1
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Hutchens SED, Khurram I, Hurley LM. Solitude and serotonin: juvenile isolation alters the covariation between social behavior and cFos expression by serotonergic neurons. Front Neurosci 2024; 18:1446866. [PMID: 39502712 PMCID: PMC11535725 DOI: 10.3389/fnins.2024.1446866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2024] [Accepted: 09/19/2024] [Indexed: 11/08/2024] Open
Abstract
Variation in the mutual responsiveness of social partners to each other can be reflected in behavioral suites that covary with neural activity in ways that track the salience or valence of interactions. Juvenile social isolation alters social behavior and neural activity during social interaction, but whether and how it alters the covariation between behavior and neural activity has not been as well explored. To address this issue, four classes of experimental subjects: isolated males, socially housed males, isolated females, and socially housed females, were paired with an opposite-sex social partner that had been socially housed. Social behaviors and c-Fos expression in the serotonergic dorsal raphe nucleus (DRN) were then measured in subjects following the social interactions. Relative to social housing, postweaning isolation led to a decrease in the density of neurons double-labeled for tryptophan hydroxylase and c-Fos in the dorsomedial subdivision of the DRN, regardless of sex. Vocal and non-vocal behaviors were also affected by isolation. In interactions with isolated males, both ultrasonic vocalization (USVs) and broadband vocalizations (squeaks) increased in conjunction with greater male investigation of females. Neural and behavioral measures also correlated with each other. In the isolated male group, the density of double-labeled neurons in the dorsomedial DRN was negatively correlated with USV production and positively correlated with a principal component of non-vocal behavior corresponding to greater defensive kicking by females and less investigation and mounting behavior. This correlation was reversed in direction for socially housed males, and for isolated males versus isolated females. These findings confirm that the dynamics of social interactions are reflected in c-Fos activation in the dorsomedial DRN, and suggest an altered responsiveness of serotonergic neurons to social interaction following social isolation in males, in parallel with an altered male response to female cues.
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Affiliation(s)
- Sarah E. D. Hutchens
- Hurley Laboratory, Department of Biology, Indiana University, Bloomington, IN, United States
| | - Izza Khurram
- Hurley Laboratory, Department of Biology, Indiana University, Bloomington, IN, United States
| | - Laura M. Hurley
- Hurley Laboratory, Department of Biology, Indiana University, Bloomington, IN, United States
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
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2
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Jellinger KA. Behavioral disorders in dementia with Lewy bodies: old and new knowledge. J Neural Transm (Vienna) 2024:10.1007/s00702-024-02823-w. [PMID: 39237792 DOI: 10.1007/s00702-024-02823-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Accepted: 08/07/2024] [Indexed: 09/07/2024]
Abstract
Dementia with Lewy bodies (DLB), the second most common primary degenerative neurocognitive disorder after Alzheimer disease, is frequently preceded by REM sleep behavior disorders (RBD) and other behavioral symptoms, like anxiety, irritability, agitation or apathy, as well as visual hallucinations and delusions, most of which occurring in 40-60% of DLB patients. Other frequent behavioral symptoms like attention deficits contribute to cognitive impairment, while attention-deficit/hyperactivity disorder (ADHD) is a risk factor for DLB. Behavioral problems in DLB are more frequent, more severe and appear earlier than in other neurodegenerative diseases and, together with other neuropsychiatric symptoms, contribute to impairment of quality of life of the patients, but their pathophysiology is poorly understood. Neuroimaging studies displayed deficits in cholinergic brainstem nuclei and decreased metabolism in frontal, superior parietal regions, cingulate gyrus and amygdala in DLB. Early RBD in autopsy-confirmed DLB is associated with lower Braak neuritic stages, whereas those without RBD has greater atrophy of hippocampus and increased tau burden. αSyn pathology in the amygdala, a central region in the fear circuitry, may contribute to the high prevalence of anxiety, while in attention dysfunctions the default mode and dorsal attention networks displayed diverging activity. These changes suggest that behavioral disorders in DLB are associated with marked impairment in large-scale brain structures and functional connectivity network disruptions. However, many pathobiological mechanisms involved in the development of behavioral disorders in DLB await further elucidation in order to allow an early diagnosis and adequate treatment to prevent progression of these debilitating disorders.
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Affiliation(s)
- Kurt A Jellinger
- Institute of Clinical Neurobiology, Alberichgasse 5/13, Vienna, A-1150, Austria.
