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Wang ZJ, Sun L, Heinbockel T. Firing Patterns of Mitral Cells and Their Transformation in the Main Olfactory Bulb. Brain Sci 2024; 14:678. [PMID: 39061419 DOI: 10.3390/brainsci14070678] [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: 05/31/2024] [Revised: 06/27/2024] [Accepted: 06/28/2024] [Indexed: 07/28/2024] Open
Abstract
Mitral cells (MCs) in the main olfactory bulb relay odor information to higher-order olfactory centers by encoding the information in the form of action potentials. The firing patterns of these cells are influenced by both their intrinsic properties and their synaptic connections within the neural network. However, reports on MC firing patterns have been inconsistent, and the mechanisms underlying these patterns remain unclear. Using whole-cell patch-clamp recordings in mouse brain slices, we discovered that MCs exhibit two types of integrative behavior: regular/rhythmic firing and bursts of action potentials. These firing patterns could be transformed both spontaneously and chemically. MCs with regular firing maintained their pattern even in the presence of blockers of fast synaptic transmission, indicating this was an intrinsic property. However, regular firing could be transformed into bursting by applying GABAA receptor antagonists to block inhibitory synaptic transmission. Burst firing could be reverted to regular firing by blocking ionotropic glutamate receptors, rather than applying a GABAA receptor agonist, indicating that ionotropic glutamatergic transmission mediated this transformation. Further experiments on long-lasting currents (LLCs), which generated burst firing, also supported this mechanism. In addition, cytoplasmic Ca2+ in MCs was involved in the transformation of firing patterns mediated by glutamatergic transmission. Metabotropic glutamate receptors also played a role in LLCs in MCs. These pieces of evidence indicate that odor information can be encoded on a mitral cell (MC) platform, where it can be relayed to higher-order olfactory centers through intrinsic and dendrodendritic mechanisms in MCs.
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Affiliation(s)
- Ze-Jun Wang
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Liqin Sun
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
| | - Thomas Heinbockel
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
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Li Z, Lu G, Luo E, Wu B, Li Z, Guo J, Xia Z, Zheng C, Su Q, Zeng Y, Yee Chan W, Su X, Qiu X, Zheng X, Cai Q, Xu Y, Chen Y, Fan Y, Chen W, Yu Z, Chen X, Zheng C, Wang M, Sang Poon W, Luo X. Oral, Nasal, and Gut Microbiota in Parkinson's Disease. Neuroscience 2021; 480:65-78. [PMID: 34695538 DOI: 10.1016/j.neuroscience.2021.10.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 12/11/2022]
Abstract
Parkinson's disease (PD) is the second most frequently diagnosed neurodegenerative disease. The purpose of this study was to investigate the link between microbiota composition in important mucosal interfaces (oral, nasal, and intestinal) and PD. Sequencing was undertaken of the V4-V5 region of the 16S ribosomal RNA (rRNA) gene of the microbiome from the oral cavity, nasal cavity, and gut of 91 PD patients and 91 healthy controls. Significant differences were found in microbiota composition in the oral cavity and gut, but not the nasal cavity, between PD patients and healthy controls after adjusting for age, gender, and body mass index (BMI). More genera in the oral cavity were significantly positively correlated with clinical characteristics, such as the HAMA and HAMD rating scales. The taxa c_Clostridia, o_Clostridiales, and f_Ruminococcaceae in the gut microbiota were associated with weight and MMSE score. Furthermore, as a result of dysbiosis, there was an enrichment of ion channel-, oxidative phosphorylation-, and carbohydrate metabolism-related pathways in the oral cavity and glycolysis/gluconeogenesis- and propanoate metabolism-related pathways in the intestine. Changes in these pathways can influence metabolism and inflammation, thereby contributing to PD pathogenesis. In addition, several subnetworks containing differentially abundant microbiota in the oral cavity and gut samples from PD patients may regulate microbial composition and function in PD. Overall, our results indicate that oral and gut dysbiosis may affect PD progression and provide a basis for understanding the pathogenesis of PD and identifying potential therapeutic targets for the treatment of this disease.
