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Kang J, Lu N, Yang S, Guo B, Zhu Y, Wu S, Huang X, Wong-Riley MTT, Liu YY. Alterations in synapses and mitochondria induced by acute or chronic intermittent hypoxia in the pre-Bötzinger complex of rats: an ultrastructural triple-labeling study with immunocytochemistry and histochemistry. Front Cell Neurosci 2023; 17:1132241. [PMID: 37396926 PMCID: PMC10312010 DOI: 10.3389/fncel.2023.1132241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 06/05/2023] [Indexed: 07/04/2023] Open
Abstract
Introduction The pre-Bötzinger complex (pre-BötC), a kernel of inspiratory rhythmogenesis, is a heterogeneous network with excitatory glutamatergic and inhibitory GABAergic and glycinergic neurons. Inspiratory rhythm generation relies on synchronous activation of glutamatergic neuron, whilst inhibitory neurons play a critical role in shaping the breathing pattern, endowing the rhythm with flexibility in adapting to environmental, metabolic, and behavioral needs. Here we report ultrastructural alterations in excitatory, asymmetric synapses (AS) and inhibitory, symmetric synapses (SS), especially perforated synapses with discontinuous postsynaptic densities (PSDs) in the pre-BötC in rats exposed to daily acute intermittent hypoxia (dAIH) or chronic (C) IH. Methods We utilized for the first time a combination of somatostatin (SST) and neurokinin 1 receptor (NK1R) double immunocytochemistry with cytochrome oxidase histochemistry, to reveal synaptic characteristics and mitochondrial dynamic in the pre-BötC. Results We found perforated synapses with synaptic vesicles accumulated in distinct pools in apposition to each discrete PSD segments. dAIH induced significant increases in the PSD size of macular AS, and the proportion of perforated synapses. AS were predominant in the dAIH group, whereas SS were in a high proportion in the CIH group. dAIH significantly increased SST and NK1R expressions, whereas CIH led to a decrease. Desmosome-like contacts (DLC) were characterized for the first time in the pre-BötC. They were distributed alongside of synapses, especially SS. Mitochondria appeared in more proximity to DLC than synapses, suggestive of a higher energy demand of the DLC. Findings of single spines with dual AS and SS innervation provide morphological evidence of excitation-inhibition interplay within a single spine in the pre-BötC. In particular, we characterized spine-shaft microdomains of concentrated synapses coupled with mitochondrial positioning that could serve as a structural basis for synchrony of spine-shaft communication. Mitochondria were found within spines and ultrastructural features of mitochondrial fusion and fission were depicted for the first time in the pre-BötC. Conclusion We provide ultrastructural evidence of excitation-inhibition synapses in shafts and spines, and DLC in association with synapses that coincide with mitochondrial dynamic in their contribution to respiratory plasticity in the pre-BötC.
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Affiliation(s)
- Junjun Kang
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Naining Lu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Shoujing Yang
- Department of Pathology, The Fourth Military Medical University, Xi’an, China
| | - Baolin Guo
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Yuanyuan Zhu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Shengxi Wu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
| | - Xiaofeng Huang
- Department of Pathology, Xi’an Gaoxin Hospital, Xi’an, China
| | - Margaret T. T. Wong-Riley
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Ying-Ying Liu
- Department of Neurobiology, The Fourth Military Medical University, Xi’an, China
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2
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Patodia S, Somani A, Thom M. Review: Neuropathology findings in autonomic brain regions in SUDEP and future research directions. Auton Neurosci 2021; 235:102862. [PMID: 34411885 PMCID: PMC8455454 DOI: 10.1016/j.autneu.2021.102862] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 07/16/2021] [Accepted: 07/24/2021] [Indexed: 12/21/2022]
Abstract
Autonomic dysfunction is implicated from clinical, neuroimaging and experimental studies in sudden and unexpected death in epilepsy (SUDEP). Neuropathological analysis in SUDEP series enable exploration of acquired, seizure-related cellular adaptations in autonomic and brainstem autonomic centres of relevance to dysfunction in the peri-ictal period. Alterations in SUDEP compared to control groups have been identified in the ventrolateral medulla, amygdala, hippocampus and central autonomic regions. These involve neuropeptidergic, serotonergic and adenosine systems, as well as specific regional astroglial and microglial populations, as potential neuronal modulators, orchestrating autonomic dysfunction. Future research studies need to extend to clinically and genetically characterized epilepsies, to explore if common or distinct pathways of autonomic dysfunction mediate SUDEP. The ultimate objective of SUDEP research is the identification of disease biomarkers for at risk patients, to improve post-mortem recognition and disease categorisation, but ultimately, for exposing potential treatment targets of pharmacologically modifiable and reversible cellular alterations.