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3
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Chen HC, He P, McDonald M, Williamson MR, Varadharajan S, Lozzi B, Woo J, Choi DJ, Sardar D, Huang-Hobbs E, Sun H, Ippagunta SM, Jain A, Rao G, Merchant TE, Ellison DW, Noebels JL, Bertrand KC, Mack SC, Deneen B. Histone serotonylation regulates ependymoma tumorigenesis. Nature 2024; 632:903-910. [PMID: 39085609 DOI: 10.1038/s41586-024-07751-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 06/25/2024] [Indexed: 08/02/2024]
Abstract
Bidirectional communication between tumours and neurons has emerged as a key facet of the tumour microenvironment that drives malignancy1,2. Another hallmark feature of cancer is epigenomic dysregulation, in which alterations in gene expression influence cell states and interactions with the tumour microenvironment3. Ependymoma (EPN) is a paediatric brain tumour that relies on epigenomic remodelling to engender malignancy4,5; however, how these epigenetic mechanisms intersect with extrinsic neuronal signalling during EPN tumour progression is unknown. Here we show that the activity of serotonergic neurons regulates EPN tumorigenesis, and that serotonin itself also serves as an activating modification on histones. We found that inhibiting histone serotonylation blocks EPN tumorigenesis and regulates the expression of a core set of developmental transcription factors. High-throughput, in vivo screening of these transcription factors revealed that ETV5 promotes EPN tumorigenesis and functions by enhancing repressive chromatin states. Neuropeptide Y (NPY) is one of the genes repressed by ETV5, and its overexpression suppresses EPN tumour progression and tumour-associated network hyperactivity through synaptic remodelling. Collectively, this study identifies histone serotonylation as a key driver of EPN tumorigenesis, and also reveals how neuronal signalling, neuro-epigenomics and developmental programs are intertwined to drive malignancy in brain cancer.
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Affiliation(s)
- Hsiao-Chi Chen
- Program in Cancer and Cell Biology, Baylor College of Medicine, Houston, TX, USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX, USA
| | - Peihao He
- Program in Cancer and Cell Biology, Baylor College of Medicine, Houston, TX, USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Malcolm McDonald
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Program in Development, Disease, Models and Therapeutics, Baylor College of Medicine, Houston, TX, USA
| | - Michael R Williamson
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Srinidhi Varadharajan
- Center of Excellence in Neuro-Oncology Sciences (CENOS), St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Brittney Lozzi
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Program in Genetics and Genomics, Baylor College of Medicine, Houston, TX, USA
| | - Junsung Woo
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Dong-Joo Choi
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Debosmita Sardar
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Emmet Huang-Hobbs
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX, USA
| | - Hua Sun
- Center of Excellence in Neuro-Oncology Sciences (CENOS), St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Siri M Ippagunta
- Center of Excellence in Neuro-Oncology Sciences (CENOS), St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Antrix Jain
- Mass Spectrometry Proteomics Core, Baylor College of Medicine, Houston, TX, USA
| | - Ganesh Rao
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA
| | - Thomas E Merchant
- Department of Radiation Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - David W Ellison
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Jeffrey L Noebels
- Department of Human and Molecular Genetics, Baylor College of Medicine, Houston, TX, USA
- Department of Neurology, Baylor College of Medicine, Houston, TX, USA
| | - Kelsey C Bertrand
- Division of Neuro-Oncology, Department of Oncology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Stephen C Mack
- Center of Excellence in Neuro-Oncology Sciences (CENOS), St. Jude Children's Research Hospital, Memphis, TN, USA.
- Department of Developmental Neurobiology, St Jude Children's Research Hospital, Memphis, TN, USA.
- Neurobiology and Brain Tumor Program, St Jude Children's Research Hospital, Memphis, TN, USA.
| | - Benjamin Deneen
- Program in Cancer and Cell Biology, Baylor College of Medicine, Houston, TX, USA.
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, TX, USA.
- Center for Cancer Neuroscience, Baylor College of Medicine, Houston, TX, USA.
- Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX, USA.
- Program in Development, Disease, Models and Therapeutics, Baylor College of Medicine, Houston, TX, USA.
- Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.
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4
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Chen M, Wang C, Lin Y, Chen Y, Xie W, Huang X, Zhang F, Fu C, Zhuang K, Zou T, Can D, Li H, Wu S, Luo C, Zhang J. Dorsal raphe nucleus-hippocampus serotonergic circuit underlies the depressive and cognitive impairments in 5×FAD male mice. Transl Neurodegener 2024; 13:34. [PMID: 39044270 PMCID: PMC11267773 DOI: 10.1186/s40035-024-00425-w] [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: 12/04/2023] [Accepted: 06/19/2024] [Indexed: 07/25/2024] Open
Abstract
BACKGROUND Depressive symptoms often occur in patients with Alzheimer's disease (AD) and exacerbate the pathogenesis of AD. However, the neural circuit mechanisms underlying the AD-associated depression remain unclear. The serotonergic system plays crucial roles in both AD and depression. METHODS We used a combination of in vivo trans-synaptic circuit-dissecting anatomical approaches, chemogenetic manipulations, optogenetic manipulations, pharmacological methods, behavioral testing, and electrophysiological recording to investigate dorsal raphe nucleus serotonergic circuit in AD-associated depression in AD mouse model. RESULTS We found that the activity of dorsal raphe nucleus serotonin neurons (DRN5-HT) and their projections to the dorsal hippocampal CA1 (dCA1) terminals (DRN5-HT-dCA1CaMKII) both decreased in brains of early 5×FAD mice. Chemogenetic or optogenetic activation of the DRN5-HT-dCA1CaMKII neural circuit attenuated the depressive symptoms and cognitive impairments in 5×FAD mice through serotonin receptor 1B (5-HT1BR) and 4 (5-HT4R). Pharmacological activation of 5-HT1BR or 5-HT4R attenuated the depressive symptoms and cognitive impairments in 5×FAD mice by regulating the DRN5-HT-dCA1CaMKII neural circuit to improve synaptic plasticity. CONCLUSIONS These findings provide a new mechanistic connection between depression and AD and provide potential pharmaceutical prevention targets for AD.
