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Canning BJ, Liu Q, Tao M, DeVita R, Perelman M, Hay DW, Dicpinigaitis PV, Liang J. Evidence for Alpha 7 Nicotinic Receptor Activation During the Cough Suppressing Effects Induced by Nicotine and Identification of ATA-101 as a Potential Novel Therapy for the Treatment of Chronic Cough. J Pharmacol Exp Ther 2022; 380:94-103. [PMID: 34782407 PMCID: PMC8969114 DOI: 10.1124/jpet.121.000641] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 11/11/2021] [Indexed: 02/03/2023] Open
Abstract
Studies performed in healthy smokers have documented a diminished responsiveness to tussive challenges, and several lines of experimental evidence implicate nicotine as an antitussive component in both cigarette smoke and the vapors generated by electronic cigarettes (eCigs). We set out to identify the nicotinic receptor subtype involved in the antitussive actions of nicotine and to further evaluate the potential of nicotinic receptor-selective agonists as cough-suppressing therapeutics. We confirmed an antitussive effect of nicotine in guinea pigs. We additionally observed that the alpha-4 beta-2 (α 4 β 2)-selective agonist Tc-6683 was without effect on evoked cough responses in guinea pigs, while the α 7-selective agonist PHA 543613 dose-dependently inhibited evoked coughing. We subsequently describe the preclinical evidence in support of ATA-101, a potent and highly selective (α 7) selective nicotinic receptor agonist, as a potential candidate for antitussive therapy in humans. ATA-101, formerly known as Tc-5619, was orally bioavailable and moderately central nervous system (CNS) penetrant and dose-dependently inhibited coughing in guinea pigs evoked by citric acid and bradykinin. Comparing the effects of airway targeted administration versus systemic dosing and the effects of repeated dosing at various times prior to tussive challenge, our data suggest that the antitussive actions of ATA-101 require continued engagement of α 7 nicotinic receptors, likely in the CNS. Collectively, the data provide the preclinical rationale for α 7 nicotinic receptor engagement as a novel therapeutic strategy for cough suppression. The data also suggest that α 7 nicotinic acetylcholine receptor (nAChR) activation by nicotine may be permissive to nicotine delivery in a way that may promote addiction. SIGNIFICANCE STATEMENT: This study documents the antitussive actions of nicotine and identifies the α7 nicotinic receptor subtype as the target for nicotine during cough suppression described in humans. We additionally present evidence suggesting that ATA-101 and other α7 nicotinic receptor-selective agonists may be promising candidates for the treatment of chronic refractory cough.
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Affiliation(s)
- Brendan J Canning
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Qi Liu
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Mayuko Tao
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Robert DeVita
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Michael Perelman
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Douglas W Hay
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Peter V Dicpinigaitis
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
| | - Jing Liang
- The Johns Hopkins Asthma and Allergy Center, Baltimore, Maryland (B.J.C, Q.L.); Tokyo Medical and Dental University, Tokyo, Japan (M.T.); RJD Medicinal Chemistry Consulting LLC, Westfield, New Jersey (R.D.); Michael Perelman Consulting, Winter Park, Florida (M.P.); Hay Drug Discovery Consulting, Valley Forge, Pennsylvania (D.W.H.); Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York (P.V.D.); Apple Helix Bioventures, New York, New York (J.L.)
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Adolescent nicotine challenge promotes the future vulnerability to opioid addiction: Involvement of lateral paragigantocellularis neurons. Life Sci 2019; 234:116784. [DOI: 10.1016/j.lfs.2019.116784] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/11/2019] [Accepted: 08/20/2019] [Indexed: 02/03/2023]
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Tao M, Liu Q, Miyazaki Y, Canning BJ. Nicotinic receptor dependent regulation of cough and other airway defensive reflexes. Pulm Pharmacol Ther 2019; 58:101810. [PMID: 31181318 DOI: 10.1016/j.pupt.2019.101810] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 06/05/2019] [Accepted: 06/06/2019] [Indexed: 11/30/2022]
Abstract
Nicotinic receptor activation in the airways evokes airway defensive reflexes including cough. These reflexes are the direct result of bronchopulmonary afferent nerve activation, which may occur directly, through activation of nicotinic receptors expressed on the terminals of airway sensory nerves, or indirectly, secondary to the end organ effects associated with autonomic nerve stimulation. The irritating effects of nicotine delivered topically to the airways are counterbalanced by an inhibitory effect of nicotinic receptor activation in the central nervous system. We present evidence that these nicotinic receptors are components of essential transducing and encoding mechanisms regulating airway defense.
