1471-4159.1993.tb03599.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In the postmortem human brain (27 specimens of frontal cortex, Brodmann area 9), the specific binding of the antagonists [3H]RX 821002 (2-methoxyidazoxan) to alpha 2A-adrenoceptors and that of [3H]idazoxan to I2-imidazoline sites (a nonadrenoceptor mitochondrial site) were determined in parallel to study the effect of aging (range, 4-89 years) on both brain proteins. The density of alpha 2A-adrenoceptors and age were negatively correlated (r = -0.71; p < 0.001). In contrast, the density of I2-imidazoline sites was positively correlated with aging (r = 0.59; p < 0.005). The ratio of receptor densities (alpha 2A/I2) also showed a marked negative correlation with age (r = -0.76; p < 0.001). In an age-selected group (range, 10-89 years), the density of monoamine oxidase (MAO)-B sites labeled by [3H]Ro 19-6327 (lazabemide) also showed a positive correlation with age (r = 0.80; p < 0.005). In these subjects, the density of I2-imidazoline sites correlated well with the density of MAO-B sites (r = 0.70; p < 0.005). The ratio of the density of these sites (MAO-B/I2) did not correlate with the age of the subject at death (r = -0.15). In the human frontal cortex, idazoxan displayed very low affinity (Ki = 89 microM) against the binding of [3H]Ro 19-6327 to MAO-B, which discounted a direct interaction of [3H]idazoxan with the active center of the enzyme and indicated that the I2-imidazoline site cannot be identified with MAO-B.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Sastre
- Department of Fundamental Biology and Health Sciences, University of the Balearic Islands, Palma de Mallorca, Spain
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Jorm CM, Stamford JA. Early age-dependent changes in noradrenaline efflux in the bed nucleus of stria terminalis: voltammetric data in rat brain slices. Neurobiol Aging 1993; 14:499-501. [PMID: 8247232 DOI: 10.1016/0197-4580(93)90108-n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Fast cyclic voltammetry (FCV) was applied to the detection of stimulated noradrenaline (NA) efflux in the bed nucleus of stria terminalis (BSTV) of the superfused rat brain slice from rats of different ages. Three age groups were compared: young (5 weeks; 130 +/- 8 g), adult (12 weeks; 308 +/- 12 g), and mature rats (36 weeks; 575 +/- 21 g). The effect of train duration (20-99 pulses at 100 Hz) and frequency of stimulation (50 pulses at 10-500 Hz) on NA efflux were examined. The effect of the alpha 2 antagonist yohimbine (1 microM) was also investigated. NA efflux was significantly (p < 0.05) greater in young than adult or mature rats on all train durations and stimulus frequencies tested: Maximal NA efflux on the longest train (99 pulses, 100 Hz, 10 mA, 0.2 ms) was 423 +/- 48 nM (young), 135 +/- 24 nM (adult), and 155 +/- 26 nM (mature). There were no significant differences between adult and mature rats. Yohimbine (1 microM) elevated NA efflux to a greater extent at lower (10 & 20 Hz) than higher frequencies in all age groups. Yohimbine also potentiated NA efflux more (p < 0.05) in young and adult rats than in mature animals. There were no significant differences between young and adult rats. The results indicate early maturational differences in both NA efflux and its control by alpha 2 adrenoceptors. Interestingly, the decreases in NA efflux and in yohimbine response were not temporally linked.
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Affiliation(s)
- C M Jorm
- Anaesthetics Unit, London Hospital Medical College, Royal London Hospital, Whitechapel, United Kingdom
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Abstract
To characterize further the alpha 2-adrenoceptor subtypes in terms of their regulation, monolayers of cells expressing either the alpha 2A (CHO-A2AR cells) or alpha 2C (OK cells) subtype were preincubated with norepinephrine for various times and the extent of receptor down-regulation was assessed. Exposure to 30 microM norepinephrine caused a similar time course and extent of down-regulation (approximately 50%) in both cells lines. The extent of down-regulation caused by 0.3 microM norepinephrine in OK cells was similar to that with 30 microM norepinephrine in CHO-A2AR cells, although the time course was somewhat slower. Reversal of the down-regulation of the alpha 2-adrenoceptor caused by 30 microM norepinephrine was more rapid in the CHO-A2AR than in the OK cell. With 0.3 microM norepinephrine, reversal of down-regulation of the alpha 2-adrenoceptor in the OK cell was slightly faster than that of the CHO-A2AR cell with 30 microM norepinephrine. These data indicate that although norepinephrine is more potent in causing down-regulation of the alpha 2C (OK cells) as compared to the alpha 2A subtype (CHO-A2AR cells), the time courses for down-regulation and its reversal are similar for the two subtypes.
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Affiliation(s)
- R C Pleus
- Department of Pharmacology, University of Nebraska Medical Center, Omaha 68198-6260
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