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Affiliation(s)
- Meiqin Chen
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, College of Basic Medicine, Hebei Medical University, Shijiazhuang, 050017, China
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Chenlu Wang
- Department of Anesthesiology, First Affiliated Hospital of Xiamen University, Xiamen, 361000, China
| | - Yinan Lin
- Department of Anesthesiology, First Affiliated Hospital of Xiamen University, Xiamen, 361000, China
| | - Yanbing Chen
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Wenting Xie
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Xiaoting Huang
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Fan Zhang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, College of Basic Medicine, Hebei Medical University, Shijiazhuang, 050017, China
| | - Congrui Fu
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, College of Basic Medicine, Hebei Medical University, Shijiazhuang, 050017, China
| | - Kai Zhuang
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Tingting Zou
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Dan Can
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Huifang Li
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China
| | - Shengxi Wu
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Ceng Luo
- Department of Neurobiology, School of Basic Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Jie Zhang
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, College of Basic Medicine, Hebei Medical University, Shijiazhuang, 050017, China.
- Institute of Neuroscience, College of Medicine, Xiamen University, Xiamen, 361102, China.
- Department of Neurology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, 610054, China.
- Institute of Neuroscience, Fujian Medical University, Fuzhou, 350004, China.
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5
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Tan H, Du C, Zhang L, Guo Y, Yang Y, Sun Q, Zhang Q, Li L. Lesions of the lateral habenula excite dopamine neurons in the ventral tegmental area and serotonin neurons in the dorsal raphe nuclei in hemiparkinsonian rats. Brain Res 2024; 1835:148918. [PMID: 38588847 DOI: 10.1016/j.brainres.2024.148918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 03/20/2024] [Accepted: 04/05/2024] [Indexed: 04/10/2024]
Abstract
The lateral habenula (LHb) projects to the ventral tegmental area (VTA) and dorsal raphe nuclei (DRN) that deliver dopamine (DA) and serotonin (5-HT) to cortical and limbic regions such as the medial prefrontal cortex (mPFC), hippocampus and basolateral amygdala (BLA). Dysfunctions of VTA-related mesocorticolimbic dopaminergic and DRN-related serotonergic systems contribute to non-motor symptoms in Parkinson's disease (PD). However, how the LHb affects the VTA and DRN in PD remains unclear. Here, we used electrophysiological and neurochemical approaches to explore the effects of LHb lesions on the firing activity of VTA and DRN neurons, as well as the levels of DA and 5-HT in related brain regions in unilateral 6-hydroxydopamie (6-OHDA)-induced PD rats. We found that compared to sham lesions, lesions of the LHb increased the firing rate of DA neurons in the VTA and 5-HT neurons in the DRN, but decreased the firing rate of GABAergic neurons in the same nucleus. In addition, lesions of the LHb increased the levels of DA and 5-HT in the mPFC, ventral hippocampus and BLA compared to sham lesions. These findings suggest that lesions of the LHb enhance the activity of mesocorticolimbic dopaminergic and serotonergic systems in PD.
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Affiliation(s)
- Huihui Tan
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China
| | - Chengxue Du
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China
| | - Li Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, China
| | - Yuan Guo
- Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, China
| | - Yaxin Yang
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China
| | - Qingfeng Sun
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China
| | - Qiaojun Zhang
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China.
| | - Libo Li
- Department of Rehabilitation Medicine, The Second Affiliated Hospital, Xi'an Jiaotong University, Xi'an 710004, China.