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Affiliation(s)
- Mayuko Tao
- Tokyo Medical & Dental University, Japan
| | - Qi Liu
- Johns Hopkins Asthma and Allergy Center, Baltimore, MD, USA
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Falip M, Rodriguez-Bel L, Castañer S, Sala-Padró J, Miro J, Jaraba S, Casasnovas C, Morandeira F, Berdejo J, Carreño M. Hippocampus and Insula Are Targets in Epileptic Patients With Glutamic Acid Decarboxylase Antibodies. Front Neurol 2019; 9:1143. [PMID: 30687213 PMCID: PMC6334555 DOI: 10.3389/fneur.2018.01143] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 12/11/2018] [Indexed: 11/13/2022] Open
Abstract
Background: Antibodies to glutamic acid decarboxylase (GAD ab) have been found in patients with limbic encephalitis (LE) and chronic pharmacoresistant focal epilepsy (FE). The objectives of the study were to: (1) analyze the clinical and neuroimaging course of patients with FE+GAD ab, (2) compare these characteristics with a control group, and (3) describe the most affected cerebral areas with structural and functional imaging. Methods: Patients with FE + high titers of GAD ab and a follow-up of at least 5 years were selected. Titers of serum GAD ab exceeding 2,000 UI/ml were considered high. Evolutive clinical and radiological characteristics were studied in comparison to two different control groups: patients with bilateral or with unilateral mesial temporal sclerosis (BMTS or UMTS) of a non-autoimmune origin. Results: A group of 13 patients and 17 controls were included (8 BMTS, 9 UMTS). The most frequent focal aware seizures (FAS) reported by patients were psychic (5/13: 33%). Somatosensorial, motor, and visual FAS (4/13:32%) (p: 0.045), musicogenic reflex seizures (MRS), and a previous history of cardiac syncope were reported only patients (2/13:16% each) (p: NS). Comparing EEG characteristics between patients and controls, a more widespread distribution of interictal epileptiform discharges (IED) was observed in FE+ GAD ab patients than in controls (p:0.01). Rhythmic delta activity was observed in all controls in anterior temporal lobes while in patients this was less frequent (p: 0.001). No IED, even in 24 h cVEEG, was seen in 6 patients (46%).First MRI was normal in 4/5 (75%) patients. During the follow-up mesial temporal lobe (MTsL) sclerosis was observed in 5/8 (62%) of patients. All patients had abnormal FDG-PET study. MTL hypometabolism was observed in 10/11 (91%) patients, being bilateral in 7/11 (63%). In controls, this was observed in 16/17 (94%), and it was bilateral in 8/17 (47%) (p: NS). Insular hypometabolism was observed in 5/11 (45%) patients (P:0.002). Conclusions: Clinical, EEG, and FDG-PET findings in FE+GAD ab suggest a widespread disease not restricted to the temporal lobe. Progressive MTL sclerosis may be observed during follow-up. In comparison to what is found in patients with non-autoimmune MTL epilepsy, insular hypometabolism is observed only in patients with GAD ab, so it may be an important diagnostic clue.
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Affiliation(s)
- Mercè Falip
- Epilepsy Unit, Department of Neurology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Laura Rodriguez-Bel
- PET Division, Institute of Diagnostic Imaging (IDI), Hospital de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Sara Castañer
- MRI Division, Institute of Diagnostic Imaging (IDI), Hospital de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Jacint Sala-Padró
- Epilepsy Unit, Department of Neurology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Júlia Miro
- Epilepsy Unit, Department of Neurology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Sónia Jaraba
- Epilepsy Unit, Department of Neurology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Carlos Casasnovas
- Neuromuscular Unit, Department of Neurology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Francisco Morandeira
- Immunology Unit, Biochemistry Department, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Javier Berdejo
- Department of Cardiology, Hospital Universitari de Bellvitge, Hospitalet de Llobregat, Barcelona, Spain
| | - Mar Carreño
- Epilepsy Unit, Department of Neurology, Hospital Clinic i Provincial, Barcelona, Spain
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A Novel Multisensory Integration Task Reveals Robust Deficits in Rodent Models of Schizophrenia: Converging Evidence for Remediation via Nicotinic Receptor Stimulation of Inhibitory Transmission in the Prefrontal Cortex. J Neurosci 2017; 36:12570-12585. [PMID: 27974613 DOI: 10.1523/jneurosci.1628-16.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 09/20/2016] [Accepted: 10/19/2016] [Indexed: 12/24/2022] Open
Abstract
Atypical multisensory integration is an understudied cognitive symptom in schizophrenia. Procedures to evaluate multisensory integration in rodent models are lacking. We developed a novel multisensory object oddity (MSO) task to assess multisensory integration in ketamine-treated rats, a well established model of schizophrenia. Ketamine-treated rats displayed a selective MSO task impairment with tactile-visual and olfactory-visual sensory combinations, whereas basic unisensory perception was unaffected. Orbitofrontal cortex (OFC) administration of nicotine or ABT-418, an α4β2 nicotinic acetylcholine receptor (nAChR) agonist, normalized MSO task performance in ketamine-treated rats and this effect was blocked by GABAA receptor antagonism. GABAergic currents were also decreased in OFC of ketamine-treated rats and were normalized by activation of α4β2 nAChRs. Furthermore, parvalbumin (PV) immunoreactivity was decreased in the OFC of ketamine-treated rats. Accordingly, silencing of PV interneurons in OFC of PV-Cre mice using DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) selectively impaired MSO task performance and this was reversed by ABT-418. Likewise, clozapine-N-oxide-induced inhibition of PV interneurons in brain slices was reversed by activation of α4β2 nAChRs. These findings strongly imply a role for prefrontal GABAergic transmission in the integration of multisensory object features, a cognitive process with relevance to schizophrenia. Accordingly, nAChR agonism, which improves various facets of cognition in schizophrenia, reversed the severe MSO task impairment in this study and appears to do so via a GABAergic mechanism. Interactions between GABAergic and nAChR receptor systems warrant further investigation for potential therapeutic applications. The novel behavioral procedure introduced in the current study is acutely sensitive to schizophrenia-relevant cognitive impairment and should prove highly valuable for such research. SIGNIFICANCE STATEMENT Adaptive behaviors are driven by integration of information from different sensory modalities. Multisensory integration is disrupted in patients with schizophrenia, but little is known about the neural basis of this cognitive symptom. Development and validation of multisensory integration tasks for animal models is essential given the strong link between functional outcome and cognitive impairment in schizophrenia. We present a novel multisensory object oddity procedure that detects selective multisensory integration deficits in a rat model of schizophrenia using various combinations of sensory modalities. Moreover, converging data are consistent with a nicotinic-GABAergic mechanism of multisensory integration in the prefrontal cortex, results with strong clinical relevance to the study of cognitive impairment and treatment in schizophrenia.