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Affiliation(s)
- Smriti Patodia
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Alyma Somani
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK
| | - Maria Thom
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London WC1N 3BG, UK.
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Somatostatin, a Presynaptic Modulator of Glutamatergic Signal in the Central Nervous System. Int J Mol Sci 2021; 22:ijms22115864. [PMID: 34070785 PMCID: PMC8198526 DOI: 10.3390/ijms22115864] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/19/2021] [Accepted: 05/26/2021] [Indexed: 01/07/2023] Open
Abstract
Somatostatin is widely diffused in the central nervous system, where it participates to control the efficiency of synaptic transmission. This peptide mainly colocalizes with GABA, in inhibitory, GABA-containing interneurons from which it is actively released in a Ca2+ dependent manner upon application of depolarizing stimuli. Once released in the synaptic cleft, somatostatin acts locally, or it diffuses in the extracellular space through "volume diffusion", a mechanism(s) of distribution which mainly operates in the cerebrospinal fluid and that assures the progression of neuronal signalling from signal-secreting sender structures towards receptor-expressing targeted neurons located extrasynaptically, in a non-synaptic, inter-neuronal form of communication. Somatostatin controls the efficiency of central glutamate transmission by either modulating presynaptically the glutamate exocytosis or by metamodulating the activity of glutamate receptors colocalized and functionally coupled with somatostatin receptors in selected subpopulations of nerve terminals. Deciphering the role of somatostatin in the mechanisms of "volume diffusion" and in the "receptor-receptor interaction" unveils new perspectives in the central role of this fine tuner of synaptic strength, paving the road to new therapeutic approaches for the cure of central disorders.
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Varga AG, Maletz SN, Bateman JT, Reid BT, Levitt ES. Neurochemistry of the Kölliker-Fuse nucleus from a respiratory perspective. J Neurochem 2020; 156:16-37. [PMID: 32396650 DOI: 10.1111/jnc.15041] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/27/2020] [Accepted: 05/04/2020] [Indexed: 12/11/2022]
Abstract
The Kölliker-Fuse nucleus (KF) is a functionally distinct component of the parabrachial complex, located in the dorsolateral pons of mammals. The KF has a major role in respiration and upper airway control. A comprehensive understanding of the KF and its contributions to respiratory function and dysfunction requires an appreciation for its neurochemical characteristics. The goal of this review is to summarize the diverse neurochemical composition of the KF, focusing on the neurotransmitters, neuromodulators, and neuropeptides present. We also include a description of the receptors expressed on KF neurons and transporters involved in each system, as well as their putative roles in respiratory physiology. Finally, we provide a short section reviewing the literature regarding neurochemical changes in the KF in the context of respiratory dysfunction observed in SIDS and Rett syndrome. By over-viewing the current literature on the neurochemical composition of the KF, this review will serve to aid a wide range of topics in the future research into the neural control of respiration in health and disease.
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Affiliation(s)
- Adrienn G Varga
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Sebastian N Maletz
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Jordan T Bateman
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
| | - Brandon T Reid
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
| | - Erica S Levitt
- Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA.,Department of Physical Therapy, Center for Respiratory Research and Rehabilitation, University of Florida, Gainesville, FL, USA
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Saleeba C, Dempsey B, Le S, Goodchild A, McMullan S. A Student's Guide to Neural Circuit Tracing. Front Neurosci 2019; 13:897. [PMID: 31507369 PMCID: PMC6718611 DOI: 10.3389/fnins.2019.00897] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 08/12/2019] [Indexed: 12/17/2022] Open
Abstract
The mammalian nervous system is comprised of a seemingly infinitely complex network of specialized synaptic connections that coordinate the flow of information through it. The field of connectomics seeks to map the structure that underlies brain function at resolutions that range from the ultrastructural, which examines the organization of individual synapses that impinge upon a neuron, to the macroscopic, which examines gross connectivity between large brain regions. At the mesoscopic level, distant and local connections between neuronal populations are identified, providing insights into circuit-level architecture. Although neural tract tracing techniques have been available to experimental neuroscientists for many decades, considerable methodological advances have been made in the last 20 years due to synergies between the fields of molecular biology, virology, microscopy, computer science and genetics. As a consequence, investigators now enjoy an unprecedented toolbox of reagents that can be directed against selected subpopulations of neurons to identify their efferent and afferent connectomes. Unfortunately, the intersectional nature of this progress presents newcomers to the field with a daunting array of technologies that have emerged from disciplines they may not be familiar with. This review outlines the current state of mesoscale connectomic approaches, from data collection to analysis, written for the novice to this field. A brief history of neuroanatomy is followed by an assessment of the techniques used by contemporary neuroscientists to resolve mesoscale organization, such as conventional and viral tracers, and methods of selecting for sub-populations of neurons. We consider some weaknesses and bottlenecks of the most widely used approaches for the analysis and dissemination of tracing data and explore the trajectories that rapidly developing neuroanatomy technologies are likely to take.