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6
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Corradetti D, Bernardi A, Corradetti R. Deep learning models for atypical serotonergic cells recognition. J Neurosci Methods 2024; 407:110158. [PMID: 38703797 DOI: 10.1016/j.jneumeth.2024.110158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 04/15/2024] [Accepted: 04/28/2024] [Indexed: 05/06/2024]
Abstract
BACKGROUND The serotonergic system modulates brain processes via functionally distinct subpopulations of neurons with heterogeneous properties, including their electrophysiological activity. In extracellular recordings, serotonergic neurons to be investigated for their functional properties are commonly identified on the basis of "typical" features of their activity, i.e. slow regular firing and relatively long duration of action potentials. Thus, due to the lack of equally robust criteria for discriminating serotonergic neurons with "atypical" features from non-serotonergic cells, the physiological relevance of the diversity of serotonergic neuron activities results largely understudied. NEW METHODS We propose deep learning models capable of discriminating typical and atypical serotonergic neurons from non-serotonergic cells with high accuracy. The research utilized electrophysiological in vitro recordings from serotonergic neurons identified by the expression of fluorescent proteins specific to the serotonergic system and non-serotonergic cells. These recordings formed the basis of the training, validation, and testing data for the deep learning models. The study employed convolutional neural networks (CNNs), known for their efficiency in pattern recognition, to classify neurons based on the specific characteristics of their action potentials. RESULTS The models were trained on a dataset comprising 27,108 original action potential samples, alongside an extensive set of 12 million synthetic action potential samples, designed to mitigate the risk of overfitting the background noise in the recordings, a potential source of bias. Results show that the models achieved high accuracy and were further validated on "non-homogeneous" data, i.e., data unknown to the model and collected on different days from those used for the training of the model, to confirm their robustness and reliability in real-world experimental conditions. COMPARISON WITH EXISTING METHODS Conventional methods for identifying serotonergic neurons allow recognition of serotonergic neurons defined as typical. Our model based on the analysis of the sole action potential reliably recognizes over 94% of serotonergic neurons including those with atypical features of spike and activity. CONCLUSION The model is ready for use in experiments conducted with the here described recording parameters. We release the codes and procedures allowing to adapt the model to different acquisition parameters or for identification of other classes of spontaneously active neurons.
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Affiliation(s)
- Daniele Corradetti
- Grupo de Fisica Matematica, Instituto Superior Tecnico, Av. Rovisco Pais, Lisboa, 1049-001, Portugal; Departamento de Matematica, Universidade do Algarve, Campus de Gambelas, Faro, 8005-139, Faro, Portugal.
| | | | - Renato Corradetti
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Viale G. Pieraccini 6, Firenze, 50139, Toscana, Italy.
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7
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Hood KE, Hurley LM. Listening to your partner: serotonin increases male responsiveness to female vocal signals in mice. Front Hum Neurosci 2024; 17:1304653. [PMID: 38328678 PMCID: PMC10847236 DOI: 10.3389/fnhum.2023.1304653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/28/2023] [Indexed: 02/09/2024] Open
Abstract
The context surrounding vocal communication can have a strong influence on how vocal signals are perceived. The serotonergic system is well-positioned for modulating the perception of communication signals according to context, because serotonergic neurons are responsive to social context, influence social behavior, and innervate auditory regions. Animals like lab mice can be excellent models for exploring how serotonin affects the primary neural systems involved in vocal perception, including within central auditory regions like the inferior colliculus (IC). Within the IC, serotonergic activity reflects not only the presence of a conspecific, but also the valence of a given social interaction. To assess whether serotonin can influence the perception of vocal signals in male mice, we manipulated serotonin systemically with an injection of its precursor 5-HTP, and locally in the IC with an infusion of fenfluramine, a serotonin reuptake blocker. Mice then participated in a behavioral assay in which males suppress their ultrasonic vocalizations (USVs) in response to the playback of female broadband vocalizations (BBVs), used in defensive aggression by females when interacting with males. Both 5-HTP and fenfluramine increased the suppression of USVs during BBV playback relative to controls. 5-HTP additionally decreased the baseline production of a specific type of USV and male investigation, but neither drug treatment strongly affected male digging or grooming. These findings show that serotonin modifies behavioral responses to vocal signals in mice, in part by acting in auditory brain regions, and suggest that mouse vocal behavior can serve as a useful model for exploring the mechanisms of context in human communication.
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Affiliation(s)
- Kayleigh E. Hood
- Hurley Lab, Department of Biology, Indiana University, Bloomington, IN, United States
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
| | - Laura M. Hurley
- Hurley Lab, Department of Biology, Indiana University, Bloomington, IN, United States
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, United States
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8
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Jellinger KA. Depression in dementia with Lewy bodies: a critical update. J Neural Transm (Vienna) 2023; 130:1207-1218. [PMID: 37418037 DOI: 10.1007/s00702-023-02669-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 06/28/2023] [Indexed: 07/08/2023]
Abstract
Depression with an estimated prevalence of 35% is a frequent manifestation of dementia with Lewy bodies (DLB), having negative effects on cognitive performance and life expectancy, yet the underlying neurobiology is poorly understood and most likely heterogeneous. Depressive symptoms in DLB can occur during the clinical course and, together with apathy, is a common prodromal neuropsychiatric symptom of this neurocognitive disorder in the group of Lewy body synucleinopathies. There are no essential differences in the frequency of depression in DLB and Parkinson disease-dementia (PDD), while its severity is up to twice as high as in Alzheimer disease (AD). Depression in DLB that is frequently underdiagnosed and undertreated, has been related to a variety of pathogenic mechanisms associated with the basic neurodegenerative process, in particular dysfunctions of neurotransmitter systems (decreased monoaminergic/serotonergic, noradrenergic and dopaminergic metabolism), α-synuclein pathology, synaptic zinc dysregulation, proteasome inhibition, gray matter volume loss in prefrontal and temporal areas as well as dysfunction of neuronal circuits with decreased functional connectivity of specific brain networks. Pharmacotherapy should avoid tricyclic antidepressants (anticholinergic adverse effects), second-generation antidepressants being a better choice, while modified electroconvulsive therapy, transcranial magnetic stimulation therapy and deep brain stimulation may be effective for pharmacotherapy-resistant cases. Since compared to depression in other dementias like Alzheimer disease and other parkinsonian syndromes, our knowledge of its molecular basis is limited, and further studies to elucidate the heterogeneous pathogenesis of depression in DLB are warranted.
