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Tian L, Liu X, Mei X, Cui R, Li X. The role of dopamine D1- and D2-like receptors related to muscarinic M1 receptors in impulsive choice in high-impulsive and low-impulsive rats. Pharmacol Biochem Behav 2019; 176:43-52. [DOI: 10.1016/j.pbb.2018.11.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 10/10/2018] [Accepted: 11/12/2018] [Indexed: 12/31/2022]
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2
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Yohn SE, Conn PJ. Positive allosteric modulation of M 1 and M 4 muscarinic receptors as potential therapeutic treatments for schizophrenia. Neuropharmacology 2018; 136:438-448. [PMID: 28893562 PMCID: PMC5844786 DOI: 10.1016/j.neuropharm.2017.09.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Revised: 09/06/2017] [Accepted: 09/08/2017] [Indexed: 01/22/2023]
Abstract
Current antipsychotic drugs provide symptomatic relief for positive symptoms of schizophrenia, but do not offer symptom management for negative and cognitive symptoms. In addition, many patients discontinue treatment due to adverse side effects. Therefore, there is a critical need to develop more effective and safe treatment options. Although the etiology of schizophrenia is unclear, considerable data from post-mortem, neuroimaging and neuropharmacology studies support a role of the muscarinic acetylcholine (mAChRs) in the pathophysiology of schizophrenia. Substantial evidence suggests that activation of mAChRs has the potential to treat all symptom domains of schizophrenia. Despite encouraging results in demonstrating efficacy, clinical trials of nonselective mAChR agonists were limited in their clinical utility due to dose-limiting peripheral side effects. Accordingly, efforts have been made to specifically target centrally located M1 and M4 mAChR subtypes devoid of adverse-effect liability. To circumvent this limitation, there have been tremendous advances in the discovery of ligands that bind at allosteric sites, binding sites distinct from the orthosteric site, which are structurally less conserved and thereby afford high levels of receptor subtype selectivity. The discovery of subtype-specific allosteric modulators has greatly advanced our understanding of the physiological role of various muscarinic receptor subtypes in schizophrenia and the potential utility of M1 and M4 mAChR subtypes as targets for the development of novel treatments for schizophrenia and related disorders. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.
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Affiliation(s)
- Samantha E Yohn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, United States
| | - P Jeffrey Conn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, TN 37232, United States.
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3
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Miyauchi M, Neugebauer NM, Sato T, Ardehali H, Meltzer HY. Muscarinic receptor signaling contributes to atypical antipsychotic drug reversal of the phencyclidine-induced deficit in novel object recognition in rats. J Psychopharmacol 2017; 31:1588-1604. [PMID: 28946779 DOI: 10.1177/0269881117731278] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Enhancement of cholinergic function via muscarinic acetylcholine receptor M1 agonism improves cognition in some schizophrenia patients. Most atypical antipsychotic drugs, including clozapine and its active metabolite, N-desmethylclozapine, and lurasidone, enhance the release of acetylcholine in key brain regions involved in cognition (e.g. hippocampus). We determined the effect of muscarinic acetylcholine receptor M1 stimulation on novel object recognition and its contribution to the ability of atypical antipsychotic drugs to reverse the novel object recognition deficit in rats withdrawn from subchronic phencyclidine, a rodent model of cognitive impairment in schizophrenia. In control rats, the non-specific muscarinic acetylcholine receptor antagonist, scopolamine, and the M1 selective antagonist, VU0255035, induced a novel object recognition deficit, which was reversed by the M1 agonist, AC260584. Scopolamine fully blocked the effect of clozapine and N-desmethylclozapine, but not lurasidone, to restore novel object recognition in subchronic phencyclidine-treated rats. VU0255035 also blocked these effects of clozapine and N-desmethylclozapine, but not lurasidone; however, the blockade was not as complete as that achieved with scopolamine. Furthermore, subchronic phencyclidine increased hippocampal M1 mRNA expression. These data suggest that M1 agonism is required for clozapine and N-desmethylclozapine to ameliorate the phencyclidine-induced deficit in novel object recognition, additional evidence that M1 agonism is a potential target for treating cognitive impairment in schizophrenia.