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Affiliation(s)
- Christine Saleeba
- Neurobiology of Vital Systems Node, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
- The School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Bowen Dempsey
- CNRS, Hindbrain Integrative Neurobiology Laboratory, Neuroscience Paris-Saclay Institute (Neuro-PSI), Université Paris-Saclay, Gif-sur-Yvette, France
| | - Sheng Le
- Neurobiology of Vital Systems Node, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Ann Goodchild
- Neurobiology of Vital Systems Node, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Simon McMullan
- Neurobiology of Vital Systems Node, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
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Kommajosyula SP, Faingold CL. Neural activity in the periaqueductal gray and other specific subcortical structures is enhanced when a selective serotonin reuptake inhibitor selectively prevents seizure-induced sudden death in the DBA/1 mouse model of sudden unexpected death in epilepsy. Epilepsia 2019; 60:1221-1233. [PMID: 31056750 DOI: 10.1111/epi.14759] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Sudden unexpected death in epilepsy (SUDEP) is a critical issue in epilepsy, and DBA/1 mice are a useful animal model of this devastating epilepsy sequela. The serotonin hypothesis for SUDEP proposes that modifying serotonergic function significantly alters susceptibility to seizure-induced respiratory arrest (S-IRA). Agents that enhance serotonergic function, including a selective serotonin reuptake inhibitor, fluoxetine, selectively prevent S-IRA in DBA/1 mice. This study examined fluoxetine-induced changes in brain activity using manganese-enhanced magnetic resonance imaging (MEMRI) to reveal sites in the DBA/1 mouse brain where fluoxetine acts to prevent S-IRA. METHODS DBA/1 mice were subjected to audiogenic seizures (Sz) after saline or fluoxetine (45 mg/kg, intraperitoneal) administration. Control DBA/1 mice received fluoxetine or saline, but Sz were not evoked. A previous MEMRI study established the regions of interest (ROIs) for Sz in the DBA/1 mouse brain, and the present study examined MEMRI differences in the ROIs of these mouse groups. RESULTS The neural activity in several ROIs was significantly increased in fluoxetine-treated DBA/1 mice that exhibited Sz but not S-IRA when compared to the saline-treated mice that exhibited both Sz and respiratory arrest. These structures included the periaqueductal gray (PAG), amygdala, reticular formation (sensorimotor-limbic network), Kölliker-Fuse nucleus, facial-parafacial group (respiratory network), and pontine raphe. Of these ROIs, only the PAG showed significantly decreased neural activity with saline pretreatment when seizure-induced respiratory arrest occurred as compared to saline treatment without seizure. SIGNIFICANCE The PAG is known to play an important compensatory role for respiratory distress caused by numerous exigent situations in normal animals. The pattern of fluoxetine-induced activity changes in the present study suggests that PAG may be the most critical target for fluoxetine's action to prevent seizure-induced sudden death. These findings have potential clinical importance, because there is evidence of anomalous serotonergic function and PAG imaging abnormalities in human SUDEP.