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Affiliation(s)
- Kurt A Jellinger
- Institute of Clinical Neurobiology, Alberichgasse 5/13, 1150, Vienna, Austria.
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9
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Chiu YT, Deutch AY, Wang W, Schmitz GP, Huang KL, Kocak DD, Llorach P, Bowyer K, Liu B, Sciaky N, Hua K, Chen C, Mott SE, Niehaus J, DiBerto JF, English J, Walsh JJ, Scherrer G, Herman MA, Wu Z, Wetsel WC, Roth BL. A suite of engineered mice for interrogating psychedelic drug actions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.25.559347. [PMID: 37808655 PMCID: PMC10557740 DOI: 10.1101/2023.09.25.559347] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Psychedelic drugs like lysergic acid diethylamide (LSD) and psilocybin have emerged as potentially transformative therapeutics for many neuropsychiatric diseases, including depression, anxiety, post-traumatic stress disorder, migraine, and cluster headaches. LSD and psilocybin exert their psychedelic effects via activation of the 5-hydroxytryptamine 2A receptor (HTR2A). Here we provide a suite of engineered mice useful for clarifying the role of HTR2A and HTR2A-expressing neurons in psychedelic drug actions. We first generated Htr2a-EGFP-CT-IRES-CreERT2 mice (CT:C-terminus) to independently identify both HTR2A-EGFP-CT receptors and HTR2A-containing cells thereby providing a detailed anatomical map of HTR2A and identifying cell types that express HTR2A. We also generated a humanized Htr2a mouse line and an additional constitutive Htr2A-Cre mouse line. Psychedelics induced a variety of known behavioral changes in our mice validating their utility for behavioral studies. Finally, electrophysiology studies revealed that extracellular 5-HT elicited a HTR2A-mediated robust increase in firing of genetically-identified pyramidal neurons--consistent with a plasma membrane localization and mode of action. These mouse lines represent invaluable tools for elucidating the molecular, cellular, pharmacological, physiological, behavioral, and other actions of psychedelic drugs in vivo.
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Affiliation(s)
- Yi-Ting Chiu
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Ariel Y. Deutch
- Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | - Wei Wang
- Appel Alzheimer’s Disease Research Institute, Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, 10021, USA
| | - Gavin P Schmitz
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Karen Lu Huang
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - D. Dewran Kocak
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Pierre Llorach
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kasey Bowyer
- Appel Alzheimer’s Disease Research Institute, Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, 10021, USA
| | - Bei Liu
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Noah Sciaky
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Kunjie Hua
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Chongguang Chen
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Sarah E. Mott
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Jesse Niehaus
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeffrey F. DiBerto
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Justin English
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
| | - Jessica J. Walsh
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Grégory Scherrer
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- UNC Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- New York Stem Cell Foundation ‒ Robertson Investigator, Chapel Hill, NC 27599, USA
| | - Melissa A Herman
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Zhuhao Wu
- Appel Alzheimer’s Disease Research Institute, Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, 10021, USA
| | - William C Wetsel
- Departments of Psychiatry and Behavioral Sciences, Cell Biology, and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
- Mouse Behavioral and Neuroendocrine Analysis Core Facility, Duke University Medical Center, Durham, NC 27710, USA
| | - Bryan L Roth
- Department of Pharmacology, University of North Carolina at Chapel Hill, NC 27599, USA
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10
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Faingold CL, Feng HJ. A unified hypothesis of SUDEP: Seizure-induced respiratory depression induced by adenosine may lead to SUDEP but can be prevented by autoresuscitation and other restorative respiratory response mechanisms mediated by the action of serotonin on the periaqueductal gray. Epilepsia 2023; 64:779-796. [PMID: 36715572 PMCID: PMC10673689 DOI: 10.1111/epi.17521] [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: 10/07/2022] [Revised: 01/20/2023] [Accepted: 01/27/2023] [Indexed: 01/31/2023]
Abstract
Sudden unexpected death in epilepsy (SUDEP) is a major cause of death in people with epilepsy (PWE). Postictal apnea leading to cardiac arrest is the most common sequence of terminal events in witnessed cases of SUDEP, and postconvulsive central apnea has been proposed as a potential biomarker of SUDEP susceptibility. Research in SUDEP animal models has led to the serotonin and adenosine hypotheses of SUDEP. These neurotransmitters influence respiration, seizures, and lethality in animal models of SUDEP, and are implicated in human SUDEP cases. Adenosine released during seizures is proposed to be an important seizure termination mechanism. However, adenosine also depresses respiration, and this effect is mediated, in part, by inhibition of neuronal activity in subcortical structures that modulate respiration, including the periaqueductal gray (PAG). Drugs that enhance the action of adenosine increase postictal death in SUDEP models. Serotonin is also released during seizures, but enhances respiration in response to an elevated carbon dioxide level, which often occurs postictally. This effect of serotonin can potentially compensate, in part, for the adenosine-mediated respiratory depression, acting to facilitate autoresuscitation and other restorative respiratory response mechanisms. A number of drugs that enhance the action of serotonin prevent postictal death in several SUDEP models and reduce postictal respiratory depression in PWE. This effect of serotonergic drugs may be mediated, in part, by actions on brainstem sites that modulate respiration, including the PAG. Enhanced activity in the PAG increases respiration in response to hypoxia and other exigent conditions and can be activated by electrical stimulation. Thus, we propose the unifying hypothesis that seizure-induced adenosine release leads to respiratory depression. This can be reversed by serotonergic action on autoresuscitation and other restorative respiratory responses acting, in part, via the PAG. Therefore, we hypothesize that serotonergic or direct activation of this brainstem site may be a useful approach for SUDEP prevention.
