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Hamada HT, Abe Y, Takata N, Taira M, Tanaka KF, Doya K. Optogenetic activation of dorsal raphe serotonin neurons induces brain-wide activation. Nat Commun 2024; 15:4152. [PMID: 38755120 PMCID: PMC11099070 DOI: 10.1038/s41467-024-48489-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 05/01/2024] [Indexed: 05/18/2024] Open
Abstract
Serotonin is a neuromodulator that affects multiple behavioral and cognitive functions. Nonetheless, how serotonin causes such a variety of effects via brain-wide projections and various receptors remains unclear. Here we measured brain-wide responses to optogenetic stimulation of serotonin neurons in the dorsal raphe nucleus (DRN) of the male mouse brain using functional MRI with an 11.7 T scanner and a cryoprobe. Transient activation of DRN serotonin neurons caused brain-wide activation, including the medial prefrontal cortex, the striatum, and the ventral tegmental area. The same stimulation under anesthesia with isoflurane decreased brain-wide activation, including the hippocampal complex. These brain-wide response patterns can be explained by DRN serotonergic projection topography and serotonin receptor expression profiles, with enhanced weights on 5-HT1 receptors. Together, these results provide insight into the DR serotonergic system, which is consistent with recent discoveries of its functions in adaptive behaviors.
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Affiliation(s)
- Hiro Taiyo Hamada
- Neural Computation Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
- Research & Development Department, Araya Inc, Tokyo, Japan.
| | - Yoshifumi Abe
- Division of Brain Sciences, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan
| | - Norio Takata
- Division of Brain Sciences, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan
| | - Masakazu Taira
- Neural Computation Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Kenji F Tanaka
- Division of Brain Sciences, Institute for Advanced Medical Research, Keio University School of Medicine, Tokyo, Japan
| | - Kenji Doya
- Neural Computation Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
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2
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Turk AZ, Millwater M, SheikhBahaei S. Whole-brain analysis of CO 2 chemosensitive regions and identification of the retrotrapezoid and medullary raphé nuclei in the common marmoset ( Callithrix jacchus). BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.26.558361. [PMID: 37986845 PMCID: PMC10659419 DOI: 10.1101/2023.09.26.558361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Respiratory chemosensitivity is an important mechanism by which the brain senses changes in blood partial pressure of CO2 (PCO2). It is proposed that special neurons (and astrocytes) in various brainstem regions play key roles as CO2 central respiratory chemosensors in rodents. Although common marmosets (Callithrix jacchus), New-World non-human primates, show similar respiratory responses to elevated inspired CO2 as rodents, the chemosensitive regions in marmoset brain have not been defined yet. Here, we used c-fos immunostainings to identify brain-wide CO2-activated brain regions in common marmosets. In addition, we mapped the location of the retrotrapezoid nucleus (RTN) and raphé nuclei in the marmoset brainstem based on colocalization of CO2-induced c-fos immunoreactivity with Phox2b, and TPH immunostaining, respectively. Our data also indicated that, similar to rodents, marmoset RTN astrocytes express Phox2b and have complex processes that create a meshwork structure at the ventral surface of medulla. Our data highlight some cellular and structural regional similarities in brainstem of the common marmosets and rodents.
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Affiliation(s)
- Ariana Z. Turk
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Marissa Millwater
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
| | - Shahriar SheikhBahaei
- Neuron-Glia Signaling and Circuits Unit, National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health (NIH), Bethesda, 20892 MD, USA
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3
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Gonye EC, Bayliss DA. Criteria for central respiratory chemoreceptors: experimental evidence supporting current candidate cell groups. Front Physiol 2023; 14:1241662. [PMID: 37719465 PMCID: PMC10502317 DOI: 10.3389/fphys.2023.1241662] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023] Open
Abstract
An interoceptive homeostatic system monitors levels of CO2/H+ and provides a proportionate drive to respiratory control networks that adjust lung ventilation to maintain physiologically appropriate levels of CO2 and rapidly regulate tissue acid-base balance. It has long been suspected that the sensory cells responsible for the major CNS contribution to this so-called respiratory CO2/H+ chemoreception are located in the brainstem-but there is still substantial debate in the field as to which specific cells subserve the sensory function. Indeed, at the present time, several cell types have been championed as potential respiratory chemoreceptors, including neurons and astrocytes. In this review, we advance a set of criteria that are necessary and sufficient for definitive acceptance of any cell type as a respiratory chemoreceptor. We examine the extant evidence supporting consideration of the different putative chemoreceptor candidate cell types in the context of these criteria and also note for each where the criteria have not yet been fulfilled. By enumerating these specific criteria we hope to provide a useful heuristic that can be employed both to evaluate the various existing respiratory chemoreceptor candidates, and also to focus effort on specific experimental tests that can satisfy the remaining requirements for definitive acceptance.
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Affiliation(s)
- Elizabeth C. Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA, United States
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4
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Lusk SJ, McKinney A, Hunt PJ, Fahey PG, Patel J, Chang A, Sun JJ, Martinez VK, Zhu PJ, Egbert JR, Allen G, Jiang X, Arenkiel BR, Tolias AS, Costa-Mattioli M, Ray RS. A CRISPR toolbox for generating intersectional genetic mouse models for functional, molecular, and anatomical circuit mapping. BMC Biol 2022; 20:28. [PMID: 35086530 PMCID: PMC8796356 DOI: 10.1186/s12915-022-01227-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 01/06/2022] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND The functional understanding of genetic interaction networks and cellular mechanisms governing health and disease requires the dissection, and multifaceted study, of discrete cell subtypes in developing and adult animal models. Recombinase-driven expression of transgenic effector alleles represents a significant and powerful approach to delineate cell populations for functional, molecular, and anatomical studies. In addition to single recombinase systems, the expression of two recombinases in distinct, but partially overlapping, populations allows for more defined target expression. Although the application of this method is becoming increasingly popular, its experimental implementation has been broadly restricted to manipulations of a limited set of common alleles that are often commercially produced at great expense, with costs and technical challenges associated with production of intersectional mouse lines hindering customized approaches to many researchers. Here, we present a simplified CRISPR toolkit for rapid, inexpensive, and facile intersectional allele production. RESULTS Briefly, we produced 7 intersectional mouse lines using a dual recombinase system, one mouse line with a single recombinase system, and three embryonic stem (ES) cell lines that are designed to study the way functional, molecular, and anatomical features relate to each other in building circuits that underlie physiology and behavior. As a proof-of-principle, we applied three of these lines to different neuronal populations for anatomical mapping and functional in vivo investigation of respiratory control. We also generated a mouse line with a single recombinase-responsive allele that controls the expression of the calcium sensor Twitch-2B. This mouse line was applied globally to study the effects of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) on calcium release in the ovarian follicle. CONCLUSIONS The lines presented here are representative examples of outcomes possible with the successful application of our genetic toolkit for the facile development of diverse, modifiable animal models. This toolkit will allow labs to create single or dual recombinase effector lines easily for any cell population or subpopulation of interest when paired with the appropriate Cre and FLP recombinase mouse lines or viral vectors. We have made our tools and derivative intersectional mouse and ES cell lines openly available for non-commercial use through publicly curated repositories for plasmid DNA, ES cells, and transgenic mouse lines.
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Affiliation(s)
- Savannah J Lusk
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Andrew McKinney
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Patrick J Hunt
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Paul G Fahey
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Jay Patel
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Andersen Chang
- Department of Statistics, Rice University, Houston, TX, USA
| | - Jenny J Sun
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Vena K Martinez
- Department of Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Ping Jun Zhu
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Jeremy R Egbert
- Department of Cell Biology, University of Connecticut, Farmington, CT, USA
| | - Genevera Allen
- Department of Statistics, Computer Science, and Electrical and Computer Engineering, Rice University, Houston, TX, USA
- Neurological Research Institute, Baylor College of Medicine, Houston, TX, USA
| | - Xiaolong Jiang
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Benjamin R Arenkiel
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
- McNair Medical Institute, Houston, TX, USA
| | - Andreas S Tolias
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | | | - Russell S Ray
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- McNair Medical Institute, Houston, TX, USA.