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Affiliation(s)
- Srinivasa P Kommajosyula
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, Illinois
| | - Carl L Faingold
- Departments of Pharmacology and Neurology, Southern Illinois University School of Medicine, Springfield, Illinois
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Bowman BR, Bokiniec P, McMullan S, Goodchild AK, Burke PGR. Somatostatin 2 Receptors in the Spinal Cord Tonically Restrain Thermogenic, Cardiac and Other Sympathetic Outflows. Front Neurosci 2019; 13:121. [PMID: 30842723 PMCID: PMC6391348 DOI: 10.3389/fnins.2019.00121] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 02/04/2019] [Indexed: 12/25/2022] Open
Abstract
The anatomical and functional characterization of somatostatin (SST) and somatostatin receptors (SSTRs) within the spinal cord have been focused in the dorsal horn, specifically in relation to sensory afferent processing. However, SST is also present within the intermediolateral cell column (IML), which contains sympathetic preganglionic neurons (SPN). We investigated the distribution of SSTR2 within the thoracic spinal cord and show that SSTR2A and SSTR2B are expressed in the dorsal horn and on SPN and non-SPN in or near the IML. The effects of activating spinal SSTR and SSTR2 were sympathoinhibition, hypotension, bradycardia, as well as decreases in interscapular brown adipose tissue temperature and expired CO2, in keeping with the well-described inhibitory effects of activating SSTR receptors. These data indicate that spinal SST can decrease sympathetic, cardiovascular and thermogenic activities. Unexpectedly blockade of SSTR2 revealed that SST tonically mantains sympathetic, cardiovascular and thermogenic functions, as activity in all measured parameters increased. In addition, high doses of two antagonists evoked biphasic responses in sympathetic and cardiovascular outflows where the initial excitatory effects were followed by profound but transient falls in sympathetic nerve activity, heart rate and blood pressure. These latter effects, together with our findings that SSTR2A are expressed on GABAergic, presumed interneurons, are consistent with the idea that SST2R tonically influence a diffuse spinal GABAergic network that regulates the sympathetic cardiovascular outflow. As described here and elsewhere the source of tonically released spinal SST may be of intra- and/or supra-spinal origin.
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Affiliation(s)
- Belinda R Bowman
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Phillip Bokiniec
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia.,Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Simon McMullan
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Ann K Goodchild
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia
| | - Peter G R Burke
- Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, Sydney, NSW, Australia.,Neuroscience Research Australia, Sydney, NSW, Australia
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Riedemann T, Sutor B. Long-lasting actions of somatostatin on pyramidal cell excitability in the mouse cingulate cortex. Neurosci Lett 2019; 698:217-223. [PMID: 30668961 DOI: 10.1016/j.neulet.2019.01.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 01/10/2019] [Accepted: 01/18/2019] [Indexed: 02/07/2023]
Abstract
Many neurological diseases are related to disturbances of somatostatin- (SOM-) expressing interneurons in the cingulate cortex. Therefore, their role within the circuitry of the cingulate cortex needs to be investigated. We describe here the physiological time course of SOM effects onto pyramidal cell excitability and action potential discharge pattern. Furthermore, we show that the GRK2 inhibitor Gallein had no effect on the reduced SOM-induced response following repetitive SOM applications.
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Affiliation(s)
- Therese Riedemann
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany.
| | - Bernd Sutor
- Biomedical Center, Ludwig-Maximilians-Universität, Physiological Genomics, Großhaderner Str. 9, 82152 Planegg-Martinsried, Germany
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Lambert GA, Zagami AS. Does somatostatin have a role to play in migraine headache? Neuropeptides 2018; 69:1-8. [PMID: 29751998 DOI: 10.1016/j.npep.2018.04.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/05/2018] [Accepted: 04/15/2018] [Indexed: 11/24/2022]
Abstract
Migraine is a condition without apparent pathology. Its cardinal symptom is the prolonged excruciating headache. Theories about this pain have posited pathologies which run the gamut from neural to vascular to neurovascular, but no observations have detected a plausible pathology. We believe that no pathology can be found for migraine headache because none exists. Migraine is not driven by pathology - it is driven by neural events produced by triggers - or simply by neural noise- noise that has crossed a critical threshold. If these ideas are true, how does the pain arise? We hypothesise that migraine headache is a consequence of withdrawal of descending pain control, produced by "noise" in the cerebral cortex. Nevertheless, there has to be a neural circuit to transform cortical noise to withdrawal of pain control. In our hypothesis, this neural circuit extends from the cortex, synapses in two brainstem nuclei (the periaqueductal gray matter and the raphe magnus nucleus) and ultimately reaches the first synapse of the trigeminal sensory system. The second stage of this circuit uses serotonin (5HT) as a neurotransmitter, but the neuronal projection from the cortex to the brainstem seems to involve relatively uncommon neurotransmitters. We believe that one of these is somatostatin (SST). Temporal changes in levels of circulating SST mirror the temporal changes in the incidence of migraine, particularly in women. The SST2 receptor agonist octreotide has been used with some success in migraine and cluster headache. A cortical to PAG/NRM neural projection certainly exists and we briefly review the anatomical and neurophysiological evidence for it and provide preliminary evidence that SST may the critical neurotransmitter in this pathway. We therefore suggest that the withdrawal of descending tone in SST-containing neurons, might create a false pain signal and hence the headache of migraine.