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Affiliation(s)
- Zhuo Li
- Genetic Testing Lab, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China; Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
| | - Gang Lu
- The Chinese University of Hong Kong-Shandong University (CUHK-SDU) Joint Laboratory on Reproductive Genetics, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
| | - Enli Luo
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Bin Wu
- Genetic Testing Lab, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
| | - Zhe Li
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Jianwen Guo
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Zhangyong Xia
- Department of Neurology, Liaocheng People's Hospital, Liaocheng 252000, Shandong, China; Liaocheng Clinical School of Shandong First Medical University, Liaocheng 252000, Shandong, China
| | - Chunye Zheng
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Qiaozhen Su
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Yan Zeng
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China
| | - Wai Yee Chan
- The Chinese University of Hong Kong-Shandong University (CUHK-SDU) Joint Laboratory on Reproductive Genetics, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
| | - Xianwei Su
- The Chinese University of Hong Kong-Shandong University (CUHK-SDU) Joint Laboratory on Reproductive Genetics, School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China
| | - Xinmin Qiu
- Genetic Testing Lab, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510120, China
| | - Xirun Zheng
- Department of Pathology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510665, China
| | - Qiaodi Cai
- The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Yanjuan Xu
- The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Yingjun Chen
- The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Yuzhen Fan
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China; The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Weiwei Chen
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China; The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Zecheng Yu
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China; The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Xinjie Chen
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China; The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Chunying Zheng
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China; The Second Clinical College of Guangzhou University of Chinese Medicine, Guangzhou 510405, China
| | - Mingbang Wang
- Children's Hospital of Fudan University, National Center for Children's Health, Shanghai 201102, China
| | - Wai Sang Poon
- Division of Neurosurgery, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
| | - Xiaodong Luo
- Department of Neurology, The Second Affiliated Hospital of Guangzhou University of Chinese Medicine, Guangzhou 510370, China.
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Coincidence Detection within the Excitable Rat Olfactory Bulb Granule Cell Spines. J Neurosci 2019; 39:584-595. [PMID: 30674614 DOI: 10.1523/jneurosci.1798-18.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/13/2018] [Accepted: 10/09/2018] [Indexed: 11/21/2022] Open
Abstract
In the mammalian olfactory bulb, the inhibitory axonless granule cells (GCs) feature reciprocal synapses that interconnect them with the principal neurons of the bulb, mitral, and tufted cells. These synapses are located within large excitable spines that can generate local action potentials (APs) upon synaptic input ("spine spike"). Moreover, GCs can fire global APs that propagate throughout the dendrite. Strikingly, local postsynaptic Ca2+ entry summates mostly linearly with Ca2+ entry due to coincident global APs generated by glomerular stimulation, although some underlying conductances should be inactivated. We investigated this phenomenon by constructing a compartmental GC model to simulate the pairing of local and global signals as a function of their temporal separation Δt. These simulations yield strongly sublinear summation of spine Ca2+ entry for the case of perfect coincidence Δt = 0 ms. Summation efficiency (SE) sharply rises for both positive and negative Δt. The SE reduction for coincident signals depends on the presence of voltage-gated Na+ channels in the spine head, while NMDARs are not essential. We experimentally validated the simulated SE in slices of juvenile rat brain (both sexes) by pairing two-photon uncaging of glutamate at spines and APs evoked by somatic current injection at various intervals Δt while imaging spine Ca2+ signals. Finally, the latencies of synaptically evoked global APs and EPSPs were found to correspond to Δt ≈ 10 ms, explaining the observed approximately linear summation of synaptic local and global signals. Our results provide additional evidence for the existence of the GC spine spike.SIGNIFICANCE STATEMENT Here we investigate the interaction of local synaptic inputs and global activation of a neuron by a backpropagating action potential within a dendritic spine with respect to local Ca2+ signaling. Our system of interest, the reciprocal spine of the olfactory bulb granule cell, is known to feature a special processing mode, namely, a synaptically triggered action potential that is restricted to the spine head. Therefore, coincidence detection of local and global signals follows different rules than in more conventional synapses. We unravel these rules using both simulations and experiments and find that signals coincident within ≈±7 ms around 0 ms result in sublinear summation of Ca2+ entry because of synaptic activation of voltage-gated Na+ channels within the spine.