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5
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Abuin-Martínez C, Vidal R, Gutiérrez-López MD, Pérez-Hernández M, Giménez-Gómez P, Morales-Puerto N, O'Shea E, Colado MI. Increased kynurenine concentration attenuates serotonergic neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in rats through activation of aryl hydrocarbon receptor. Neuropharmacology 2021; 187:108490. [PMID: 33607146 DOI: 10.1016/j.neuropharm.2021.108490] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 01/15/2021] [Accepted: 02/02/2021] [Indexed: 01/08/2023]
Abstract
3,4-Methylenedioxymethamphetamine (MDMA) is an amphetamine derivative that has been shown to produce serotonergic damage in the brains of primates, including humans, and of rats. Tryptophan, the precursor of serotonin, is primarily degraded through the kynurenine (KYN) pathway, producing among others KYN, the main metabolite of this route. KYN has been reported as an endogenous agonist of the aryl hydrocarbon receptor (AhR), a transcription factor involved in several neurological functions. This study aims to determine the effect of MDMA on the KYN pathway and on AhR activity and to establish their role in the long-term serotonergic neurotoxicity induced by the drug in rats. Our results show that MDMA induces the activation of the KYN pathway, mediated by hepatic tryptophan 2,3-dioxygenase (TDO). MDMA also activated AhR as evidenced by increased AhR nuclear translocation and CYP1B1 mRNA expression. Autoradiographic quantification of serotonin transporters showed that both the TDO inhibitor 680C91 and the AhR antagonist CH-223191 potentiated the neurotoxicity induced by MDMA, while administration of exogenous l-kynurenine or of the AhR positive modulator 3,3'-diindolylmethane (DIM) partially prevented the serotonergic damage induced by the drug. The results demonstrate for the first time that MDMA increases KYN levels and AhR activity, and these changes appear to play a role in limiting the neurotoxicity induced by the drug. This work provides a better understanding of the physiological mechanisms that attenuate the brain damage induced by MDMA and identify modulation of the KYN pathway and of AhR as potential therapeutic strategies to limit the negative effects of MDMA.
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Affiliation(s)
- C Abuin-Martínez
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - R Vidal
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - M D Gutiérrez-López
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - M Pérez-Hernández
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - P Giménez-Gómez
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - N Morales-Puerto
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain
| | - E O'Shea
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain.
| | - M I Colado
- Departamento de Farmacología y Toxicología, Facultad de Medicina, Universidad Complutense, Pza. Ramón y Cajal s/n, 28040, Madrid, Spain; Instituto de Investigación Sanitaria Hospital 12 de Octubre, Madrid, Spain; Red de Trastornos Adictivos, Instituto de Salud Carlos III, Madrid, Spain; Instituto Universitario de Investigación Neuroquímica (IUIN), Universidad Complutense, Madrid, Spain.
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6
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Leirão IP, Colombari DSA, da Silva GSF, Zoccal DB. Lesion of Serotonergic Afferents to the Retrotrapezoid Nucleus Impairs the Tachypneic Response to Hypercapnia in Unanesthetized Animals. Neuroscience 2020; 452:63-77. [PMID: 33212216 DOI: 10.1016/j.neuroscience.2020.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 10/30/2020] [Accepted: 11/03/2020] [Indexed: 12/17/2022]
Abstract
Hypercapnia promotes an increase in pulmonary ventilation due to the stimulation of brainstem chemosensory cells that are connected to the respiratory network. Among these cells are the raphe serotonergic neurons which widely send projections to distinct central respiratory compartments. Nevertheless, the physiological role of specific raphe serotonergic projections to other chemosensitive sites on the emergence of hypercapnia ventilatory response in vivo still remains to be elucidated. Here we investigated whether the ventilatory response to hypercapnia requires serotonergic inputs to the chemosensitive cells of the retrotrapezoid nucleus (RTN) in the ventrolateral medulla. To test this, pulmonary ventilation was evaluated under baseline conditions and during hypercapnia (7% CO2) in unanesthetized juvenile Holtzman rats (60-90 g) that received bilateral microinjections of either vehicle (control) or anti-SERT-SAP (0.1 mM, 10 pmol/100 nl) toxin in the RTN to retrogradely destroy serotonergic afferents to this region. Fifteen days after microinjections, baseline ventilation was not different between anti-SERT-SAP (n = 8) and control animals (n = 9). In contrast, the ablation of RTN-projecting serotonergic neurons markedly attenuated the hypercapnia-induced increase in respiratory frequency which was correlated with reduced numbers of serotonergic neurons in the raphe obscurus and magnus, but not in the raphe pallidus. The increase in tidal volume during hypercapnia was not significantly affected by anti-SERT-SAP microinjections in the RTN. Our data indicate that serotoninergic neurons that send projections to the RTN region are required for the processing of ventilatory reflex response during exposure to high CO2 in unanesthetized conditions.
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Affiliation(s)
- Isabela P Leirão
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Débora S A Colombari
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Glauber S F da Silva
- Department of Physiology and Biophysics. Institute of Biological Sciences, Federal University of Minas Gerais (ICB/UFMG), Belo Horizonte, MG, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, SP, Brazil.
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7
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Xu W, Wang L, Yuan XS, Wang TX, Li WX, Qu WM, Hong ZY, Huang ZL. Sevoflurane depresses neurons in the medial parabrachial nucleus by potentiating postsynaptic GABA A receptors and background potassium channels. Neuropharmacology 2020; 181:108249. [PMID: 32931816 DOI: 10.1016/j.neuropharm.2020.108249] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2020] [Revised: 06/23/2020] [Accepted: 07/20/2020] [Indexed: 12/28/2022]
Abstract
Despite persistent clinical use for over 170 years, the neuronal mechanisms by which general anesthetics produce hypnosis remain unclear. Previous studies suggest that anesthetics exert hypnotic effects by acting on endogenous arousal circuits. Recently, it has been shown that the medial parabrachial nucleus (MPB) is a novel wake-promoting component in the dorsolateral pons. However, it is not known whether and how the MPB contributes to anesthetic-induced hypnosis. Here, we investigated the action of sevoflurane, a widely used volatile anesthetic agent that best represents the drug class of halogenated ethers, on MPB neurons in mice. Using in vivo fiber photometry, we found that the population activities of MPB neurons were inhibited during sevoflurane-induced loss of consciousness. Using in vitro whole-cell patch-clamp recordings, we revealed that sevoflurane suppressed the firing rate of MPB neurons in concentration-dependent and reversible manners. At a concentration equal to MAC of hypnosis, sevoflurane potentiated synaptic GABAA receptors (GABAA-Rs), and the inhibitory effect of sevoflurane on the firing rate of MPB neurons was completely abolished by picrotoxin, which is a selective GABAA-R antagonist. At a concentration equivalent to MAC of immobility, sevoflurane directly hyperpolarized MPB neurons and induced a significant decrease in membrane input resistance by increasing a basal potassium conductance. Moreover, pharmacological blockade of GABAA-Rs in the MPB prolongs induction and shortens emergence under sevoflurane inhalation at MAC of hypnosis. These results indicate that sevoflurane inhibits MPB neurons through postsynaptic GABAA-Rs and background potassium channels, which contributes to sevoflurane-induced hypnosis.
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Affiliation(s)
- Wei Xu
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Lu Wang
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Xiang-Shan Yuan
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Tian-Xiao Wang
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Wen-Xian Li
- Department of Anesthesiology, The Eye, Ear, Nose and Throat Hospital of Fudan University, Shanghai Medical College of Fudan University, Shanghai, China
| | - Wei-Min Qu
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China
| | - Zong-Yuan Hong
- Laboratory of Quantitative Pharmacology, Department of Pharmacology, Wannan Medical College, Wuhu, China
| | - Zhi-Li Huang
- Department of Pharmacology, School of Basic Medical Sciences; State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, and Institutes of Brain Science, Shanghai Medical College of Fudan University, Shanghai, China.