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Affiliation(s)
- Masanori Miyauchi
- 1 Department of Psychiatry and Behavioral Sciences, Northwestern Feinberg School of Medicine, Chicago, USA.,2 Sumitomo Dainippon Pharma Co., Ltd, Suita, Japan
| | - Nichole M Neugebauer
- 1 Department of Psychiatry and Behavioral Sciences, Northwestern Feinberg School of Medicine, Chicago, USA
| | - Tatsuya Sato
- 3 Feinberg Cardiovascular Research Institute (FCVRI), Northwestern University Feinberg School of Medicine, Chicago, USA
| | - Hossein Ardehali
- 3 Feinberg Cardiovascular Research Institute (FCVRI), Northwestern University Feinberg School of Medicine, Chicago, USA
| | - Herbert Y Meltzer
- 1 Department of Psychiatry and Behavioral Sciences, Northwestern Feinberg School of Medicine, Chicago, USA
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Wood MW, Martino G, Coupal M, Lindberg M, Schroeder P, Santhakumar V, Valiquette M, Sandin J, Widzowski D, Laird J. Broad analgesic activity of a novel, selective M1 agonist. Neuropharmacology 2017. [PMID: 28623171 DOI: 10.1016/j.neuropharm.2017.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although the muscarinic receptor family has long been a source of potentially compelling targets for small molecule drug discovery, it was difficult to achieve agonist selectivity within the family. A new class of M1 muscarinic agonists has emerged, and these compounds have been characterized as agonists that activate the receptor at an allosteric site. Members of this class of M1 agonists have been shown to be selective across the muscarinic receptors. However, upon introduction of a novel pharmacologic mechanism, it is prudent to ensure that no new off-target activities have arisen, particularly within the context of in vivo experiments. Reported here, is the in vitro and in vivo characterization of a novel M1 agonist tool compound, PPBI, and demonstrations that the primary biological effects of PPBI are mediated through M1. PPBI reverses d-amphetamine locomotor activity, but fails to do so in transgenic mice that do not express M1. PPBI also reverses a natural deficit in a rat cognition model at a level of exposure which also activates cortical circuitry. Most notably, PPBI is analgesic in a variety of rat and mouse models and the analgesic effect of PPBI is reversed by an M1-preferring antagonist and an M1-selective toxin. Finally, the pharmacokinetic/pharmacodynamic measures of PPBI are compared across multiple endpoints which highlights that activity in models of psychosis and pain require higher exposures than that required in the cognition model.
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Affiliation(s)
- Michael W Wood
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States.
| | - Giovanni Martino
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Martin Coupal
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Mattias Lindberg
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Patricia Schroeder
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Vijayaratnam Santhakumar
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Manon Valiquette
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Johan Sandin
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Daniel Widzowski
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
| | - Jennifer Laird
- AstraZeneca, Neuroscience, Innovative Medicines & Early Development, Waltham, MA 02451, United States
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5
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Joseph L, Thomsen M. Effects of muscarinic receptor antagonists on cocaine discrimination in wild-type mice and in muscarinic receptor M 1, M 2, and M 4 receptor knockout mice. Behav Brain Res 2017; 329:75-83. [PMID: 28442355 DOI: 10.1016/j.bbr.2017.04.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 04/06/2017] [Accepted: 04/11/2017] [Indexed: 01/14/2023]
Abstract
Muscarinic M1/M4 receptor stimulation can reduce abuse-related effects of cocaine and may represent avenues for treating cocaine addiction. Muscarinic antagonists can mimic and enhance effects of cocaine, including discriminative stimulus (SD) effects, but the receptor subtypes mediating those effects are not known. A better understanding of the complex cocaine/muscarinic interactions is needed to evaluate and develop potential muscarinic-based medications. Here, knockout mice lacking M1, M2, or M4 receptors (M1-/-, M2-/-, M4-/-), as well as control wild-type mice and outbred Swiss-Webster mice, were trained to discriminate 10mg/kg cocaine from saline. Muscarinic receptor antagonists with no subtype selectivity (scopolamine), or preferential affinity at the M1, M2, or M4 subtype (telenzepine, trihexyphenidyl; methoctramine, AQ-RA 741; tropicamide) were tested alone and in combination with cocaine. In intact animals, antagonists with high affinity at M1/M4 receptors partially substituted for cocaine and increased the SD effect of cocaine, while M2-preferring antagonists did not substitute, and reduced the SD effect of cocaine. The cocaine-like effects of scopolamine were absent in M1-/- mice. The cocaine SD attenuating effects of methoctramine were absent in M2-/- mice and almost absent in M1-/- mice. The findings indicate that the cocaine-like SD effects of muscarinic antagonists are primarily mediated through M1 receptors, with a minor contribution of M4 receptors. The data also support our previous findings that stimulation of M1 receptors and M4 receptors can each attenuate the SD effect of cocaine, and show that this can also be achieved by blocking M2 autoreceptors, likely via increased acetylcholine release.
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Affiliation(s)
- Lauren Joseph
- Alcohol and Drug Abuse Research Center, McLean Hospital/Harvard Medical School, Belmont, MA, USA
| | - Morgane Thomsen
- Alcohol and Drug Abuse Research Center, McLean Hospital/Harvard Medical School, Belmont, MA, USA; Laboratory of Neuropsychiatry, Psychiatric Centre Copenhagen and University of Copenhagen, Copenhagen, Denmark.
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Abstract
Xanomeline (1) is an orthosteric muscarinic acetylcholine receptor (mAChR) agonist, often referred to as M1/M4-preferring, that received widespread attention for its clinical efficacy in schizophrenia and Alzheimer's disease (AD) patients. Despite the compound's promising initial clinical results, dose-limiting side effects limited further clinical development. While xanomeline, and related orthosteric muscarinic agonists, have yet to receive approval from the FDA for the treatment of these CNS disorders, interest in the compound's unique M1/M4-preferring mechanism of action is ongoing in the field of chemical neuroscience. Specifically, the promising cognitive and behavioral effects of xanomeline in both schizophrenia and AD have spurred a renewed interest in the development of safer muscarinic ligands with improved subtype selectivity for either M1 or M4. This Review will address xanomeline's overall importance in the field of neuroscience, with a specific focus on its chemical structure and synthesis, pharmacology, drug metabolism and pharmacokinetics (DMPK), and adverse effects.
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Affiliation(s)
- Aaron M. Bender
- Vanderbilt
Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Carrie K. Jones
- Vanderbilt
Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department
of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Craig W. Lindsley
- Vanderbilt
Center for Neuroscience Drug Discovery, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department
of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Department
of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232, United States
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7
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Bongiovanni R, Kyser AN, Jaskiw GE. Tyrosine depletion lowers in vivo DOPA synthesis in ventral hippocampus. Eur J Pharmacol 2012; 696:70-6. [PMID: 23022716 DOI: 10.1016/j.ejphar.2012.09.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 09/05/2012] [Accepted: 09/17/2012] [Indexed: 10/27/2022]
Abstract
In vivo dopamine synthesis in the medial prefrontal cortex of the rat is sensitive to the availability of tyrosine. Whether other limbic cortical dopamine terminal regions are similarly tyrosine-dependent is not known. In this study we examined the effects of tyrosine depletion on dopamine synthesis and catecholamine levels in the ventral hippocampus. A tyrosine- and phenylalanine-free neutral amino acid mixture was used to lower brain tyrosine levels in rats undergoing in vivo microdialysis. In one group, NSD-1015 was included in perfusate to permit measurement of DOPA levels. In a second group, NSD-1015 was not included in perfusate so that catecholamine levels could be assayed. Tyrosine depletion significantly lowered DOPA levels in the NSD-1015 treated group and lowered DOPAC but not dopamine or noradrenaline levels in the group not exposed to NSD-1015. We conclude that while catecholamine synthesis in the ventral hippocampus declines when tyrosine availability is lowered, under basal conditions, compensatory mechanisms are able to maintain stable extracellular catecholamine levels.