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Saba L, Viscomi MT, Martini A, Caioli S, Mercuri NB, Guatteo E, Zona C. Modified age-dependent expression of NaV1.6 in an ALS model correlates with motor cortex excitability alterations. Neurobiol Dis 2019; 130:104532. [PMID: 31302244 DOI: 10.1016/j.nbd.2019.104532] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 06/28/2019] [Accepted: 07/10/2019] [Indexed: 12/13/2022] Open
Abstract
Cortical hyperexcitability is an early and intrinsic feature of Amyotrophic Lateral Sclerosis (ALS), but the mechanisms underlying this critical neuronal dysfunction are poorly understood. Recently, we have demonstrated that layer V pyramidal neurons (PNs) in the primary motor cortex (M1) of one-month old (P30) G93A ALS mice display an early hyperexcitability status compared to Control mice. In order to investigate the time-dependent evolution of the cortical excitability in the G93A ALS model, here we have performed an electrophysiological and immunohistochemical study at three different mouse ages. M1 PNs from 14-days old (P14) G93A mice have shown no excitability alterations, while M1 PNs from 3-months old (P90) G93A mice have shown a hypoexcitability status, compared to Control mice. These age-dependent cortical excitability dysfunctions correlate with a similar time-dependent trend of the persistent sodium current (INaP) amplitude alterations, suggesting that INaP may play a crucial role in the G93A cortical excitability aberrations. Specifically, immunohistochemistry experiments have indicated that the expression level of the NaV1.6 channel, one of the voltage-gated Na+ channels mainly distributed within the central nervous system, varies in G93A primary motor cortex during disease progression, according to the excitability and INaP alterations, but not in other cortical areas. Microfluorometry experiments, combined with electrophysiological recordings, have verified that P30 G93A PNs hyperexcitability is associated to a greater accumulation of intracellular calcium ([Ca2+]i) compared to Control PNs, and that this difference is still present when G93A and Control PNs fire action potentials at the same frequency. These results suggest that [Ca2+]i de-regulation in G93A PNs may contribute to neuronal demise and that the NaV1.6 channels could be a potential therapeutic target to ameliorate ALS disease progression.
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Affiliation(s)
- Luana Saba
- Department of Systems Medicine, University of Rome "Tor Vergata" via Montpellier 1, Rome 00133, Italy
| | - Maria Teresa Viscomi
- Università Cattolica del Sacro Cuore, Istituto di Istologia ed Embriologia, Fondazione Policlinico Universitario A. Gemelli, Largo F. Vito 1, Rome 00168, Italy
| | - Alessandro Martini
- IRCCS Fondazione Santa Lucia, via del Fosso di Fiorano 64, Rome 00143, Italy
| | - Silvia Caioli
- IRCCS Fondazione Santa Lucia, via del Fosso di Fiorano 64, Rome 00143, Italy
| | - Nicola Biagio Mercuri
- Department of Systems Medicine, University of Rome "Tor Vergata" via Montpellier 1, Rome 00133, Italy; IRCCS Fondazione Santa Lucia, via del Fosso di Fiorano 64, Rome 00143, Italy
| | - Ezia Guatteo
- IRCCS Fondazione Santa Lucia, via del Fosso di Fiorano 64, Rome 00143, Italy; Department of Motor Science and Wellness, University of Naples 'Parthenope', Via Medina 40, Naples 80133, Italy
| | - Cristina Zona
- Department of Systems Medicine, University of Rome "Tor Vergata" via Montpellier 1, Rome 00133, Italy; IRCCS Fondazione Santa Lucia, via del Fosso di Fiorano 64, Rome 00143, Italy.