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8
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Leirão IP, Zoccal DB, Gargaglioni LH, da Silva GSF. Differential modulation of active expiration during hypercapnia by the medullary raphe in unanesthetized rats. Pflugers Arch 2020; 472:1563-1576. [PMID: 32914212 DOI: 10.1007/s00424-020-02455-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 07/30/2020] [Accepted: 08/27/2020] [Indexed: 11/26/2022]
Abstract
Active expiration represents an important mechanism to improve ventilation in conditions of augmented ventilatory demand, such as hypercapnia. While a rostral ventromedullary region, the parafacial respiratory group (pFRG), has been identified as a conditional expiratory oscillator, little is known about how central chemosensitive sites contribute to modulate active expiration under hypercapnia. In this study, we investigated the influence of the medullary raphe in the emergence of phasic expiratory abdominal activity during hypercapnia in unanesthetized adult male rats, in a state-dependent manner. To do so, reverse microdialysis of muscimol (GABAA receptor agonist, 1 mM) or 8-OH-DPAT (5-HT1A agonist, 1 mM) was applied in the MR during sleep and wakefulness periods, both in normocapnic (room air) and hypercapnic conditions (7% CO2). Electromyography (EMG) of diaphragm and abdominal muscles was performed to measure inspiratory and expiratory motor outputs. We found that active expiration did not occur in room air exposure during wakefulness or sleep. However, hypercapnia did recruit active expiration, and differential effects were observed with the drug dialyses in the medullary raphe. Muscimol increased the diaphragm inspiratory motor output and also increased the amplitude and frequency of abdominal expiratory rhythmic activity during hypercapnia in wakefulness periods. On the other hand, the microdialysis of 8-OH-DPAT attenuated hypercapnia-induced active expiration in a state-dependent manner. Our data suggest that the medullary raphe can either inhibit or potentiate respiratory motor activity during hypercapnia, and the balance of these inhibitory or excitatory outputs may determine the expression of active expiration.
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Affiliation(s)
- Isabela P Leirão
- Department of Physiology and Pathology, School of Dentistry of Araraquara (FOAR), São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry of Araraquara (FOAR), São Paulo State University (UNESP), Araraquara, SP, Brazil
| | - Luciane H Gargaglioni
- Department of Animal Morphology and Physiology, College of Agricultural and Veterinary Sciences, São Paulo State University (FCAV-UNESP), Jaboticabal, SP, Brazil
| | - Glauber S F da Silva
- Department of Physiology and Biophysics. Institute of Biological Sciences, Federal University of Minas Gerais (ICB/UFMG), Belo Horizonte, MG, Brazil.
- Departamento de Fisiologia e Biofísica, ICB/UFMG, Avenida Presidente Antônio Carlos, 6627, Campus UFMG, Belo Horizonte, MG, 31270-901, Brazil.
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9
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Ou M, Kuo FS, Chen X, Kahanovitch U, Olsen ML, Du G, Mulkey DK. Isoflurane inhibits a Kir4.1/5.1-like conductance in neonatal rat brainstem astrocytes and recombinant Kir4.1/5.1 channels in a heterologous expression system. J Neurophysiol 2020; 124:740-749. [PMID: 32727273 PMCID: PMC7509298 DOI: 10.1152/jn.00358.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 02/08/2023] Open
Abstract
All inhalation anesthetics used clinically including isoflurane can suppress breathing; since this unwanted side effect can persist during the postoperative period and complicate patient recovery, there is a need to better understand how isoflurane affects cellular and molecular elements of respiratory control. Considering that astrocytes in a brainstem region known as the retrotrapezoid nucleus (RTN) contribute to the regulation of breathing in response to changes in CO2/H+ (i.e., function as respiratory chemoreceptors), and astrocytes in other brain regions are highly sensitive to isoflurane, we wanted to determine whether and how RTN astrocytes respond to isoflurane. We found that RTN astrocytes in slices from neonatal rat pups (7-12 days postnatal) respond to clinically relevant levels of isoflurane by inhibition of a CO2/H+-sensitive Kir4.1/5.1-like conductance [50% effective concentration (EC50) = 0.8 mM or ~1.7%]. We went on to confirm that similar levels of isoflurane (EC50 = 0.53 mM or 1.1%) inhibit recombinant Kir4.1/5.1 channels but not homomeric Kir4.1 channels expressed in HEK293 cells. We also found that exposure to CO2/H+ occluded subsequent effects of isoflurane on both native and recombinant Kir4.1/5.1 currents. These results identify Kir4.1/5.1 channels in astrocytes as novel targets of isoflurane. These results suggest astrocyte Kir4.1/5.1 channels contribute to certain aspects of general anesthesia including altered respiratory control.NEW & NOTEWORTHY An unwanted side effect of isoflurane anesthesia is suppression of breathing. Despite this clinical significance, effects of isoflurane on cellular and molecular elements of respiratory control are not well understood. Here, we show that isoflurane inhibits heteromeric Kir4.1/5.1 channels in a mammalian expression system and a Kir4.1/5.1-like conductance in astrocytes in a brainstem respiratory center. These results identify astrocyte Kir4.1/5.1 channels as novel targets of isoflurane and potential substrates for altered respiratory control during isoflurane anesthesia.
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Affiliation(s)
- Mengchan Ou
- Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu City, China
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Fu-Shan Kuo
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Xinnian Chen
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
| | - Uri Kahanovitch
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Michelle L Olsen
- School of Neuroscience, Virginia Polytechnic and State University, Blacksburg, Virginia
| | - Guizhi Du
- Department of Anesthesiology, West China Hospital, Sichuan University, Chengdu City, China
| | - Daniel K Mulkey
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut
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10
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Avraam J, Wu Y, Richerson GB. Perinatal Nicotine Reduces Chemosensitivity of Medullary 5-HT Neurons after Maturation in Culture. Neuroscience 2020; 446:80-93. [PMID: 32818601 DOI: 10.1016/j.neuroscience.2020.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 08/07/2020] [Accepted: 08/10/2020] [Indexed: 01/19/2023]
Abstract
Perinatal exposure to nicotine produces ventilatory and chemoreflex deficits in neonatal mammals. Medullary 5-HT neurons are putative central chemoreceptors that innervate respiratory nuclei and promote ventilation, receive cholinergic input and express nicotinic acetylcholine receptors (nAChRs). Perforated patch clamp recordings were made from cultured 5-HT neurons dissociated from the medullary raphé of 0-3 day old mice expressing enhanced yellow fluorescent protein driven by the enhancer region for PET1 (ePet-EYFP). The effect of exposure to low (6 mg kg-1day-1) or high (60 mg kg-1day-1) doses of nicotine in utero (prenatal), in culture (postnatal), or both and the effect of acute nicotine exposure (10 μM), were examined on baseline firing rate (FR at 5% CO2, pH = 7.4) and the change in FR with acidosis (9% CO2, pH 7.2) in young (12-21 days in vitro, DIV) and older (≥22 DIV) acidosis stimulated 5-HT neurons. Nicotine exposed neurons exhibited ∼67% of the response to acidosis recorded in neurons given vehicle (p = 0.005), with older neurons exposed to high dose prenatal and postnatal nicotine, exhibiting only 28% of that recorded in the vehicle neurons (p < 0.01). In neurons exposed to low or high dose prenatal and postnatal nicotine, acute nicotine exposure led to a smaller increase in FR (∼+51% vs +168%, p = 0.026) and response to acidosis (+6% vs +67%, p = 0.014) compared to vehicle. These data show that exposure to nicotine during development reduces chemosensitivity of 5-HT neurons as they mature, an effect that may be related to the abnormal chemoreflexes reported in rodents exposed to nicotine in utero, and may cause a greater risk for sudden infant death syndrome (SIDS).
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Affiliation(s)
- Joanne Avraam
- Department of Neurology, University of Iowa, Iowa City, IA 52242, United States; Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Yuanming Wu
- Department of Neurology, University of Iowa, Iowa City, IA 52242, United States
| | - George Bradley Richerson
- Department of Neurology, University of Iowa, Iowa City, IA 52242, United States; Veteran's Affairs Medical Center, Iowa City, IA 52242, United States; Department of Molecular Physiology & Biophysics, University of Iowa, Iowa City, IA 52242, United States; Iowa Neuroscience Institute, University of Iowa, Iowa City, IA 52242, United States.