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Affiliation(s)
- Carl L Faingold
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois, USA
- Department of Neurology, Southern Illinois University School of Medicine, Springfield, Illinois, USA
| | - Hua-Jun Feng
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Anesthesia, Harvard Medical School, Boston, Massachusetts, USA
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11
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Pathomechanisms of depression in progressive supranuclear palsy. J Neural Transm (Vienna) 2023:10.1007/s00702-023-02621-w. [PMID: 36933007 DOI: 10.1007/s00702-023-02621-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 03/12/2023] [Indexed: 03/19/2023]
Abstract
Depression is one of the most frequent neuropsychiatric symptoms in progressive supranuclear palsy (PSP), a four-repeat tauopathy and most common atypical parkinsonian disorder, but its pathophysiology and pathogenesis are poorly understood. Pubmed/Medline was systematically analyzed until January 2023, with focus on the prevalence, major clinical features, neuroimaging findings and treatment options of depression in PSP. The average prevalence of depression in PSP is around 50%; it does usually not correlate with most other clinical parameters. Depression is associated with multi-regional patterns of morphometric gray matter variations, e.g., reduced thickness of temporo-parieto-occipital cortices, and altered functional orbitofrontal and medial frontal circuits with disturbances of mood-related brain networks. Unfortunately, no specific neuropathological data about depression in PSP are available. Antidepressive and electroconvulsive therapies are effective in improving symptoms; the efficacy of transcranial stimulation needs further confirmation. Depression in PSP is a common symptom, related to multi-regional patterns of cerebral disturbances and complex pathogenic mechanisms that deserve further elucidation as a basis for adequate treatment to improve the quality of life in this fatal disease.
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12
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Zhang XO, Do Monte FH. Positioning the brainstem within the neural network of threat prediction. Trends Neurosci 2023; 46:91-93. [PMID: 36470706 PMCID: PMC9877175 DOI: 10.1016/j.tins.2022.11.004] [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: 11/14/2022] [Accepted: 11/20/2022] [Indexed: 12/05/2022]
Abstract
In a recent study, Strickland and McDannald dissected the role of brainstem networks in threat prediction. Using probabilistic threat discrimination in rats, the authors demonstrated that brainstem neurons estimate threat probability and generate positive aversive prediction errors after unexpected outcomes. Their findings suggest that, beyond organizing defensive behaviors, brainstem neurons are involved in threat prediction computations.
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Affiliation(s)
- Xu O Zhang
- Department of Neurobiology and Anatomy, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Fabricio H Do Monte
- Department of Neurobiology and Anatomy, The University of Texas Health Science Center at Houston, Houston, TX, USA.
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13
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Jellinger KA. Pathomechanisms of depression in multiple system atrophy. J Neural Transm (Vienna) 2023; 130:1-6. [PMID: 36348076 DOI: 10.1007/s00702-022-02560-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 10/20/2022] [Indexed: 11/09/2022]
Abstract
Multiple system atrophy (MSA) is a rapidly progressing neurodegenerative disorder of uncertain etiology that is characterized by various combinations of Parkinsonism, autonomic, cerebellar and motor dysfunctions, with poor prognosis. Little is known about modifiable factors, such as depression, that has negative effects on quality of life in MSA. Depression, with an estimated prevalence of about 43%, is among the most common neuropsychiatric disorders in MSA similar to other atypical Parkinsonian disorders, the frequency of which is associated with increased disease progression, disease severity and autonomic dysfunctions. Depression in MSA, like in Parkinson disease, has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, such as involvement of serotonergic neuron groups in the brainstem, prefrontal cortical dysfunctions, and altered functional fronto-temporal-thalamic connectivities with disturbances of mood related and other essential resting-state brain networks. The pathophysiology and pathogenesis of depression in MSA, as in other degenerative movement disorders, are complex and deserve further elucidation as a basis for adequate treatment to improve the quality of life in this fatal disease.