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Affiliation(s)
- Geoffrey A Lambert
- Prince of Wales Clinical School, UNSW, Australia; School of Medicine, University of Western Sydney, Australia.
| | - Alessandro S Zagami
- Prince of Wales Clinical School, UNSW, Australia; Institute of Neurological Sciences, Prince of Wales Hospital, Australia
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Somatostatin 2 Receptor Activation in the Rostral Ventrolateral Medulla Does Not Mediate the Decompensatory Phase of Haemorrhage. Shock 2017; 50:331-338. [PMID: 28991052 DOI: 10.1097/shk.0000000000001011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Decompensation, a critical phase in the response to hemorrhage, is characterized by profound sympathoinhibition and the overriding of baroreflex mediated compensation. As sympathoexcitatory neurons of the rostral ventrolateral medulla (RVLM) maintain vasomotor tone and are essential for sympathetic baroreceptor reflex function, the RVLM is the likely mediator. However, how decompensation occurs is a mystery. Our previous work demonstrated that the inhibitory neuropeptide somatostatin (SST), evokes potent sympathoinhibition. Here we test the hypothesis that, in response to hypovolemia, SST in the RVLM evokes sympathoinhibition, driving decompensation and suppressing baroreflex compensation. We evaluated neuronal activation at sites that contain SST mRNA and project to the RVLM and, in SST2A expressing neurons in the RVLM. We determined the effects on cardiovascular and sympathetic responses to haemorrhage, of bilateral blockade of SST2 receptors in both the RVLM and A1 regions. Haemorrhage in conscious rats evoked c-Fos immunoreactivity in the amygdala, periaqueductal gray, and parabrachial nuclei, regions previously associated with hemorrhage, shown to contain SST and project to the RVLM. Although c-Fos labeling was found throughout the ventrolateral medulla, only a small subset of RVLM SST2A receptor expressing neurons were activated, consistent with the idea that these neurons are inhibited during hemorrhage. However, SST2 receptor antagonists bilaterally injected in the RVLM or the A1 region did not affect the decompensation response to hemorrhage. Thus somatostatin in the RVLM does not mediate decompensation. The physiological role associated with somatostatin-induced sympathoinhibition in the RVLM together with the central mechanisms responsible for decompensation remain elusive.
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Polysialic Acid Regulates Sympathetic Outflow by Facilitating Information Transfer within the Nucleus of the Solitary Tract. J Neurosci 2017; 37:6558-6574. [PMID: 28576943 DOI: 10.1523/jneurosci.0200-17.2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 05/15/2017] [Accepted: 05/25/2017] [Indexed: 02/07/2023] Open
Abstract
Expression of the large extracellular glycan, polysialic acid (polySia), is restricted in the adult, to brain regions exhibiting high levels of plasticity or remodeling, including the hippocampus, prefrontal cortex, and the nucleus of the solitary tract (NTS). The NTS, located in the dorsal brainstem, receives constant viscerosensory afferent traffic as well as input from central regions controlling sympathetic nerve activity, respiration, gastrointestinal functions, hormonal release, and behavior. Our aims were to determine the ultrastructural location of polySia in the NTS and the functional effects of enzymatic removal of polySia, both in vitro and in vivo polySia immunoreactivity was found throughout the adult rat NTS. Electron microscopy demonstrated polySia at sites that influence neurotransmission: the extracellular space, fine astrocytic processes, and neuronal terminals. Removing polySia from the NTS had functional consequences. Whole-cell electrophysiological recordings revealed altered intrinsic membrane properties, enhancing voltage-gated K+ currents and increasing intracellular Ca2+ Viscerosensory afferent processing was also disrupted, dampening low-frequency excitatory input and potentiating high-frequency sustained currents at second-order neurons. Removal of polySia in the NTS of anesthetized rats increased sympathetic nerve activity, whereas functionally related enzymes that do not alter polySia expression had little effect. These data indicate that polySia is required for the normal transmission of information through the NTS and that changes in its expression alter sympathetic