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11
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5-HT neurons and central CO2 chemoreception. ACTA ACUST UNITED AC 2020. [DOI: 10.1016/b978-0-444-64125-0.00021-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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12
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Levigoureux E, Vidal B, Fieux S, Bouillot C, Emery S, Newman-Tancredi A, Zimmer L. Serotonin 5-HT 1A Receptor Biased Agonists Induce Different Cerebral Metabolic Responses: A [ 18F]-Fluorodesoxyglucose Positron Emission Tomography Study in Conscious and Anesthetized Rats. ACS Chem Neurosci 2019; 10:3108-3119. [PMID: 30576601 DOI: 10.1021/acschemneuro.8b00584] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Serotonin 5-HT1A receptors constitute an attractive therapeutic target for various psychiatric or neurodegenerative disorders. These receptors are expressed in multiple brain regions on different neuronal populations and can be coupled with distinct G-protein subtypes; such functional diversity complicates the use of 5-HT1A ligands in several pathologies where it would be desirable to stimulate the receptors in a precise region. Therefore, using "biased agonists" able to target specifically certain subpopulations of 5-HT1A receptors would enable achievement of better therapeutic benefit. Several 5-HT1A receptor biased agonists are currently in development, including NLX-101 (aka F15599) and NLX-112 (aka F13640, befiradol), with preclinical data suggesting that they preferentially target different populations of 5-HT1A receptors. However, most previous studies used invasive and regionally limited approaches. In this context, [18F]-fluorodesoxyglucose (FDG)-positron emission tomography (PET) imaging constitutes an interesting technique as it enables noninvasive mapping of the regional brain activity changes following a pharmacological challenge in conscious animals. We report here the evaluation of cerebral glucose metabolism following intraperitoneal injection of different doses of NLX-112 or NLX-101 in conscious or isoflurane-anesthetized rats. The biased agonists produced different metabolic "fingerprints" with distinct regional preferences, consistent with previous studies. At equal doses, the effect of NLX-101 was less marked than NLX-112 in the piriform cortex, in the striatum (in terms of inhibition), and in the pontine nuclei and the cerebellum (in terms of activation); furthermore, only NLX-112 increased the glucose metabolism in the parietal cortex, whereas only NLX-101 induced a clear activation in the colliculi and the frontal cortex, which may be related to its distinctive procognitive profile. Both agonist effects were almost completely unapparent in anesthetized animals, underlining the importance of studying serotonergic neurotransmission in the conscious state. In this regard, [18F]FDG-PET imaging seems very complementary with other functional imaging techniques such as pharmacological MRI.
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Affiliation(s)
- Elise Levigoureux
- Université de Lyon, Université Claude Bernard Lyon 1, Lyon Neuroscience Research Center, CNRS UMR5292, INSERM U1028, Lyon 69677, France
- Hospices Civils de Lyon, Lyon 69677, France
| | - Benjamin Vidal
- Université de Lyon, Université Claude Bernard Lyon 1, Lyon Neuroscience Research Center, CNRS UMR5292, INSERM U1028, Lyon 69677, France
| | - Sylvain Fieux
- Université de Lyon, Université Claude Bernard Lyon 1, Lyon Neuroscience Research Center, CNRS UMR5292, INSERM U1028, Lyon 69677, France
| | | | - Stéphane Emery
- Université de Lyon, Université Claude Bernard Lyon 1, Lyon Neuroscience Research Center, CNRS UMR5292, INSERM U1028, Lyon 69677, France
- Hospices Civils de Lyon, Lyon 69677, France
| | | | - Luc Zimmer
- Université de Lyon, Université Claude Bernard Lyon 1, Lyon Neuroscience Research Center, CNRS UMR5292, INSERM U1028, Lyon 69677, France
- Hospices Civils de Lyon, Lyon 69677, France
- CERMEP-Imaging Platform, Bron 69677, France
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13
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Lu L, Fu X, Liew Y, Zhang Y, Zhao S, Xu Z, Zhao J, Li D, Li Q, Stanley GB, Duan X. Soft and MRI Compatible Neural Electrodes from Carbon Nanotube Fibers. NANO LETTERS 2019; 19:1577-1586. [PMID: 30798604 DOI: 10.1021/acs.nanolett.8b04456] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Soft and magnetic resonance imaging (MRI) compatible neural electrodes enable stable chronic electrophysiological measurements and anatomical or functional MRI studies of the entire brain without electrode interference with MRI images. These properties are important for many studies, ranging from a fundamental neurophysiological study of functional MRI signals to a chronic neuromodulatory effect investigation of therapeutic deep brain stimulation. Here we develop soft and MRI compatible neural electrodes using carbon nanotube (CNT) fibers with a diameter from 20 μm down to 5 μm. The CNT fiber electrodes demonstrate excellent interfacial electrochemical properties and greatly reduced MRI artifacts than PtIr electrodes under a 7.0 T MRI scanner. With a shuttle-assisted implantation strategy, we show that the soft CNT fiber electrodes can precisely target specific brain regions and record high-quality single-unit neural signals. Significantly, they are capable of continuously detecting and isolating single neuronal units from rats for up to 4-5 months without electrode repositioning, with greatly reduced brain inflammatory responses as compared to their stiff metal counterparts. In addition, we show that due to their high tensile strength, the CNT fiber electrodes can be retracted controllably postinsertion, which provides an effective and convenient way to do multidepth recording or potentially selecting cells with particular response properties. The chronic recording stability and MRI compatibility, together with their small size, provide the CNT fiber electrodes unique research capabilities for both basic and applied neuroscience studies.
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Affiliation(s)
- Linlin Lu
- Department of Biomedical Engineering, College of Engineering , Peking University , Beijing 100871 , China
- Wallace H. Coulter Department of Biomedical Engineering , Georgia Institute of Technology and Emory University , Atlanta , Georgia 30332 , United States
| | - Xuefeng Fu
- Department of Biomedical Engineering, College of Engineering , Peking University , Beijing 100871 , China
| | - Yijuin Liew
- Wallace H. Coulter Department of Biomedical Engineering , Georgia Institute of Technology and Emory University , Atlanta , Georgia 30332 , United States
| | - Yongyi Zhang
- Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences , Suzhou 215123 , China
| | - Siyuan Zhao
- Department of Biomedical Engineering, College of Engineering , Peking University , Beijing 100871 , China
- Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
| | - Zheng Xu
- Department of Biomedical Engineering, College of Engineering , Peking University , Beijing 100871 , China
| | - Jingna Zhao
- Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences , Suzhou 215123 , China
| | - Da Li
- Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences , Suzhou 215123 , China
| | - Qingwen Li
- Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences , Suzhou 215123 , China
| | - Garrett B Stanley
- Wallace H. Coulter Department of Biomedical Engineering , Georgia Institute of Technology and Emory University , Atlanta , Georgia 30332 , United States
| | - Xiaojie Duan
- Department of Biomedical Engineering, College of Engineering , Peking University , Beijing 100871 , China
- Academy for Advanced Interdisciplinary Studies , Peking University , Beijing 100871 , China
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14
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Loeven AM, Receno CN, Cunningham CM, DeRuisseau LR. Arterial blood sampling in male CD-1 and C57BL/6J mice with 1% isoflurane is similar to awake mice. J Appl Physiol (1985) 2018; 125:1749-1759. [PMID: 30284518 PMCID: PMC6737457 DOI: 10.1152/japplphysiol.00640.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Isoflurane (ISO) is a commonly used anesthetic that offers rapid recovery for laboratory animal research. Initial studies indicated no difference in arterial Pco2 (PaCO2) or pH between conscious (NO ISO) and 1% ISO-exposed CD-1 mice. Our laboratory investigated whether arterial blood sampling with 1% ISO is a suitable alternative to NO ISO sampling for monitoring ventilation in a commonly studied mouse strain. We hypothesized similar blood chemistry, breathing patterns, and cardiovascular responses with NO ISO and 1% ISO. C57BL/6J mice underwent unrestrained barometric plethysmography to quantify the pattern of breathing. Mice exposed to hypoxic and hypercapnic gas under 1% ISO displayed blunted responses; with air, there were no breathing differences. Blood pressure and heart rate were not different between NO ISO and 1% ISO-exposed mice breathing air. Oxygen saturation was not different between groups receiving 2% ISO, 1% ISO, or air. Breathing frequency stabilized at ~11 min of 1% ISO following 2% ISO exposure, suggesting that 11 min is the optimal time for a sample in C57BL/6J mice. Blood samples at 1% ISO and NO ISO revealed no differences in blood pH and PaCO2 in C57BL/6J mice. Overall, this method reveals similar arterial blood sampling values in awake and 1% ISO CD-1 and C57BL/6J mice exposed to air. Although this protocol may be appropriate in other mouse strains when a conscious sample is not feasible, caution is warranted first to identify breathing frequency responses at 1% ISO to tailor the protocol. NEW & NOTEWORTHY Conscious arterial blood sampling is influenced by extraneous factors and is a challenging method due to the small size of mice. Through a series of experiments, we show that arterial blood sampling with 1% isoflurane (ISO) is an alternative to awake sampling in C57BL/6J and CD-1 male mice breathing air. Monitoring breathing frequency during 1% ISO is important to the protocol and should be closely followed to confirm adequate recovery after the catheter implantation.