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Affiliation(s)
- Kurt A Jellinger
- Institute of Clinical Neurobiology, Alberichgasse 5/13, 1150, Vienna, Austria.
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14
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Jellinger KA. The pathobiological basis of depression in Parkinson disease: challenges and outlooks. J Neural Transm (Vienna) 2022; 129:1397-1418. [PMID: 36322206 PMCID: PMC9628588 DOI: 10.1007/s00702-022-02559-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
Depression, with an estimated prevalence of about 40% is a most common neuropsychiatric disorder in Parkinson disease (PD), with a negative impact on quality of life, cognitive impairment and functional disability, yet the underlying neurobiology is poorly understood. Depression in PD (DPD), one of its most common non-motor symptoms, can precede the onset of motor symptoms but can occur at any stage of the disease. Although its diagnosis is based on standard criteria, due to overlap with other symptoms related to PD or to side effects of treatment, depression is frequently underdiagnosed and undertreated. DPD has been related to a variety of pathogenic mechanisms associated with the underlying neurodegenerative process, in particular dysfunction of neurotransmitter systems (dopaminergic, serotonergic and noradrenergic), as well as to disturbances of cortico-limbic, striato-thalamic-prefrontal, mediotemporal-limbic networks, with disruption in the topological organization of functional mood-related, motor and other essential brain network connections due to alterations in the blood-oxygen-level-dependent (BOLD) fluctuations in multiple brain areas. Other hypothetic mechanisms involve neuroinflammation, neuroimmune dysregulation, stress hormones, neurotrophic, toxic or metabolic factors. The pathophysiology and pathogenesis of DPD are multifactorial and complex, and its interactions with genetic factors, age-related changes, cognitive disposition and other co-morbidities awaits further elucidation.
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Affiliation(s)
- Kurt A Jellinger
- Institute of Clinical Neurobiology, Alberichgasse 5/13, 1150, Vienna, Austria.
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15
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Barko K, Shelton M, Xue X, Afriyie-Agyemang Y, Puig S, Freyberg Z, Tseng GC, Logan RW, Seney ML. Brain region- and sex-specific transcriptional profiles of microglia. Front Psychiatry 2022; 13:945548. [PMID: 36090351 PMCID: PMC9448907 DOI: 10.3389/fpsyt.2022.945548] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/15/2022] [Indexed: 02/05/2023] Open
Abstract
Microglia are resident macrophages of the brain, performing roles related to brain homeostasis, including modulation of synapses, trophic support, phagocytosis of apoptotic cells and debris, as well as brain protection and repair. Studies assessing morphological and transcriptional features of microglia found regional differences as well as sex differences in some investigated brain regions. However, markers used to isolate microglia in many previous studies are not expressed exclusively by microglia or cannot be used to identify and isolate microglia in all contexts. Here, fluorescent activated cell sorting was used to isolate cells expressing the microglia-specific marker TMEM119 from prefrontal cortex (PFC), striatum, and midbrain in mice. RNA-sequencing was used to assess the transcriptional profile of microglia, focusing on brain region and sex differences. We found striking brain region differences in microglia-specific transcript expression. Most notable was the distinct transcriptional profile of midbrain microglia, with enrichment for pathways related to immune function; these midbrain microglia exhibited a profile similar to disease-associated or immune-surveillant microglia. Transcripts more highly expressed in PFC isolated microglia were enriched for synapse-related pathways while microglia isolated from the striatum were enriched for pathways related to microtubule polymerization. We also found evidence for a gradient of expression of microglia-specific transcripts across the rostral-to-caudal axes of the brain, with microglia extracted from the striatum exhibiting a transcriptional profile intermediate between that of the PFC and midbrain. We also found sex differences in expression of microglia-specific transcripts in all 3 brain regions, with many selenium-related transcripts more highly expressed in females across brain regions. These results suggest that the transcriptional profile of microglia varies between brain regions under homeostatic conditions, suggesting that microglia perform diverse roles in different brain regions and even based on sex.