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Affiliation(s)
- Rodolfo Bongiovanni
- Psychiatry Service, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd., Cleveland, Ohio 44106, USA.
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8
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Noori HR, Fliegel S, Brand I, Spanagel R. The impact of acetylcholinesterase inhibitors on the extracellular acetylcholine concentrations in the adult rat brain: A meta-analysis. Synapse 2012; 66:893-901. [DOI: 10.1002/syn.21581] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 06/19/2012] [Indexed: 01/23/2023]
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Abstract
Schizophrenia is a devastating disease with several broad symptom clusters and the current monoamine-based treatments do not adequately treat the disease, especially negative and cognitive symptoms. A proposed alternative approach for treating schizophrenia is through the use of compounds that activate certain muscarinic receptor subtypes, the so-called muscarinic cholinergic hypothesis theory. This theory has been revitalized with a number of recent and provocative findings including postmortem reports in schizophrenia patients showing decreased numbers of muscarinic M(1) and M(4) receptors in brain regions associated with schizophrenia as well as decreased muscarinic receptors in an in vivo imaging study. Studies with M(4) knockout mice have shown that there is a reciprocal relationship between M(4) and dopamine receptor function, and a number of muscarinic agonists have shown antidopaminergic activity in a variety of preclinical assays predictive of antipsychotic efficacy in the clinic. Furthermore, the M(1)/M(4) preferring partial agonist xanomeline has been shown to have antipsychotic-like and pro-cognitive activity in preclinical models and in clinical trials to decrease psychotic-like behaviors in Alzheimer's patients and positive, negative, and cognitive symptoms in patients with schizophrenia. Therefore, we propose that an agonist with M(1) and M(4) interactions would effectively treat core symptom clusters associated with schizophrenia. Currently, research is focused on developing subtype-selective muscarinic agonists and positive allosteric modulators that have reduced propensity for parasympathetic side-effects, but retain the therapeutic benefit observed with their less selective predecessors.
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Affiliation(s)
- David L McKinzie
- Lilly Research Laboratories, Eli Lilly and Co., Indianapolis, IN 46285, USA.
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10
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Muscarinic and nicotinic acetylcholine receptor agonists and allosteric modulators for the treatment of schizophrenia. Neuropsychopharmacology 2012; 37:16-42. [PMID: 21956443 PMCID: PMC3238081 DOI: 10.1038/npp.2011.199] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Muscarinic and nicotinic acetylcholine (ACh) receptors (mAChRs and nAChRs) are emerging as important targets for the development of novel treatments for the symptoms associated with schizophrenia. Preclinical and early proof-of-concept clinical studies have provided strong evidence that activators of specific mAChR (M(1) and M(4)) and nAChR (α(7) and α(2)β(4)) subtypes are effective in animal models of antipsychotic-like activity and/or cognitive enhancement, and in the treatment of positive and cognitive symptoms in patients with schizophrenia. While early attempts to develop selective mAChR and nAChR agonists provided important preliminary findings, these compounds have ultimately failed in clinical development due to a lack of true subtype selectivity and subsequent dose-limiting adverse effects. In recent years, there have been major advances in the discovery of highly selective activators for the different mAChR and nAChR subtypes with suitable properties for optimization as potential candidates for clinical trials. One novel strategy has been to identify ligands that activate a specific receptor subtype through actions at sites that are distinct from the highly conserved ACh-binding site, termed allosteric sites. These allosteric activators, both allosteric agonists and positive allosteric modulators, of mAChR and nAChR subtypes demonstrate unique mechanisms of action and high selectivity in vivo, and may provide innovative treatment strategies for schizophrenia.