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Affiliation(s)
- Ashley M Loeven
- Department of Biological and Environmental Sciences, Le Moyne College , Syracuse, New York
| | - Candace N Receno
- Department of Biological and Environmental Sciences, Le Moyne College , Syracuse, New York
| | - Caitlin M Cunningham
- Department of Mathematics, Statistics and Computer Science, Le Moyne College , Syracuse, New York
| | - Lara R DeRuisseau
- Department of Biological and Environmental Sciences, Le Moyne College , Syracuse, New York
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15
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In vivo biased agonism at 5-HT 1A receptors: characterisation by simultaneous PET/MR imaging. Neuropsychopharmacology 2018; 43:2310-2319. [PMID: 30030540 PMCID: PMC6135772 DOI: 10.1038/s41386-018-0145-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 06/07/2018] [Accepted: 06/27/2018] [Indexed: 12/26/2022]
Abstract
In neuropharmacology, the recent concept of 'biased agonism' denotes the capacity of certain agonists to target-specific intracellular pathways of a given receptor in specific brain areas. In the context of serotonin pharmacotherapy, 5-HT1A receptor-biased agonists could be of great interest in several neuropsychiatric disorders. The aim of this study was to determine whether biased agonists could be differentiated in terms of regional targeting by use of simultaneous functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) brain imaging. We compared two 5-HT1A-biased agonists, NLX-112 and NLX-101, injected at three different doses in anaesthetised cats (n = 4). PET imaging was acquired for 90 min after bolus administration followed by constant infusion of the 5-HT1A radiotracer, [18F]MPPF. Drug occupancy was evaluated after injection at 50 min and BOLD fMRI was simultaneously acquired to evaluate subsequent brain activation patterns. 5-HT1A receptor occupancy was found to be dose-dependent for both agonists, but differed in magnitude and spatial distribution at equal doses with distinct BOLD patterns. Functional connectivity, as measured by BOLD signal temporal correlations between regions, was also differently modified by NLX-112 or NLX-101. Voxel-based correlation analyses between PET and fMRI suggested that NLX-112 stimulates both 5-HT1A autoreceptors and post-synaptic receptors, whereas NLX-101 preferentially stimulates post-synaptic cortical receptors. In cingulate cortex, the agonists induced opposite BOLD signal changes in response to receptor occupancy. These data constitute the first simultaneous exploration of 5-HT1A occupancy and its consequences in terms of brain activation, and demonstrates differential signalling by two 5-HT1A-biased agonists. Combined PET/fMRI represents a powerful tool in neuropharmacology, and opens new ways to address the concept of biased agonism by translational approaches.
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16
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Boffi JC, Knabbe J, Kaiser M, Kuner T. KCC2-dependent Steady-state Intracellular Chloride Concentration and pH in Cortical Layer 2/3 Neurons of Anesthetized and Awake Mice. Front Cell Neurosci 2018; 12:7. [PMID: 29422838 PMCID: PMC5788967 DOI: 10.3389/fncel.2018.00007] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 01/05/2018] [Indexed: 12/31/2022] Open
Abstract
Neuronal intracellular Cl− concentration ([Cl−]i) influences a wide range of processes such as neuronal inhibition, membrane potential dynamics, intracellular pH (pHi) or cell volume. Up to date, neuronal [Cl−]i has predominantly been studied in model systems of reduced complexity. Here, we implemented the genetically encoded ratiometric Cl− indicator Superclomeleon (SCLM) to estimate the steady-state [Cl−]i in cortical neurons from anesthetized and awake mice using 2-photon microscopy. Additionally, we implemented superecliptic pHluorin (SE-pHluorin) as a ratiometric sensor to estimate the intracellular steady-state pH (pHi) of mouse cortical neurons in vivo. We estimated an average resting [Cl−]i of 6 ± 2 mM with no evidence of subcellular gradients in the proximal somato-dendritic domain and an average somatic pHi of 7.1 ± 0.2. Neither [Cl−]i nor pHi were affected by isoflurane anesthesia. We deleted the cation-Cl− co-transporter KCC2 in single identified neurons of adult mice and found an increase of [Cl−]i to approximately 26 ± 8 mM, demonstrating that under in vivo conditions KCC2 produces low [Cl−]i in adult mouse neurons. In summary, neurons of the brain of awake adult mice exhibit a low and evenly distributed [Cl−]i in the proximal somato-dendritic compartment that is independent of anesthesia and requires KCC2 expression for its maintenance.
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Affiliation(s)
- Juan C Boffi
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Johannes Knabbe
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Michaela Kaiser
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
| | - Thomas Kuner
- Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, University of Heidelberg, Heidelberg, Germany
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17
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Raphe Pallidus is Not Important to Central Chemoreception in a Rat Model of Parkinson’s Disease. Neuroscience 2018; 369:350-362. [DOI: 10.1016/j.neuroscience.2017.11.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 11/20/2017] [Accepted: 11/21/2017] [Indexed: 01/31/2023]
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18
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Massey CA, Richerson GB. Isoflurane, ketamine-xylazine, and urethane markedly alter breathing even at subtherapeutic doses. J Neurophysiol 2017; 118:2389-2401. [PMID: 28747467 DOI: 10.1152/jn.00350.2017] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/19/2017] [Accepted: 07/20/2017] [Indexed: 11/22/2022] Open
Abstract
Anesthetics are widely used for animal research on respiratory control in vivo, but their effect on breathing and CO2 chemoreception has not been well characterized in mice, a species now often used for these studies. We previously demonstrated that 1% isoflurane markedly reduces the hypercapnic ventilatory response (HCVR) in adult mice in vivo and masks serotonin [5-hydroxytryptamine (5-HT)] neuron chemosensitivity in vitro. Here we investigated effects of 0.5% isoflurane on breathing in adult mice and also found a large reduction in the HCVR even at this subanesthetic concentration. We then tested the effects on breathing of ketamine-xylazine and urethane, anesthetics widely used in research on breathing. We found that these agents altered baseline breathing and blunted the HCVR at doses within the range typically used experimentally. At lower doses ventilation was decreased, but mice appropriately matched their ventilation to metabolic demands due to a parallel decrease in O2 consumption. Neither ketamine nor urethane decreased chemosensitivity of 5-HT neurons. These results indicate that baseline breathing and/or CO2 chemoreception in mice are decreased by anesthetics widely viewed as not affecting respiratory control, and even at subtherapeutic doses. These effects of anesthetics on breathing may alter the interpretation of studies of respiratory physiology in vivo.NEW & NOTEWORTHY Anesthetics are frequently used in animal research, but their effects on physiological functions in mice have not been well defined. Here we investigated the effects of commonly used anesthetics on breathing in mice. We found that all tested anesthetics significantly reduced the hypercapnic ventilatory response (HCVR), even at subtherapeutic doses. In addition, ketamine-xylazine and urethane anesthesia altered baseline breathing. These data indicate that breathing and the HCVR in mice are highly sensitive to anesthetic modulation.