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Allosteric Modulation of GABAA Receptors by an Anilino Enaminone in an Olfactory Center of the Mouse Brain. Pharmaceuticals (Basel) 2014; 7:1069-90. [PMID: 25525715 PMCID: PMC4276907 DOI: 10.3390/ph7121069] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 11/24/2014] [Accepted: 12/04/2014] [Indexed: 12/28/2022] Open
Abstract
In an ongoing effort to identify novel drugs that can be used as neurotherapeutic compounds, we have focused on anilino enaminones as potential anticonvulsant agents. Enaminones are organic compounds containing a conjugated system of an amine, an alkene and a ketone. Here, we review the effects of a small library of anilino enaminones on neuronal activity. Our experimental approach employs an olfactory bulb brain slice preparation using whole-cell patch-clamp recording from mitral cells in the main olfactory bulb. The main olfactory bulb is a key integrative center in the olfactory pathway. Mitral cells are the principal output neurons of the main olfactory bulb, receiving olfactory receptor neuron input at their dendrites within glomeruli, and projecting glutamatergic axons through the lateral olfactory tract to the olfactory cortex. The compounds tested are known to be effective in attenuating pentylenetetrazol (PTZ) induced convulsions in rodent models. One compound in particular, KRS-5Me-4-OCF3, evokes potent inhibition of mitral cell activity. Experiments aimed at understanding the cellular mechanism underlying the inhibitory effect revealed that KRS-5Me-4-OCF3 shifts the concentration-response curve for GABA to the left. KRS-5Me-4-OCF3 enhances GABA affinity and acts as a positive allosteric modulator of GABAA receptors. Application of a benzodiazepine site antagonist blocks the effect of KRS-5Me-4-OCF3 indicating that KRS-5Me-4-OCF3 binds at the classical benzodiazepine site to exert its pharmacological action. This anilino enaminone KRS-5Me-4-OCF3 emerges as a candidate for clinical use as an anticonvulsant agent in the battle against epileptic seizures.
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D'Souza RD, Parsa PV, Vijayaraghavan S. Nicotinic receptors modulate olfactory bulb external tufted cells via an excitation-dependent inhibitory mechanism. J Neurophysiol 2013; 110:1544-53. [PMID: 23843430 DOI: 10.1152/jn.00865.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Olfactory bulb (OB) glomeruli, the initial sites of synaptic processing of odor information, exhibit high levels of nicotinic acetylcholine receptor (nAChR) expression and receive strong cholinergic input from the basal forebrain. The role of glomerular nAChRs in olfactory processing, however, remains to be elucidated. External tufted (ET) cells are a major source of excitation in the glomerulus and an important component of OB physiology. We have examined the role of nAChRs in modulating ET cell activity using whole-cell electrophysiology in mouse OB slices. We show here that the activation of glomerular nAChRs leads to direct ET cell excitation, as well as an increase in the frequency of spontaneous postsynaptic GABAergic currents. β2-containing nAChRs, likely the α4β2*-nAChR subtype (* represents the possible presence of other subunits), were significant contributors to these effects. The nAChR-mediated increase in spontaneous postsynaptic GABAergic current frequency on ET cells was, for the most part, dependent on glutamate receptor activation, thus implicating a role for excitation-dependent inhibition within the glomerulus. β2-containing nAChRs also regulate the frequency of miniature inhibitory postsynaptic currents on ET cells, implying nicotinic modulation of dendrodendritic signaling between ET and periglomerular cells. Our data also indicate that nAChR activation does not affect spontaneous or evoked transmission at the olfactory nerve-to-ET cell synapse. The results from this study suggest that ET cells, along with mitral cells, play an important role in the nicotinic modulation of glomerular inhibition.
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Affiliation(s)
- Rinaldo D D'Souza
- Department of Physiology and Biophysics and Neuroscience Program, University of Colorado School of Medicine, Aurora, Colorado
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