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11
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Bolbecker AR, Shekhar A. Muscarinic agonists and antagonists in schizophrenia: recent therapeutic advances and future directions. Handb Exp Pharmacol 2012:167-190. [PMID: 22222699 DOI: 10.1007/978-3-642-23274-9_8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Existing therapies for schizophrenia have limited efficacy, and significant residual positive, negative, and cognitive symptoms remain in many individuals with the disorder even after treatment with the current arsenal of antipsychotic drugs. Preclinical and clinical data suggest that selective activation of the muscarinic cholinergic system may represent novel therapeutic mechanisms for the treatment of schizophrenia. The therapeutic relevance of earlier muscarinic agonists was limited by their lack of receptor selectivity and adverse event profile arising from activation of nontarget muscarinic receptors. Recent advances in developing compounds that are selective to muscarinic receptor subtypes or activate allosteric receptor sites offer tremendous promise for therapeutic targeting of specific muscarinic receptor subtypes in schizophrenia.
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Affiliation(s)
- Amanda R Bolbecker
- Psychological and Brain Sciences, Indiana University, 1101 East Tenth Street, Bloomington, IN 47405-7007, USA
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12
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Field JR, Walker AG, Conn PJ. Targeting glutamate synapses in schizophrenia. Trends Mol Med 2011; 17:689-98. [PMID: 21955406 DOI: 10.1016/j.molmed.2011.08.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 08/12/2011] [Accepted: 08/19/2011] [Indexed: 12/25/2022]
Abstract
Although early clinical observations implicated dopamine dysfunction in the neuropathology of schizophrenia, accumulating evidence suggests that multiple neurotransmitter pathways are dysregulated. The psychotomimetic actions of NMDA receptor antagonists point to an imbalance of glutamatergic signaling. Encouragingly, numerous preclinical and clinical studies have elucidated several potential targets for increasing NMDA receptor function and equilibrating glutamatergic tone, including the metabotropic glutamate receptors 2, 3 and 5, the muscarinic acetylcholine receptors M(1) and M(4), and the glycine transporter GlyT1. Highly specific allosteric and orthosteric ligands have been developed that modify the activity of these novel target proteins, and in this review we summarize both the glutamatergic mechanisms and the novel compounds that are increasing the promise for a multifaceted pharmacological approach to treat schizophrenia.
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Affiliation(s)
- Julie R Field
- Department of Pharmacology and Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37212, USA
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13
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Ago Y. [Beneficial effect of galantamine on sensory information-processing deficits]. YAKUGAKU ZASSHI 2010; 130:1305-10. [PMID: 20930482 DOI: 10.1248/yakushi.130.1305] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clinical studies show that galantamine, a weak acetylcholine (ACh) esterase inhibitor and allosteric potentiator of nicotinic ACh receptors (nAChRs), improves negative and cognitive symptoms in schizophrenia, while donepezil, a potent ACh esterase inhibitor, does not. We have recently found that galantamine, but not donepezil, reversed isolation rearing-induced deficits of prepulse inhibition (PPI), sensory information-processing deficits, in mice. In addition, we unexpectedly found that the galantamine-induced improvements in PPI deficits were prevented by the muscarinic ACh receptor (mAChR) antagonists scopolamine and telenzepine (preferential for M(1) subtype), but not by the nAChR antagonists. Galantamine, like donepezil, increased extracellular ACh levels in the prefrontal cortex. However, donepezil, unlike galantamine, inhibited M(1)-mAChR-mediated Ca(2+) signal in human neuroblastoma SH-SY5Y. These results suggest that galantamine improves isolation rearing-induced PPI deficits via an activation of mAChRs and the difference in the effect on the PPI deficits between galantamine and donepezil is due to that in their action on M(1)-mAChRs. The possible mechanisms for the beneficial effect of galantamine are discussed in a model of isolation rearing-induced PPI deficits.