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Affiliation(s)
- Cory A Massey
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa.,Department of Neurology, University of Iowa, Iowa City, Iowa
| | - George B Richerson
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa; .,Department of Neurology, University of Iowa, Iowa City, Iowa.,Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa; and.,Veterans Affairs Medical Center, Iowa City, Iowa
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19
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Taxini CL, Moreira TS, Takakura AC, Bícego KC, Gargaglioni LH, Zoccal DB. Role of A5 noradrenergic neurons in the chemoreflex control of respiratory and sympathetic activities in unanesthetized conditions. Neuroscience 2017; 354:146-157. [PMID: 28461215 DOI: 10.1016/j.neuroscience.2017.04.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/21/2017] [Accepted: 04/21/2017] [Indexed: 01/04/2023]
Abstract
The A5 area at the ventrolateral pons contains noradrenergic neurons connected with other medullary areas involved in the cardiorespiratory control. Its contribution to the cardiorespiratory regulation was previously evidenced in anesthetized conditions. In the present study, we investigated the involvement of the A5 noradrenergic neurons to the basal and chemoreflex control of the sympathetic and respiratory activities in unanesthetized conditions. A5 noradrenergic neurons were lesioned using microinjections of anti-dopamine β-hydroxylase saporin (anti-DβH-SAP). After 7-8days, we evaluated the arterial pressure levels, heart rate and minute ventilation in freely moving adult rats (280-350g) as well as recorded from thoracic sympathetic (tSN) and phrenic nerves (PN) using the arterially perfused in situ preparation of juvenile rats (80-90g). Baseline cardiovascular, sympathetic and respiratory parameters were similar between control (n=7-8) and A5-lesioned rats (n=5-6) in both experimental preparations. In adult rats, lesions of A5 noradrenergic neurons did not modify the reflex cardiorespiratory adjustments to hypoxia (7% O2) and hypercapnia (7% CO2). In the in situ preparations, the sympatho-excitation, but not the PN reflex response, elicited by either the stimulation of peripheral chemoreceptors (ΔtSN: 110±12% vs 58±8%, P<0.01) or hypercapnia (ΔtSN: 9.5±1.4% vs 3.9±1.7%, P<0.05) was attenuated in A5-lesioned rats compared to controls. Our data demonstrated that A5 noradrenergic neurons are part of the circuitry recruited for the processing of sympathetic response to hypoxia and hypercapnia in unanesthetized conditions.
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Affiliation(s)
- Camila L Taxini
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP, Brazil
| | - Kênia C Bícego
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil
| | - Luciane H Gargaglioni
- Department of Morphology and Animal Physiology, São Paulo State University (UNESP), Jaboticabal, SP, Brazil.
| | - Daniel B Zoccal
- Department of Physiology and Pathology, School of Dentistry, São Paulo State University (UNESP), Araraquara, SP, Brazil.
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20
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Cahill LS, Bishop J, Gazdzinski LM, Dorr A, Stefanovic B, Sled JG. Altered cerebral blood flow and cerebrovascular function after voluntary exercise in adult mice. Brain Struct Funct 2017; 222:3395-3405. [PMID: 28391400 DOI: 10.1007/s00429-017-1409-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 03/20/2017] [Indexed: 01/06/2023]
Abstract
The beneficial effects of physical exercise on brain health are well documented, yet how exercise modulates cerebrovascular function is not well understood. This study used continuous arterial spin labeling magnetic resonance imaging with a hypercapnic challenge to examine changes in cerebral blood flow and vascular function after voluntary exercise in healthy, adult mice. Thirty exercise mice and twenty-one control mice were imaged prior to the start of the exercise regime (at 12 weeks of age) and after 4 weeks of voluntary exercise. After the second in vivo imaging session, we performed high-resolution ex vivo anatomical brain imaging to correlate the structural brain changes with functional measures of flow and vascular reserve. We found that exercise resulted in increases in the normocapnic and hypercapnic blood flow in the hippocampus. Moreover, the change in normocapnic blood flow between pre-exercise and post-exercise was positively correlated to the hippocampal structure volume following exercise. There was no overall effect of voluntary exercise on blood flow in the motor cortex. Surprisingly, the hypercapnic hippocampal blood flow when measured prior to the start of exercise was predictive of subsequent exercise activity. Moreover, exercise was found to normalize this pre-existing difference in hypercapnic blood flow between mice.
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Affiliation(s)
- Lindsay S Cahill
- Mouse Imaging Centre, The Hospital for Sick Children, 25 Orde Street, Toronto, ON, M5T 2H7, Canada.
| | - Jonathan Bishop
- Mouse Imaging Centre, The Hospital for Sick Children, 25 Orde Street, Toronto, ON, M5T 2H7, Canada
| | - Lisa M Gazdzinski
- Mouse Imaging Centre, The Hospital for Sick Children, 25 Orde Street, Toronto, ON, M5T 2H7, Canada
| | | | - Bojana Stefanovic
- Sunnybrook Research Institute, Toronto, ON, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - John G Sled
- Mouse Imaging Centre, The Hospital for Sick Children, 25 Orde Street, Toronto, ON, M5T 2H7, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
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21
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Wren-Dail MA, Dauchy RT, Blask DE, Hill SM, Ooms TG, Dupepe LM, Bohm RP. Effect of Isoflurane Anesthesia on Circadian Metabolism and Physiology in Rats. Comp Med 2017; 67:138-146. [PMID: 28381314 PMCID: PMC5402733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 07/01/2016] [Accepted: 11/13/2016] [Indexed: 06/07/2023]
Abstract
Isoflurane anesthesia alters the blood levels of several neuroendocrine hormones associated with normal metabolism and physiology and increases stress, but the effect of brief CO2 anesthesia on these parameters is unknown. In this study, we examined the effects of isoflurane (4%) compared with brief CO2 (70% CO2, 30% air) anesthesia on circadian rhythms of plasma measures of physiology and metabolism. Adult male Sprague-Dawley rats (Crl:SD; n = 6 per group) were maintained on a 12:12-h light:dark (300 lx; lights on, 0600) photoperiod. After 1 wk of acclimation, a series of 6 low-volume blood draws were collected by cardiocentesis under anesthesia using isoflurane (10 min or less) compared with CO2 (1 min or less) at a single circadian time point every 4 d (0400, 0800, 1200, 1600, 2000, or 2400) over 3 wk to assess arterial blood glucose, lactic acid, and potassium and plasma melatonin, leptin, insulin, total fatty acids, and corticosterone concentrations. Results revealed that plasma levels (mean ± SEM) of melatonin were low (11 ± 1 pg/mL) during the light phase in both groups but were significantly lower during the dark phase in the isoflurane group (48 ± 6 pg/mL) compared with the CO2 group (162 ± 18 pg/mL). In addition, prominent circadian rhythms of arterial plasma levels of corticosterone, glucose, total fatty acids, lactic acid, and potassium were altered in the isoflurane group compared with the CO2 group. These findings demonstrate that the normal circadian rhythms of endocrine physiology and metabolism observed during brief CO2 anesthesia in rats are markedly disrupted by isoflurane anesthesia.
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Affiliation(s)
- Melissa A Wren-Dail
- Departments of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana;,
| | - Robert T Dauchy
- Departments of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - David E Blask
- Departments of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Steven M Hill
- Departments of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Tara G Ooms
- Section of Laboratory Animal Medicine, IIT Research Institute, Chicago, Illinois
| | - Lynell M Dupepe
- Departments of Comparative Medicine, Tulane University School of Medicine, New Orleans, Louisiana
| | - Rudolf P Bohm
- Division of Veterinary Medicine, Tulane National Primate Research Center, Covington, Louisiana
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22
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Activity of Tachykinin1-Expressing Pet1 Raphe Neurons Modulates the Respiratory Chemoreflex. J Neurosci 2017; 37:1807-1819. [PMID: 28073937 DOI: 10.1523/jneurosci.2316-16.2016] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/30/2016] [Accepted: 12/30/2016] [Indexed: 11/21/2022] Open
Abstract
Homeostatic control of breathing, heart rate, and body temperature relies on circuits within the brainstem modulated by the neurotransmitter serotonin (5-HT). Mounting evidence points to specialized neuronal subtypes within the serotonergic neuronal system, borne out in functional studies, for the modulation of distinct facets of homeostasis. Such functional differences, read out at the organismal level, are likely subserved by differences among 5-HT neuron subtypes at the cellular and molecular levels, including differences in the capacity to coexpress other neurotransmitters such as glutamate, GABA, thyrotropin releasing hormone, and substance P encoded by the Tachykinin-1 (Tac1) gene. Here, we characterize in mice a 5-HT neuron subtype identified by expression of Tac1 and the serotonergic transcription factor gene Pet1, referred to as the Tac1-Pet1 neuron subtype. Transgenic cell labeling showed Tac1-Pet1 soma resident largely in the caudal medulla. Chemogenetic [clozapine-N-oxide (CNO)-hM4Di] perturbation of Tac1-Pet1 neuron activity blunted the ventilatory response of the respiratory CO2 chemoreflex, which normally augments ventilation in response to hypercapnic acidosis to restore normal pH and PCO2Tac1-Pet1 axonal boutons were found localized to brainstem areas implicated in respiratory modulation, with highest density in motor regions. These findings demonstrate that the activity of a Pet1 neuron subtype with the potential to release both 5-HT and substance P is necessary for normal respiratory dynamics, perhaps via motor outputs that engage muscles of respiration and maintain airway patency. These Tac1-Pet1 neurons may act downstream of Egr2-Pet1 serotonergic neurons, which were previously established in respiratory chemoreception, but do not innervate respiratory motor nuclei.SIGNIFICANCE STATEMENT Serotonin (5-HT) neurons modulate physiological processes and behaviors as diverse as body temperature, respiration, aggression, and mood. Using genetic tools, we characterize a 5-HT neuron subtype defined by expression of Tachykinin1 and Pet1 (Tac1-Pet1 neurons), mapping soma localization to the caudal medulla primarily and axonal projections to brainstem motor nuclei most prominently, and, when silenced, observed blunting of the ventilatory response to inhaled CO2Tac1-Pet1 neurons thus appear distinct from and contrast previously described Egr2-Pet1 neurons, which project primarily to chemosensory integration centers and are themselves chemosensitive.