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Khakpay R, Azaddar M, Khakpay F, Hatami Nemati H. Analgesic Effect of 17β-Estradiol on Nucleus Paragigantocellularis Lateralis of Male Rats Mediated Via GABA A Receptors. Basic Clin Neurosci 2017; 8:51-60. [PMID: 28446950 PMCID: PMC5396174 DOI: 10.15412/j.bcn.03080107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Introduction: Beside its autonomic functions, the nucleus paragigantocellularis lateralis (LPGi) is involved in the descending pain modulation. 17β-Estradiol is a neuroactive steroid found in several brain areas such as LPGi. Intra-LPGi microinjection of 17β-estradiol can elicit the analgesic responses. 17β-Estradiol modulates nociception by binding to estrogenic receptors as well as allosteric interaction with other membrane-bound receptors like GABAA receptors. This study aimed to examine the role of GABAA receptors in the pain modulating effect of intra-LPGi injection of 17β-estradiol. Methods: To study the antinociceptive effects of 17β-estradiol, cannulation into the LPGi nucleus of male Wistar rats was performed. About 500 nL of drug was administered 15 minutes prior to formalin injection (50 μL of 4%). Then, formalin-induced flexing and licking behaviors were recorded for 60 minutes. For evaluating the role of GABAA receptors in the estradiol-induced pain modulation, 17β-estradiol was administered into the LPGi nucleus 15 minutes after the injection of 25 ng/μL bicuculline (the GABAA receptor antagonist). Then, the formalin-induced responses were recorded. Results: The results of the current study showed that intra-LPGi injection of 17β-estradiol decreased the flexing duration in both phases of formalin test (P<0.001); but it only attenuated the second phase of licking behavior (P<0.001). 17β-estradiol attenuated the second phase of formalin test of both behaviors (P<0.001). Bicuculline prevented the antinociceptive effect of intra-LPGi 17β-estradiol in both first and second phases of formalin-induced responses (P<0.001). Conclusion: According to the results of this study, the analgesic effect of intra-LPGi 17β-estradiol on the formalin-induced inflammatory pain might be mediated via GABAA receptors.
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Affiliation(s)
- Roghaieh Khakpay
- Department of Animal Science, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Maryam Azaddar
- Department of Animal Science, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
| | - Fatemeh Khakpay
- Department of Biology, Faculty of Basics Sciences, Varamin Branch, Islamic Azad University, Pishva, Iran
| | - Homeira Hatami Nemati
- Department of Animal Science, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran
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Zhan Q, Buchanan GF, Motelow JE, Andrews J, Vitkovskiy P, Chen WC, Serout F, Gummadavelli A, Kundishora A, Furman M, Li W, Bo X, Richerson GB, Blumenfeld H. Impaired Serotonergic Brainstem Function during and after Seizures. J Neurosci 2016; 36:2711-22. [PMID: 26937010 PMCID: PMC4879214 DOI: 10.1523/jneurosci.4331-15.2016] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 01/11/2016] [Accepted: 01/23/2016] [Indexed: 12/30/2022] Open
Abstract
Impaired breathing, cardiac function, and arousal during and after seizures are important causes of morbidity and mortality. Previous work suggests that these changes are associated with depressed brainstem function in the ictal and post-ictal periods. Lower brainstem serotonergic systems are postulated to play an important role in cardiorespiratory changes during and after seizures, whereas upper brainstem serotonergic and other systems regulate arousal. However, direct demonstration of seizure-associated neuronal activity changes in brainstem serotonergic regions has been lacking. Here, we performed multiunit and single-unit recordings from medullary raphe and midbrain dorsal raphe nuclei in an established rat seizure model while measuring changes in breathing rate and depth as well as heart rate. Serotonergic neurons were identified by immunohistochemistry. Respiratory rate, tidal volume, and minute ventilation were all significantly decreased during and after seizures in this model. We found that population firing of neurons in the medullary and midbrain raphe on multiunit recordings was significantly decreased during the ictal and post-ictal periods. Single-unit recordings from identified serotonergic neurons in the medullary raphe revealed highly consistently decreased firing during and after seizures. In contrast, firing of midbrain raphe serotonergic neurons was more variable, with a mixture of increases and decreases. The markedly suppressed firing of medullary serotonergic neurons supports their possible role in simultaneously impaired cardiorespiratory function in seizures. Decreased arousal likely arises from depressed population activity of several neuronal pools in the upper brainstem and forebrain. These findings have important implications for preventing morbidity and mortality in people living with epilepsy. SIGNIFICANCE STATEMENT Seizures often cause impaired breathing, cardiac dysfunction, and loss of consciousness. The brainstem and, specifically, brainstem serotonin neurons are thought to play an important role in controlling breathing, cardiac function, and arousal. We used an established rat seizure model to study the overall neuronal activity in the brainstem as well as firing of specific serotonin neurons while measuring cardiorespiratory function. Our results demonstrated overall decreases in brainstem neuronal activity and marked downregulation of lower brainstem serotonin neuronal firing in association with decreased breathing and heart rate during and after seizures. These findings point the way toward new treatments to augment brainstem function and serotonin, aiming to prevent seizure complications and reduce morbidity and mortality in people living with epilepsy.