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Affiliation(s)
- Kelly Barko
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Micah Shelton
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Xiangning Xue
- Department of Biostatistics, University of Pittsburgh School of Public Health, Pittsburgh, PA, United States
| | - Yvette Afriyie-Agyemang
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
| | - Stephanie Puig
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
- Center for Systems Neuroscience, Boston University, Boston, MA, United States
| | - Zachary Freyberg
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States
| | - George C. Tseng
- Department of Biostatistics, University of Pittsburgh School of Public Health, Pittsburgh, PA, United States
| | - Ryan W. Logan
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
- Center for Systems Neuroscience, Boston University, Boston, MA, United States
- Genome Science Institute, Boston University School of Medicine, Boston, MA, United States
| | - Marianne L. Seney
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA, United States
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16
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Grasing KW, Burnell K, De A. Biphasic reward effects are characteristic of both lorcaserin and drugs of abuse: implications for treatment of substance use disorders. Behav Pharmacol 2022; 33:238-248. [PMID: 35324488 PMCID: PMC9149059 DOI: 10.1097/fbp.0000000000000672] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Lorcaserin is a modestly selective agonist for 2C serotonin receptors (5-HT2CR). Despite early promising data, it recently failed to facilitate cocaine abstinence in patients and has been compared with dopamine antagonist medications (antipsychotics). Here, we review the effects of both classes on drug reinforcement. In addition to not being effective treatments for cocaine use disorder, both dopamine antagonists and lorcaserin can have biphasic effects on dopamine and reward behavior. Lower doses can cause enhanced drug taking with higher doses causing reductions. This biphasic pattern is shared with certain stimulants, opioids, and sedative-hypnotics, as well as compounds without abuse potential that include agonists for muscarinic and melatonin receptors. Additional factors associated with decreased drug taking include intermittent dosing for dopamine antagonists and use of progressive-ratio schedules for lorcaserin. Clinically relevant doses of lorcaserin were much lower than those that inhibited cocaine-reinforced behavior and can also augment this same behavior in different species. Diminished drug-reinforced behavior only occurred in animals after higher doses that are not suitable for use in patients. In conclusion, drugs of abuse and related compounds often act as biphasic modifiers of reward behavior, especially when evaluated over a broad range of doses. This property may reflect the underlying physiology of the reward system, allowing homeostatic influences on behavior.
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Affiliation(s)
- Ken W Grasing
- Substance Use Research Laboratory, Research Service, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri
- Division of Clinical Pharmacology, Department of Medicine, University of Kansas School of Medicine, Kansas City, Kansas, USA
| | - Kim Burnell
- Substance Use Research Laboratory, Research Service, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri
| | - Alok De
- Substance Use Research Laboratory, Research Service, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri
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17
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Hassan AS, Fajardo ME, Cummings M, McPherson LM, Negro F, Dewald JPA, Heckman CJ, Pearcey GEP. Estimates of persistent inward currents are reduced in upper limb motor units of older adults. J Physiol 2021; 599:4865-4882. [PMID: 34505294 DOI: 10.1113/jp282063] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 09/07/2021] [Indexed: 11/08/2022] Open
Abstract
Ageing is a natural process causing alterations in the neuromuscular system, which contributes to reduced quality of life. Motor unit (MU) contributes to weakness, but the mechanisms underlying reduced firing rates are unclear. Persistent inward currents (PICs) are crucial for initiation, gain control and maintenance of motoneuron firing, and are directly proportional to the level of monoaminergic input. Since concentrations of monoamines (i.e. serotonin and noradrenaline) are reduced with age, we sought to determine if estimates of PICs are reduced in older (>60 years old) compared to younger adults (<35 years old). We decomposed MU spike trains from high-density surface electromyography over the biceps and triceps brachii during isometric ramp contractions to 20% of maximum. Estimates of PICs (ΔFrequency; or simply ΔF) were computed using the paired MU analysis technique. Regardless of the muscle, peak firing rates of older adults were reduced by ∼1.6 pulses per second (pps) (P = 0.0292), and ΔF was reduced by ∼1.9 pps (P < 0.0001), compared to younger adults. We further found that age predicted ΔF in older adults (P = 0.0261), resulting in a reduction of ∼1 pps per decade, but there was no relationship in younger adults (P = 0.9637). These findings suggest that PICs are reduced in the upper limbs of older adults during submaximal isometric contractions. Reduced PIC magnitude represents one plausible mechanism for reduced firing rates and function in older individuals, but further work is required to understand the implications in other muscles and during a variety of motor tasks. KEY POINTS: Persistent inward currents play an important role in the neural control of human movement and are influenced by neuromodulation via monoamines originating in the brainstem. During ageing, motor unit firing rates are reduced, and there is deterioration of brainstem nuclei, which may reduce persistent inward currents in alpha motoneurons. Here we show that estimates of persistent inward currents (ΔF) of both elbow flexor and extensor motor units are reduced in older adults. Estimates of persistent inward currents have a negative relationship with age in the older adults, but not in the young. This novel mechanism may play a role in the alteration of motor firing rates that occurs with ageing, which may have consequences for motor control.
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Affiliation(s)
- Altamash S Hassan
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Melissa E Fajardo
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Mark Cummings
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Laura Miller McPherson
- Program in Physical Therapy, Washington University School of Medicine, St Louis, MO, USA.,Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Universita' degli Studi di Brescia, Brescia, Italy
| | - Julius P A Dewald
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - C J Heckman
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Shirley Ryan AbilityLab, Chicago, IL, USA
| | - Gregory E P Pearcey
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Shirley Ryan AbilityLab, Chicago, IL, USA
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