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Nonomura K, Woo SH, Chang RB, Gillich A, Qiu Z, Francisco AG, Ranade SS, Liberles SD, Patapoutian A. Piezo2 senses airway stretch and mediates lung inflation-induced apnoea. Nature 2016; 541:176-181. [PMID: 28002412 DOI: 10.1038/nature20793] [Citation(s) in RCA: 278] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 11/16/2016] [Indexed: 12/11/2022]
Abstract
Respiratory dysfunction is a notorious cause of perinatal mortality in infants and sleep apnoea in adults, but the mechanisms of respiratory control are not clearly understood. Mechanical signals transduced by airway-innervating sensory neurons control respiration; however, the physiological significance and molecular mechanisms of these signals remain obscured. Here we show that global and sensory neuron-specific ablation of the mechanically activated ion channel Piezo2 causes respiratory distress and death in newborn mice. Optogenetic activation of Piezo2+ vagal sensory neurons causes apnoea in adult mice. Moreover, induced ablation of Piezo2 in sensory neurons of adult mice causes decreased neuronal responses to lung inflation, an impaired Hering-Breuer mechanoreflex, and increased tidal volume under normal conditions. These phenotypes are reproduced in mice lacking Piezo2 in the nodose ganglion. Our data suggest that Piezo2 is an airway stretch sensor and that Piezo2-mediated mechanotransduction within various airway-innervating sensory neurons is critical for establishing efficient respiration at birth and maintaining normal breathing in adults.
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Affiliation(s)
- Keiko Nonomura
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Seung-Hyun Woo
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Rui B Chang
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Astrid Gillich
- Howard Hughes Medical Institute, Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Zhaozhu Qiu
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA.,Genomics Institute of the Novartis Research Foundation, San Diego, California 92121, USA
| | - Allain G Francisco
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Sanjeev S Ranade
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Stephen D Liberles
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Ardem Patapoutian
- Howard Hughes Medical Institute, Molecular and Cellular Neuroscience, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, California 92037, USA
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Ramirez S, Allen T, Villagracia L, Chae Y, Ramirez JM, Rubens DD. Inner ear lesion and the differential roles of hypoxia and hypercarbia in triggering active movements: Potential implication for the Sudden Infant Death Syndrome. Neuroscience 2016; 337:9-16. [PMID: 27634772 DOI: 10.1016/j.neuroscience.2016.08.054] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 08/29/2016] [Accepted: 08/31/2016] [Indexed: 01/12/2023]
Abstract
Infants that succumb to Sudden Infant Death Syndrome (SIDS) have been identified with inner ear dysfunction (IED) at birth and on autopsy. We previously investigated whether IED could play a mechanistic role in SIDS. We discovered that animals with IED displayed significant suppression of movement arousal to a hypoxic-hypercarbic gas mixture under light anesthesia. In the current study we investigated the role of each gas in triggering movements and the response to hypercarbia during natural sleep without anesthesia. Seventeen-day-old CD-1 mice received intra-tympanic gentamicin (IT-Gent) injections to precipitate IED. The movement response to hypercarbia, hypoxia and hypoxia-hypercarbia was compared to controls under light anesthesia. Hypercarbia did not stimulate vigorous movements in any animals under either sleep condition. Hypoxia triggered vigorous movements in controls (p<0.05) and a decreased response in IT-Gent animals under light anesthesia. This contrasted with combined hypoxia-hypercarbia, in which IT-Gent animals displaced significantly suppressed movements compared to controls (p<0.05). Our findings portray that a degree of intact inner ear function is necessary for instigating the movement response. Additionally, hypoxia is the trigger for the movement response while carbon dioxide (CO2) suppresses it. The finding that carbon dioxide did not stimulate movement during natural sleep is an important finding. This contrasts with other studies that have identified hypercarbia as an arousal stimulus with EEG. Further studies are warranted to evaluate the precise role of the inner ear in the movement response and potential association with SIDS. The early detection of IED in SIDS predisposed cases could be invaluable.
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Affiliation(s)
- Sanja Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States
| | - Travis Allen
- Department of Anesthesia, Seattle Children's Hospital, 4800 Sandpoint Way NE, Seattle, WA 98105, United States; Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States; Department of Anesthesia, University of Washington, Seattle, WA, United States
| | - Lindsay Villagracia
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States
| | - Yooree Chae
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States
| | - Jan M Ramirez
- Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States; Department of Pediatrics, University of Washington, Seattle, WA, United States
| | - Daniel D Rubens
- Department of Anesthesia, Seattle Children's Hospital, 4800 Sandpoint Way NE, Seattle, WA 98105, United States; Center for Integrative Brain Research, Seattle Children's Research Institute, 1900 Ninth Avenue, Seattle, WA 98101, United States; Department of Anesthesia, University of Washington, Seattle, WA, United States.
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Tachikawa S, Nakayama K, Nakamura S, Mochizuki A, Iijima T, Inoue T. Coordinated Respiratory Motor Activity in Nerves Innervating the Upper Airway Muscles in Rats. PLoS One 2016; 11:e0166436. [PMID: 27832132 PMCID: PMC5104329 DOI: 10.1371/journal.pone.0166436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 10/28/2016] [Indexed: 12/02/2022] Open
Abstract
Maintaining the patency of the upper airway during breathing is of vital importance. The activity of various muscles is related to the patency of the upper airway. In the present study, we examined the respiratory motor activity in the efferent nerves innervating the upper airway muscles to determine the movements of the upper airway during respiration under normocapnic conditions (pH = 7.4) and in hypercapnic acidosis (pH = 7.2). Experiments were performed on arterially perfused decerebrate rats aged between postnatal days 21–35. We recorded the efferent nerve activity in a branch of the cervical spinal nerve innervating the infrahyoid muscles (CN), the hypoglossal nerve (HGN), the external branch of the superior laryngeal nerve (SLN), and the recurrent laryngeal nerve (RLN) with the phrenic nerve (PN). Inspiratory nerve discharges were observed in all these nerves under normocapnic conditions. The onset of inspiratory discharges in the CN and HGN was slightly prior to those in the SLN and RLN. When the CO2 concentration in the perfusate was increased from 5% to 8% to prepare for hypercapnic acidosis, the peak amplitudes of the inspiratory discharges in all the recorded nerves were increased. Moreover, hypercapnic acidosis induced pre-inspiratory discharges in the CN, HGN, SLN, and RLN. The onset of pre-inspiratory discharges in the CN, HGN, and SLN was prior to that of discharges in the RLN. These results suggest that the securing of the airway that occurs a certain time before dilation of the glottis may facilitate ventilation and improve hypercapnic acidosis.