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Affiliation(s)
- Qiong Zhan
- Departments of Neurology, Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China, Department of Neurology, the Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, China
| | | | | | | | | | | | | | | | | | | | - Wei Li
- Departments of Neurology, Department of Neurosurgery, Jinling Hospital, School of Medicine Nanjing University, Nanjing Jiangsu 210002, China, and
| | - Xiao Bo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - George B Richerson
- Departments of Neurology and Molecular Physiology and Biophysics, and Veterans Affairs Medical Center, Iowa City, Iowa 52246
| | - Hal Blumenfeld
- Departments of Neurology, Neuroscience, and Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06520,
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Rowell TR, Tarran R. Will chronic e-cigarette use cause lung disease? Am J Physiol Lung Cell Mol Physiol 2015; 309:L1398-409. [PMID: 26408554 PMCID: PMC4683316 DOI: 10.1152/ajplung.00272.2015] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 09/22/2015] [Indexed: 12/22/2022] Open
Abstract
Chronic tobacco smoking is a major cause of preventable morbidity and mortality worldwide. In the lung, tobacco smoking increases the risk of lung cancer, and also causes chronic obstructive pulmonary disease (COPD), which encompasses both emphysema and chronic bronchitis. E-cigarettes (E-Cigs), or electronic nicotine delivery systems, were developed over a decade ago and are designed to deliver nicotine without combusting tobacco. Although tobacco smoking has declined since the 1950s, E-Cig usage has increased, attracting both former tobacco smokers and never smokers. E-Cig liquids (e-liquids) contain nicotine in a glycerol/propylene glycol vehicle with flavorings, which are vaporized and inhaled. To date, neither E-Cig devices, nor e-liquids, are regulated by the Food and Drug Administration (FDA). The FDA has proposed a deeming rule, which aims to initiate legislation to regulate E-Cigs, but the timeline to take effect is uncertain. Proponents of E-Cigs say that they are safe and should not be regulated. Opposition is varied, with some opponents proposing that E-Cig usage will introduce a new generation to nicotine addiction, reversing the decline seen with tobacco smoking, or that E-Cigs generally may not be safe and will trigger diseases like tobacco. In this review, we shall discuss what is known about the effects of E-Cigs on the mammalian lung and isolated lung cells in vitro. We hope that collating this data will help illustrate gaps in the knowledge of this burgeoning field, directing researchers toward answering whether or not E-Cigs are capable of causing disease.
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Affiliation(s)
- Temperance R Rowell
- Marsico Lung Institute and Department of Cell Biology & Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Robert Tarran
- Marsico Lung Institute and Department of Cell Biology & Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Abdala AP, Paton JFR, Smith JC. Defining inhibitory neurone function in respiratory circuits: opportunities with optogenetics? J Physiol 2015; 593:3033-46. [PMID: 25384785 PMCID: PMC4532524 DOI: 10.1113/jphysiol.2014.280610] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 10/30/2014] [Indexed: 12/22/2022] Open
Abstract
Pharmacological and mathematical modelling studies support the view that synaptic inhibition in mammalian brainstem respiratory circuits is essential for generating normal and stable breathing movements. GABAergic and glycinergic neurones are known components of these circuits but their precise functional roles have not been established, especially within key microcircuits of the respiratory pre-Bötzinger (pre-BötC) and Bötzinger (BötC) complexes involved in phasic control of respiratory pump and airway muscles. Here, we review briefly current concepts of relevant complexities of inhibitory synapses and the importance of synaptic inhibition in the operation of these microcircuits. We highlight results and limitations of classical pharmacological studies that have suggested critical functions of synaptic inhibition. We then explore the potential opportunities for optogenetic strategies that represent a promising new approach for interrogating function of inhibitory circuits, including a hypothetical wish list for optogenetic approaches to allow expedient application of this technology. We conclude that recent technical advances in optogenetics should provide a means to understand the role of functionally select and regionally confined subsets of inhibitory neurones in key respiratory circuits such as those in the pre-BötC and BötC.