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Affiliation(s)
- Yukio Ago
- Laboratory of Medicinal Pharmacology, Graduate School of Pharmaceutical Sciences, Osaka University, Yamada-oka, Suita, Japan.
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Digby GJ, Shirey JK, Conn PJ. Allosteric activators of muscarinic receptors as novel approaches for treatment of CNS disorders. MOLECULAR BIOSYSTEMS 2010; 6:1345-54. [PMID: 20582339 PMCID: PMC4780333 DOI: 10.1039/c002938f] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Muscarinic acetylcholine receptors (mAChRs) represent exciting therapeutic targets for the treatment of multiple CNS disorders. The high degree of conservation of amino acids comprising the orthosteric acetylcholine (ACh) binding site between individual mAChR subtypes has hindered the development of subtype-selective compounds that bind to this site. As a result, many academic and industry researchers are now focusing on developing allosteric activators of mAChRs including both positive allosteric modulators (PAMs) and allosteric agonists. In the past 10 years major advances have been achieved in the discovery of allosteric ligands that possess much greater selectivity for individual mAChR subtypes when compared to previously developed orthosteric agents. These novel allosteric modulators of mAChRs may provide therapeutic potential for treatment of a number of CNS disorders such as Alzheimer's disease and schizophrenia.
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Affiliation(s)
- Gregory J. Digby
- 1215 Light Hall, 2215B Garland Ave., Nashville, TN 37237-0575, USA. ; Fax: +1 615 343 3088; Tel: +1 615 322 6730
| | - Jana K. Shirey
- 8410E Medical Research Building IV, 2215B Garland Ave., Nashville, TN 37237-0575, USA. ; Fax: +1 615 936-2661; Tel: +1 615 936-8424
| | - P. Jeffrey Conn
- 2215B Garland Ave., Nashville, TN 37237-0575, USA. ; Fax: +1 615 343 3088; Tel: +1 615 322 6730
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Zhang ZW, Burke MW, Calakos N, Beaulieu JM, Vaucher E. Confocal Analysis of Cholinergic and Dopaminergic Inputs onto Pyramidal Cells in the Prefrontal Cortex of Rodents. Front Neuroanat 2010; 4:21. [PMID: 20589096 PMCID: PMC2893003 DOI: 10.3389/fnana.2010.00021] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 05/05/2010] [Indexed: 11/13/2022] Open
Abstract
Cholinergic and dopaminergic projections to the rat medial prefrontal cortex (mPFC) are both involved in cognitive functions including attention. These neuronal systems modulate mPFC neuronal activity mainly through diffuse transmission. In order to better understand the anatomical level of influence of these systems, confocal microscopy with triple-fluorescent immunolabeling was used in three subregions of the mPFC of rats and Drd1a-tdTomato/Drd2-EGFP transgenic mice. The zone of interaction was defined as a reciprocal microproximity between dopaminergic and cholinergic axonal segments as well as pyramidal neurons. The density of varicosities, along these segments was considered as a possible activity-dependant morphological feature. The percentage of cholinergic and dopaminergic fibers in microproximity ranged from 12 to 40% depending on the layer and mPFC subregion. The cholinergic system appeared to have more influence on dopaminergic fibers since a larger proportion of the dopaminergic fibers were within microproximity to cholinergic fibers. The density of both cholinergic and dopaminergic varicosities was significantly elevated within microproximities. The main results indicate that the cholinergic and dopaminergic systems converge on pyramidal cells in mPFC particularly in the layer V. In transgenic mice 93% of the pyramidal cells expressed the transgenic marker for Drd2 expression, but only 22% expressed the maker for Drd1ar expression. Data presented here suggest that the modulation of mPFC by dopaminergic fibers would be mostly inhibitory and localized at the output level whereas the cholinergic modulation would be exerted at the input and output level both through direct interaction with pyramidal cells and dopaminergic fibers.