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Affiliation(s)
- Satoshi Tachikawa
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Kiyomi Nakayama
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
- * E-mail:
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Ayako Mochizuki
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
| | - Takehiko Iijima
- Department of Perioperative Medicine, Division of Anesthesiology, Showa University School of Dentistry, Oota-ku, Tokyo 145–8515, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, Shinagawa-ku, Tokyo 142–8555, Japan
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Totola LT, Takakura AC, Oliveira JAC, Garcia-Cairasco N, Moreira TS. Impaired central respiratory chemoreflex in an experimental genetic model of epilepsy. J Physiol 2016; 595:983-999. [PMID: 27633663 DOI: 10.1113/jp272822] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 09/12/2016] [Indexed: 12/22/2022] Open
Abstract
KEY POINTS It is recognized that seizures commonly cause apnoea and oxygen desaturation, but there is still a lack in the literature about the respiratory impairments observed ictally and in the post-ictal period. Respiratory disorders may involve changes in serotonergic transmission at the level of the retrotrapezoid nucleus (RTN). In this study, we evaluated breathing activity and the role of serotonergic transmission in the RTN with a rat model of tonic-clonic seizures, the Wistar audiogenic rat (WAR). We conclude that the respiratory impairment in the WAR could be correlated to an overall decrease in the number of neurons located in the respiratory column. ABSTRACT Respiratory disorders may involve changes in serotonergic neurotransmission at the level of the chemosensitive neurons located in the retrotrapezoid nucleus (RTN). Here, we investigated the central respiratory chemoreflex and the role of serotonergic neurotransmission in the RTN with a rat model of tonic-clonic seizures, the Wistar audiogenic rat (WAR). We found that naive or kindled WARs have reduced resting ventilation and ventilatory response to hypercapnia (7% CO2 ). The number of chemically coded (Phox2b+ /TH- ) RTN neurons, as well as the serotonergic innervation to the RTN, was reduced in WARs. We detected that the ventilatory response to serotonin (1 mm, 50 nl) within the RTN region was significantly reduced in WARs. Our results uniquely demonstrated a respiratory impairment in a genetic model of tonic-clonic seizures, the WAR strain. More importantly, we demonstrated an overall decrease in the number of neurons located in the ventral respiratory column (VRC), as well as a reduction in serotonergic neurons in the midline medulla. This is an important step forward to demonstrate marked changes in neuronal activity and breathing impairment in the WAR strain, a genetic model of epilepsy.
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Affiliation(s)
- Leonardo T Totola
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 05508-000, São Paulo, SP, Brazil
| | - Ana C Takakura
- Department of Pharmacology, Institute of Biomedical Science, University of São Paulo, 05508-000, São Paulo, SP, Brazil
| | - José Antonio C Oliveira
- Department of Physiology, Ribeirão Preto School of Medicine, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil
| | - Norberto Garcia-Cairasco
- Department of Physiology, Ribeirão Preto School of Medicine, University of São Paulo, 14049-900, Ribeirão Preto, SP, Brazil
| | - Thiago S Moreira
- Department of Physiology and Biophysics, Institute of Biomedical Science, University of São Paulo, 05508-000, São Paulo, SP, Brazil
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Bhandare AM, Kapoor K, Farnham MM, Pilowsky PM. Microglia PACAP and glutamate: Friends or foes in seizure-induced autonomic dysfunction and SUDEP? Respir Physiol Neurobiol 2016; 226:39-50. [DOI: 10.1016/j.resp.2016.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 01/18/2016] [Accepted: 01/21/2016] [Indexed: 12/18/2022]
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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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Spray S, Edvinsson L. Improved assessment of outcomes following transient global cerebral ischemia in mice. Exp Brain Res 2016; 234:1925-1934. [DOI: 10.1007/s00221-016-4597-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/11/2016] [Indexed: 11/28/2022]
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Johansen SL, Iceman KE, Iceman CR, Taylor BE, Harris MB. Isoflurane causes concentration-dependent inhibition of medullary raphé 5-HT neurons in situ. Auton Neurosci 2015. [PMID: 26213357 DOI: 10.1016/j.autneu.2015.07.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Anesthetics have a profound influence on a myriad of autonomic processes. Mechanisms of general anesthesia, and how these mechanisms give rise to the multifaceted state of anesthesia, are largely unknown. The ascending and descending serotonin (5-HT) networks are key modulators of autonomic pathways, and are critically involved in homeostatic reflexes across the motor, somatosensory, limbic and autonomic systems. These 5-HT networks are thought to contribute to anesthetic effects, but how anesthetics affect 5-HT neuron function remains a pertinent question. We hypothesized that the volatile anesthetic isoflurane inhibits action potential discharge of medullary raphé 5-HT neurons. METHODS We conducted extracellular recordings on individual neurons in the medullary raphé region of the unanesthetized in situ perfused brainstem preparation to determine how exposure to isoflurane affects 5-HT neurons. We examined changes in 5-HT neuron baseline firing in response to treatment with either 1, 1.5, or 2% isoflurane. We measured isoflurane concentrations by gas chromatography-mass spectrometry (GC-MS) analysis. RESULTS Exposure to isoflurane inhibited action potential discharge in raphé 5-HT neurons. We document a concentration-dependent inhibition over a range of concentrations approximating isoflurane MAC (minimum alveolar concentration required for surgical anesthesia). Delivered concentrations of isoflurane were confirmed using GC-MS analysis. CONCLUSIONS These findings illustrate that halogenated anesthetics greatly affect 5-HT neuron firing and suggest 5-HT neuron contributions to mechanisms of general anesthesia.
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Affiliation(s)
- S L Johansen
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - K E Iceman
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - C R Iceman
- Department of Chemistry and Biochemistry, University of Alaska, Fairbanks, AK 99775, USA
| | - B E Taylor
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA
| | - M B Harris
- Institute of Arctic Biology, Department of Biology and Wildlife, University of Alaska, Fairbanks, AK 99775, USA.
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Corcoran AE, Richerson GB, Harris MB. Functional link between the hypocretin and serotonin systems in the neural control of breathing and central chemosensitivity. J Neurophysiol 2015; 114:381-9. [PMID: 25878157 DOI: 10.1152/jn.00870.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 04/09/2015] [Indexed: 11/22/2022] Open
Abstract
Serotonin (5-HT)-synthesizing neurons of the medullary raphe are putative central chemoreceptors, proposed to be one of potentially multiple brain stem chemosensitive cell types and loci interacting to produce the respiratory chemoreflex. Hypocretin-synthesizing neurons of the lateral hypothalamus are important contributors to arousal state, thermoregulation, and feeding behavior and are also reportedly involved in the hypercapnic ventilatory response. Recently, a functional interaction was found between the hypocretin system and 5-HT neurons of the dorsal raphe. The validity and potential significance of hypocretin modulation of medullary raphe 5-HT neurons, however, is unknown. As such, the purpose of this study was to explore functional interactions between the hypocretin system and 5-HT system of the medullary raphe on baseline respiratory output and central chemosensitivity. To explore such interactions, we used the neonatal in vitro medullary slice preparation derived from wild-type (WT) mice (normal 5-HT function) and a knockout strain lacking all central 5-HT neurons (Lmx1b(f/f/p) mice). We examined effects of acidosis, hypocretin-1, a hypocretin receptor antagonist (SB-408124), and the effect of the antagonist on the response to acidosis. We confirmed the critical role of 5-HT neurons in central chemosensitivity given that the increased hypoglossal burst frequency with acidosis, characteristic of WT mice, was absent in preparations derived from Lmx1b(f/f/p) mice. We also found that hypocretin facilitated baseline neural ventilatory output in part through 5-HT neurons. Although the impact of hypocretin on 5-HT neuronal sensitivity to acidosis is still unclear, hypocretins did appear to mediate the burst duration response to acidosis via serotonergic mechanisms.
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Affiliation(s)
- Andrea E Corcoran
- Department of Biology and Wildlife, and Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska; Departments of Neurology and Cellular & Molecular Physiology, Yale University, New Haven, Connecticut; Department of Physiology and Neurobiology, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire;
| | - George B Richerson
- Departments of Neurology and Cellular & Molecular Physiology, Yale University, New Haven, Connecticut; Veteran's Affairs Medical Center, West Haven, Connecticut; and Departments of Neurology and Molecular Physiology & Biophysics, University of Iowa, Iowa City, Iowa
| | - Michael B Harris
- Department of Biology and Wildlife, and Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska
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