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Affiliation(s)
- Ana Paula Abdala
- School of Physiology and Pharmacology, Bristol CardioVascular, Medical Science Building, University of BristolBristol, UK
| | - Julian F R Paton
- School of Physiology and Pharmacology, Bristol CardioVascular, Medical Science Building, University of BristolBristol, UK
| | - Jeffrey C Smith
- Cellular and Systems Neurobiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of HealthBethesda, MD, USA
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Localization of α7 nicotinic acetylcholine receptor immunoreactivity on GABAergic interneurons in layers I-III of the rat retrosplenial granular cortex. Neuroscience 2013; 252:443-59. [PMID: 23985568 DOI: 10.1016/j.neuroscience.2013.08.024] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/14/2013] [Accepted: 08/15/2013] [Indexed: 01/08/2023]
Abstract
The rat retrosplenial granular cortex (RSG) receives cholinergic input from the medial septum-diagonal band (MS-DB) of the cholinergic basal forebrain (CBF), with projections terminating in layers I-III of RSG. The modulatory effects of acetylcholine (ACh) on cortical GABAergic interneurons in these layers are mediated by α7 nicotinic acetylcholine receptors (α7nAChRs). α7nAChRs are most abundant in the cerebral cortex and are largely localized to GABAergic interneurons. However, the CBF projection to the RSG has not been studied in detail, and the cellular or subcellular distribution of α7nAChRs in the rat RSG remains unclear. The main objective of this study was to test that α7nAChRs reside on GABAergic interneurons in CBF terminal fields of the rat RSG. First, we set out to define the characteristics of CBF projections from the MS-DB to layers of the RSG using anterograde neural tracing and immunohistochemical labeling with cholinergic markers. These results revealed that the pattern of axon terminal labeling in layer Ia, as well as layer II/III of the RSG is remarkably similar to the pattern of cholinergic axons in the RSG. Next, we investigated the relationship between α7nAChRs, labeled using either α-bungarotoxin or α7nAChR antibody, and the local neurochemical environment by labeling surrounding cells with antibodies against glutamic acid decarboxylase (GAD), parvalbumin (PV) and reelin (a marker of the ionotropic serotonin receptor-expressing GABAergic interneurons). α7nAChRs were found to be localized on both somatodendritic and neuronal elements within subpopulations of GABAergic PV-, reelin-stained and non PV-stained neurons in layers I-III of the RSG. Finally, electron microscopy revealed that α7nAChRs are GAD- and PV-positive cytoplasmic and neuronal elements. These results strongly suggest that ACh released from CBF afferents is transmitted via α7nAChR to GAD-, PV-, and reelin-positive GABAergic interneurons in layers I-III of the RSG.
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Umana IC, Daniele CA, McGehee DS. Neuronal nicotinic receptors as analgesic targets: it's a winding road. Biochem Pharmacol 2013; 86:1208-14. [PMID: 23948066 DOI: 10.1016/j.bcp.2013.08.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/01/2013] [Accepted: 08/01/2013] [Indexed: 12/12/2022]
Abstract
Along with their well known role in nicotine addiction and autonomic physiology, neuronal nicotinic receptors (nAChRs) also have profound analgesic effects in animal models and humans. This is not a new idea, even in the early 1500s, soon after tobacco was introduced to the new world, its proponents listed pain relief among the beneficial properties of smoking. In recent years, analgesics that target specific nAChR subtypes have shown highly efficacious antinociceptive properties in acute and chronic pain models. To date, the side effects of these drugs have precluded their advancement to the clinic. This review summarizes the recent efforts to identify novel analgesics that target nAChRs, and outlines some of the key neural substrates that contribute to these physiological effects. There remain many unanswered mechanistic questions in this field, and there are still compelling reasons to explore neuronal nAChRs as targets for the relief of pain.
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Affiliation(s)
- Iboro C Umana
- Department of Anesthesia and Critical Care, University of Chicago, Chicago, IL, United States
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12
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Neuronal expression of bitter taste receptors and downstream signaling molecules in the rat brainstem. Brain Res 2012; 1475:1-10. [PMID: 22836012 DOI: 10.1016/j.brainres.2012.07.038] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 02/04/2023]
Abstract
Previous studies have shown that molecules of the taste transduction pathway may serve as biochemical markers for chemoreceptive cells in respiratory and gastrointestinal tracts. In this study, we tested the hypothesis that brainstem neurons contain signaling molecules similar to those in taste buds which may sense the chemical composition of brain extracellular fluids. We used the reverse transcription polymerase chain reaction (RT-PCR), Western blot and immunohistochemical techniques to evaluate presence of different bitter-responsive type 2 taste receptors (T2Rs), their associated G-protein α-gustducin, the downstream signaling molecules phospholipase C isoform β2 (PLC-β2) and transient receptor potential melastatin 5 (TRPM5) in the brainstem of rats. RT-PCR confirmed the mRNA coding for α-gustducin, PLC-β2, TRPM5 and rT2R1 but not that of rT2R16, rT2R26 and rT2R38 in the medulla oblongata. Western blotting confirmed the presence of α-gustducin at the protein level in rat brainstem. Immunohistochemistry identified cells expressing α-gustducin and PLC-β2 at multiple cardiorespiratory and CO(2)/H(+) chemosensory sites, including rostral ventral medulla, facial, parapyramidal, solitary tract, hypoglossal and raphe nuclei. In the medullary raphe, α-gustducin and PLC-β2 were colocalized with a subpopulation of tryptophan hydroxylase (TPH)-immunoreactive serotonergic neurons, a subset of which has respiratory CO(2)/H(+) chemosensitivity. Presence of the T2R1 gene and other genes and proteins of the bitter taste transduction pathway in the brainstem implies additional functions for taste receptors and their effector molecules apart from their gustatory function.