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Affiliation(s)
- Zi-Wei Zhang
- School of Optometry, Université de Montréal Montréal, QC, Canada
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16
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Abstract
Acetylcholine plays a major role in mediating attention processes. We investigated the muscarinic antagonist effect of scopolamine on functional neuro-anatomy of attention and cognition. We assessed 12 healthy volunteers while performing the Attention Network Task on 0.4 mg scopolamine and placebo in a single-blind randomized trial in a 1.5 T magnetic resonance scanner. Neurocognitive measures included verbal learning, verbal memory, verbal fluency, trail making, digit span, a continuous performance task and a planning task (Tower of London). When compared to placebo, scopolamine increased reaction times for conflicting stimulus processing, together with decreasing brain activation in the anterior cingulate cortex (a brain region involved in conflict processing) suggestive of a muscarinic antagonist effect on executive control of attention. Contrary to the notion of a predominantly right-hemispheric lateralization of cognitive processes associated with orienting attention, scopolamine reduced brain activity in left superior and left middle frontal brain areas. Our neuropsychological test data revealed a selective effect of scopolamine on verbal learning and memory while other cognitive domains, such as planning and working memory, were unaffected. These findings are consistent with muscarinic modulation of dopaminergic neurotransmission in frontal attention networks when processing conflicting information.
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17
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Li Z, Prus AJ, Dai J, Meltzer HY. Differential effects of M1 and 5-hydroxytryptamine1A receptors on atypical antipsychotic drug-induced dopamine efflux in the medial prefrontal cortex. J Pharmacol Exp Ther 2009; 330:948-55. [PMID: 19491322 DOI: 10.1124/jpet.109.155663] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Systemic administration of the M(1) receptor agonists N-desmethylclozapine (NDMC) and 4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one (AC260584) increase dopamine (DA) efflux in rat medial prefrontal cortex (mPFC). This increase is blocked by systemic administration of both telenzepine, a preferential M(1) receptor antagonist, and N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexanecarboxamide (WAY-100635), a 5-hydroxytryptamine(1A) receptor antagonist. The present study sought to determine whether DA efflux in the mPFC induced by the atypical antipsychotic drugs clozapine, risperidone, and olanzapine is also mediated by M(1) receptor stimulation and, specifically, to determine whether these effects are mediated M(1) receptors in the mPFC through use of in vivo microdialysis in awake, freely moving Sprague-Dawley rats. Telenzepine (3 mg/kg) significantly attenuated clozapine- (20 mg/kg), olanzapine- (10 mg/kg), and risperidone- (1.0 mg/kg) induced increases in mPFC DA efflux. Local mPFC perfusion of NDMC, AC260584, clozapine, risperidone, or olanzapine (10-500 microM), significantly increased DA efflux in the mPFC. Local mPFC perfusion of telenzepine (0.1 microM) prevented increases in mPFC DA efflux induced by systemic administration of AC260584 (10 mg/kg), NDMC (20 mg/kg), and clozapine (10 mg/kg), but not by risperidone (1.0 mg/kg) or olanzapine (10 mg/kg). However, local mPFC perfusion of WAY-100635 (0.1 microM) prevented mPFC DA efflux induced by clozapine, risperidone, and olanzapine, but not by AC260584 or NDMC. These results suggest that the AC260584-, NDMC-, and clozapine-induced DA efflux in the mPFC is mediated directly by mPFC M(1) receptors.
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Affiliation(s)
- Zhu Li
- Psychiatry Department, Vanderbilt University School of Medicine, 1601 23rd Ave. South, 3035, Nashville, TN 37212, USA.