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Frank JG, Mendelowitz D. Synaptic and intrinsic activation of GABAergic neurons in the cardiorespiratory brainstem network. PLoS One 2012; 7:e36459. [PMID: 22570717 PMCID: PMC3343022 DOI: 10.1371/journal.pone.0036459] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 04/06/2012] [Indexed: 11/18/2022] Open
Abstract
GABAergic pathways in the brainstem play an essential role in respiratory rhythmogenesis and interactions between the respiratory and cardiovascular neuronal control networks. However, little is known about the identity and function of these GABAergic inhibitory neurons and what determines their activity. In this study we have identified a population of GABAergic neurons in the ventrolateral medulla that receive increased excitatory post-synaptic potentials during inspiration, but also have spontaneous firing in the absence of synaptic input. Using transgenic mice that express GFP under the control of the Gad1 (GAD67) gene promoter, we determined that this population of GABAergic neurons is in close apposition to cardioinhibitory parasympathetic cardiac neurons in the nucleus ambiguus (NA). These neurons fire in synchronization with inspiratory activity. Although they receive excitatory glutamatergic synaptic inputs during inspiration, this excitatory neurotransmission was not altered by blocking nicotinic receptors, and many of these GABAergic neurons continue to fire after synaptic blockade. The spontaneous firing in these GABAergic neurons was not altered by the voltage-gated calcium channel blocker cadmium chloride that blocks both neurotransmission to these neurons and voltage-gated Ca2+ currents, but spontaneous firing was diminished by riluzole, demonstrating a role of persistent sodium channels in the spontaneous firing in these cardiorespiratory GABAergic neurons that possess a pacemaker phenotype. The spontaneously firing GABAergic neurons identified in this study that increase their activity during inspiration would support respiratory rhythm generation if they acted primarily to inhibit post-inspiratory neurons and thereby release inspiration neurons to increase their activity. This population of inspiratory-modulated GABAergic neurons could also play a role in inhibiting neurons that are most active during expiration and provide a framework for respiratory sinus arrhythmia as there is an increase in heart rate during inspiration that occurs via inhibition of premotor parasympathetic cardioinhibitory neurons in the NA during inspiration.
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Affiliation(s)
- Julie G. Frank
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, United States of America
| | - David Mendelowitz
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC, United States of America
- * E-mail:
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Central respiratory effects on motor nerve activities after organophosphate exposure in a working heart brainstem preparation of the rat. Toxicol Lett 2011; 206:94-9. [PMID: 21767620 DOI: 10.1016/j.toxlet.2011.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 06/29/2011] [Accepted: 07/04/2011] [Indexed: 01/25/2023]
Abstract
The impact of organophosphorus compound (OP) intoxication on the activity of central respiratory circuitry, causing acetylcholinesterase (AChE) inhibition and accumulation of acetylcholine in the respiratory brainstem circuits, is not understood. We investigated the central effect of the OP Crotylsarin (CRS) on respiratory network activity using the working heart brainstem preparation, which specifically allows for the analysis of central drug effects without changes in brainstem oxygenation possibly caused by drug effects on peripheral cardio-respiratory activity. Respiratory network activity was determined from phrenic and hypoglossal or vagal nerve activities (PNA, HNA, VNA). To investigate combined central and peripheral CRS effects hypo-perfusion was used mimicking additional peripheral cardiovascular collapse. Systemic CRS application induced a brief central apnea and complete AChE-inhibition in the brainstem. Subsequently, respiration was characterised by highly significant reduced PNA minute activity, while HNA showed expiratory related extra bursting indicative for activation of un-specified oro-pharyngeal behaviour. During hypo-perfusion CRS induced significantly prolonged apnoea. In all experiments respiratory activity fully recovered after 1h. We conclude that CRS mediated AChE inhibition causes only transient central breathing disturbance. Apparently intrinsic brainstem mechanisms can compensate for cholinergic over activation. Nevertheless, combination of hypo-perfusion and CRS exposure evoke the characteristic breathing arrests associated with OP poisoning.
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Chiovini B, Turi GF, Katona G, Kaszás A, Erdélyi F, Szabó G, Monyer H, Csákányi A, Vizi ES, Rózsa B. Enhanced dendritic action potential backpropagation in parvalbumin-positive basket cells during sharp wave activity. Neurochem Res 2010; 35:2086-95. [PMID: 21046239 DOI: 10.1007/s11064-010-0290-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2010] [Indexed: 11/25/2022]
Abstract
In this study two-photon imaging and single cell electrophysiological measurements were carried out in PV+ hippocampal interneurons to compare the dendritic calcium dynamics of somatically evoked backpropagating action potentials (BAPs) and in vitro sharp wave oscillation (SPW) activated BAPs at different distances from the soma. In the case of 300 μm thick, non-oscillating slices, the BAP-evoked Ca(2+) (BAP-Ca(2+)) influx propagated along the dendritic tree in a non-uniform manner and its amplitude gradually reduced when measured at more distal regions. In contrast to the evoked BAP-Ca(2+)s, the spontaneous SPW-induced Ca(2+) influx had only a small distance-dependent decrement. Our results suggest that similarly to nicotinic acetylcholine receptor activation, synaptic activity during hippocampal SPWs increases AP backpropagation into distant dendritic segments. Bath application of Nimodipine, a specific Ca(2+) channel blocker and tetrodotoxine decreased the amplitude of the somatically evoked Ca(2+) influx, which suggests that L-type Ca(2+) channels play an important role both during somatically evoked and SPW-induced BAPs.
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Affiliation(s)
- Balázs Chiovini
- Institute of Experimental Medicine, Hungarian Academy of Sciences, Szigony str 43, 1083 Budapest, Hungary
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Dergacheva O, Wang X, Lovett-Barr MR, Jameson H, Mendelowitz D. The lateral paragigantocellular nucleus modulates parasympathetic cardiac neurons: a mechanism for rapid eye movement sleep-dependent changes in heart rate. J Neurophysiol 2010; 104:685-94. [PMID: 20484535 DOI: 10.1152/jn.00228.2010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rapid eye movement (REM) sleep is generally associated with a withdrawal of parasympathetic activity and heart rate increases; however, episodic vagally mediated heart rate decelerations also occur during REM sleep. This alternating pattern of autonomic activation provides a physiological basis for REM sleep-induced cardiac arrhythmias. Medullary neurons within the lateral paragigantocellular nucleus (LPGi) are thought to be active after REM sleep recovery and play a role in REM sleep control. In proximity to the LPGi are parasympathetic cardiac vagal neurons (CVNs) within the nucleus ambiguus (NA), which are critical for controlling heart rate. This study examined brain stem pathways that may mediate REM sleep-related reductions in parasympathetic cardiac activity. Electrical stimulation of the LPGi evoked inhibitory GABAergic postsynaptic currents in CVNs in an in vitro brain stem slice preparation in rats. Because brain stem cholinergic mechanisms are involved in REM sleep regulation, we also studied the role of nicotinic neurotransmission in modulation of GABAergic pathway from the LGPi to CVNs. Application of nicotine diminished the GABAergic responses evoked by electrical stimulation. This inhibitory effect of nicotine was prevented by the alpha7 nicotinic receptor antagonist alpha-bungarotoxin. Moreover, hypoxia/hypercapnia (H/H) diminished LPGi-evoked GABAergic current in CVNs, and this inhibitory effect was also prevented by alpha-bungarotoxin. In conclusion, stimulation of the LPGi evokes an inhibitory pathway to CVNs, which may constitute a mechanism for the reduced parasympathetic cardiac activity and increase in heart rate during REM sleep. Inhibition of this pathway by nicotinic receptor activation and H/H may play a role in REM sleep-related and apnea-associated bradyarrhythmias.
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Affiliation(s)
- Olga Dergacheva
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, USA.
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17
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Co-expression of nAChRs and molecules of the bitter taste transduction pathway by epithelial cells of intrapulmonary airways. Life Sci 2010; 86:281-8. [DOI: 10.1016/j.lfs.2009.12.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 12/16/2009] [Accepted: 12/28/2009] [Indexed: 11/23/2022]
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Campos M, Bravo E, Eugenín J. Respiratory dysfunctions induced by prenatal nicotine exposure. Clin Exp Pharmacol Physiol 2009; 36:1205-17. [PMID: 19473189 DOI: 10.1111/j.1440-1681.2009.05214.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. Maternal tobacco smoking is the principal risk factor associated with sudden infant death syndrome (SIDS), a leading cause of death of infants under 1 year of age. Victims of SIDS show a higher incidence of respiratory control abnormalities, including central apnoeas, delayed arousal responses and diminished ventilatory chemoreflexes. 2. Nicotine is likely the link between maternal tobacco smoking and SIDS. Prenatal nicotine exposure can alter the breathing pattern and can reduce hypoxia- and hypercarbia-induced ventilatory chemoreflexes. In vitro approaches have revealed that prenatal nicotine exposure impairs central chemosensitivity, switching the cholinergic contribution from a muscarinic to a nicotinic receptor-based drive. In addition, serotonergic, noradrenergic, GABAergic, glycinergic and glutamatergic, among others, are affected by prenatal nicotine. 3. Here we propose that prenatal nicotine affects the respiratory network through two main processes: (i) reorganization of neurotransmitter systems; and (ii) remodelling of neural circuits. These changes make breathing more vulnerable to fail in early postnatal life, which could be related to the pathogenesis of SIDS.