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du Bois TM, Newell KA, Han M, Deng C, Huang XF. Perinatal PCP treatment alters the developmental expression of prefrontal and hippocampal muscarinic receptors. Prog Neuropsychopharmacol Biol Psychiatry 2009; 33:37-40. [PMID: 18940225 DOI: 10.1016/j.pnpbp.2008.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 10/01/2008] [Accepted: 10/01/2008] [Indexed: 10/21/2022]
Abstract
Perinatal phencyclidine (PCP) treatment has been used to model brain pathological processes that may be present in schizophrenia such as increased apoptosis during early brain development, and long-term alterations in expression of parvalbumin-containing interneurons and glutamatergic N-methyl-D-aspartate (NMDA) receptors. We report that this treatment also affects receptor expression of another excitatory neurotransmitter receptor, the muscarinic receptor. Female rat pups received injections of the NMDA receptor antagonist PCP (10 mg/kg, s.c.) or saline on postnatal days (PN)7, 9 and 11. [3H]Pirenzepine binding to M1/4 receptors was examined at four time-points (PN12, 18, 32 and 96) following treatment cessation. Significant effects of treatment on [3H]pirenzepine binding were evident immediately after treatment cessation with a decrease in PCP-treated rats at PN12 in the prefrontal cortex (-24%, p<0.05) and hippocampus (-19%, p<0.05). After this initial decrease, binding subsequently increased to 47% above control levels in the prefrontal cortex of adolescent animals, which remained elevated in adulthood (+10%, p<0.05), while in the hippocampus there was a trend towards increased binding in adolescent animals and no change thereafter. This work adds to findings demonstrating that perinatal PCP exposure leads to long-term imbalance of excitatory and inhibitory neurotransmitter systems, supporting its relevance as a developmental model of schizophrenia pathology. Alterations in muscarinic receptor expression may contribute specifically to the cognitive impairments reported to occur after perinatal NMDA receptor antagonist treatment.
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Meltzer HY, Sumiyoshi T. Does stimulation of 5-HT1A receptors improve cognition in schizophrenia? Behav Brain Res 2008; 195:98-102. [DOI: 10.1016/j.bbr.2008.05.016] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Accepted: 05/23/2008] [Indexed: 11/28/2022]
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Li Z, Snigdha S, Roseman AS, Dai J, Meltzer HY. Effect of muscarinic receptor agonists xanomeline and sabcomeline on acetylcholine and dopamine efflux in the rat brain; comparison with effects of 4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one (AC260584) and N-desmethylclozapine. Eur J Pharmacol 2008; 596:89-97. [DOI: 10.1016/j.ejphar.2008.08.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Revised: 07/08/2008] [Accepted: 08/16/2008] [Indexed: 10/21/2022]
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Martinez V, Sarter M. Detection of the moderately beneficial cognitive effects of low-dose treatment with haloperidol or clozapine in an animal model of the attentional impairments of schizophrenia. Neuropsychopharmacology 2008; 33:2635-47. [PMID: 18094665 DOI: 10.1038/sj.npp.1301661] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The absence of effective cognition enhancers for the treatment of patients with schizophrenia limits the validation of animal models and behavioral tests used for drug finding and characterization. However, low doses of haloperidol and clozapine were documented to produce moderately beneficial effects in patients. Therefore, this experiment was designed to determine the attentional effects of such treatments in a repeated-amphetamine (AMPH) animal model. Animals were trained in an operant-sustained attention task and underwent a 40-day pretreatment period with saline or increasing doses (1-10 mg per kg) of AMPH. After regaining baseline performance following 10 days of saline treatment, animals were treated with haloperidol (0.025 mg per kg), clozapine (2.5 mg per kg), or vehicle for 10 days. Furthermore, the effects of AMPH challenges (1.0 mg per kg) were assessed. In AMPH-pretreated animals, the administration of AMPH challenges resulted in the disruption of attentional performance. Treatment with haloperidol and clozapine attenuated the detrimental performance effects of these challenges, with clozapine exhibiting more robust attenuation. Furthermore, clozapine, but not haloperidol, impaired the performance of control animals. In contrast, the performance of AMPH-pretreated animals remained unaffected by clozapine. As this animal model detects the moderately beneficial cognitive effects of haloperidol and clozapine, it may be useful for preclinical research designed to detect and characterize treatments for the cognitive symptoms of schizophrenia.
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Affiliation(s)
- Vicente Martinez
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA
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