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Affiliation(s)
- Marlys Campos
- Laboratory of Neural Systems, Department of Biology, Universidad de Santiago, USACH, Santiago, Chile
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Dehkordi O, Rose JE, Balan KV, Kc P, Millis RM, Jayam-Trouth A. Neuroanatomical relationships of substance P-immunoreactive intrapulmonary C-fibers and nicotinic cholinergic receptors. J Neurosci Res 2009; 87:1670-8. [DOI: 10.1002/jnr.21967] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Hansen CP, Jensen AA, Christensen JK, Balle T, Liljefors T, Frølund B. Novel acetylcholine and carbamoylcholine analogues: development of a functionally selective alpha4beta2 nicotinic acetylcholine receptor agonist. J Med Chem 2009; 51:7380-95. [PMID: 18989912 DOI: 10.1021/jm701625v] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of carbamoylcholine and acetylcholine analogues were synthesized and characterized pharmacologically at neuronal nicotinic acetylcholine receptors (nAChRs). Several of the compounds displayed low nanomolar binding affinities to the alpha4beta2 nAChR and pronounced selectivity for this subtype over alpha3beta4, alpha4beta4, and alpha7 nAChRs. The high nAChR activity of carbamoylcholine analogue 5d was found to reside in its R-enantiomer, a characteristic most likely true for all other compounds in the series. Interestingly, the pronounced alpha4beta2 selectivities exhibited by some of the compounds in the binding assays translated into functional selectivity. Compound 5a was a fairly potent partial alpha4beta2 nAChR agonist with negligible activities at the alpha3beta4 and alpha7 subtypes, thus being one of the few truly functionally selective alpha4beta2 nAChR agonists published to date. Ligand-protein docking experiments using homology models of the amino-terminal domains of alpha4beta2 and alpha3beta4 nAChRs identified residues Val111(beta2)/Ile113(beta4), Phe119(beta2)/Gln121(beta4), and Thr155(alpha4)/Ser150(alpha3) as possible key determinants of the alpha4beta2/alpha3beta4-selectivity displayed by the analogues.
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Affiliation(s)
- Camilla P Hansen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, UniVersitetsparken 2, DK-2100 Copenhagen Ø, Denmark
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Kim EA, Jung KC, Sohn UD, Im C. Quantitative Structure Activity Relationship between Diazabicyclo[4.2.0]octanes Derivatives and Nicotinic Acetylcholine Receptor Agonists. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2009; 13:55-59. [PMID: 19885027 PMCID: PMC2766720 DOI: 10.4196/kjpp.2009.13.1.55] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Three dimensional quantitative structure activity relationship between diazabicyclo[4.2.0]octanes and nicotinic acetylcholine receptor (halpha4beta2 and halpha3beta4) agonists was studied using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). From 11 CoMFA and CoMSIA models, CoMSIA with steric and electrostatic fields gave the best predictive models (q(2)=0.926 and 0.945, r(2) (ncv)=0.983 and 0.988). This study can be used to develop potent halpha4beta2 receptor agonists with low activity on halpha3beta4 subtype.
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Affiliation(s)
- Eun Ae Kim
- College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
| | | | - Uy Dong Sohn
- College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
| | - Chaeuk Im
- College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea
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Frank JG, Jameson HS, Gorini C, Mendelowitz D. Mapping and identification of GABAergic neurons in transgenic mice projecting to cardiac vagal neurons in the nucleus ambiguus using photo-uncaging. J Neurophysiol 2009; 101:1755-60. [PMID: 19164103 DOI: 10.1152/jn.91134.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The neural control of heart rate is determined primarily by the activity of preganglionic parasympathetic cardiac vagal neurons (CVNs) originating in the nucleus ambiguus (NA) in the brain stem. GABAergic inputs to CVNs play an essential role in determining the activity of these neurons including a robust inhibition during each inspiratory burst. The origin of GABAergic innervation has yet to be determined however. A transgenic mouse line expressing green florescent protein (GFP) in GABAergic cells was used in conjunction with caged glutamate to identify both clusters and individual GABAergic neurons that evoke inhibitory GABAergic synaptic responses in CVNs. Transverse slices were taken with CVNs patch-clamped in the whole cell configuration. Sections containing both the pre-Botzinger complex as well as the calamus scriptorius were divided into approximately 90 quadrants, each 200 x 200 microm and were sequentially photostimulated. Inhibitory post synaptic currents (IPSCs) were recorded in CVNs after a 5-ms photostimulation of 50 microM caged glutamate. The four areas that contained GABAergic cells projecting to CVNs were 200 microm medial, 400 microm medial, 200 microm ventral, and 1,200 microm dorsal and 1,000 microm medial to patched CVNs. Once foci of GABAergic cells projecting to CVNs were determined, photostimulation of individual GABAergic neurons was conducted. The results from this study suggest that GABAergic cells located in four specific areas project to CVNs, and that these cells can be individually identified and stimulated using photouncaging to recruit GABAergic neurotransmission to CVNs.
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Affiliation(s)
- J G Frank
- Dept. of Pharmacology and Physiology, The George Washington University, 2300 I Street NW, Washington, DC 20037, USA
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