outflow. polySia is abundant in multiple but discrete brain regions, including sensory nuclei, in both the adult rat and human, where it may regulate neuronal function by mechanisms identified here.SIGNIFICANCE STATEMENT All cells are coated in glycans (sugars) existing predominantly as glycolipids, proteoglycans, or glycoproteins formed by the most complex form of posttranslational modification, glycosylation. How these glycans influence brain function is only now beginning to be elucidated. The adult nucleus of the solitary tract has abundant polysialic acid (polySia) and is a major site of integration, receiving viscerosensory information which controls critical homeostatic functions. Our data reveal that polySia is a determinant of neuronal behavior and excitatory transmission in the nucleus of the solitary tract, regulating sympathetic nerve activity. polySia is abundantly expressed at distinct brain sites in adult, including major sensory nuclei, suggesting that sensory transmission may also be influenced via mechanisms described here. These findings hint at the importance of elucidating how other glycans influence neural function.
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Stengel A, Taché YF. Activation of Brain Somatostatin Signaling Suppresses CRF Receptor-Mediated Stress Response. Front Neurosci 2017; 11:231. [PMID: 28487631 PMCID: PMC5403923 DOI: 10.3389/fnins.2017.00231] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 04/06/2017] [Indexed: 12/30/2022] Open
Abstract
Corticotropin-releasing factor (CRF) is the hallmark brain peptide triggering the response to stress and mediates—in addition to the stimulation of the hypothalamus-pituitary-adrenal (HPA) axis—other hormonal, behavioral, autonomic and visceral components. Earlier reports indicate that somatostatin-28 injected intracerebroventricularly counteracts the acute stress-induced ACTH and catecholamine release. Mounting evidence now supports that activation of brain somatostatin signaling exerts a broader anti-stress effect by blunting the endocrine, autonomic, behavioral (with a focus on food intake) and visceral gastrointestinal motor responses through the involvement of distinct somatostatin receptor subtypes.
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Affiliation(s)
- Andreas Stengel
- Division of Psychosomatic Medicine, Charité Center for Internal Medicine and Dermatology, Charité-Universitätsmedizin BerlinBerlin, Germany
| | - Yvette F Taché
- Vatche and Tamar Manoukian Digestive Diseases Division, CURE Digestive Diseases Research Center, G Oppenheimer Center for Neurobiology of Stress and Resilience, Department of Medicine, University of California, Los AngelesLos Angeles, CA, USA.,VA Greater Los Angeles Health Care SystemLos Angeles, CA, USA
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13
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Dempsey B, Le S, Turner A, Bokiniec P, Ramadas R, Bjaalie JG, Menuet C, Neve R, Allen AM, Goodchild AK, McMullan S. Mapping and Analysis of the Connectome of Sympathetic Premotor Neurons in the Rostral Ventrolateral Medulla of the Rat Using a Volumetric Brain Atlas. Front Neural Circuits 2017; 11:9. [PMID: 28298886 PMCID: PMC5331070 DOI: 10.3389/fncir.2017.00009] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 02/06/2017] [Indexed: 01/27/2023] Open
Abstract
Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) play a critical role in the generation of vasomotor sympathetic tone and are thought to receive convergent input from neurons at every level of the neuraxis; the factors that determine their ongoing activity remain unresolved. In this study we use a genetically restricted viral tracing strategy to definitively map their spatially diffuse connectome. We infected bulbospinal RVLM neurons with a recombinant rabies variant that drives reporter expression in monosynaptically connected input neurons and mapped their distribution using an MRI-based volumetric atlas and a novel image alignment and visualization tool that efficiently translates the positions of neurons captured in conventional photomicrographs to Cartesian coordinates. We identified prominent inputs from well-established neurohumoral and viscero-sympathetic sensory actuators, medullary autonomic and respiratory subnuclei, and supramedullary autonomic nuclei. The majority of inputs lay within the brainstem (88–94%), and included putative respiratory neurons in the pre-Bötzinger Complex and post-inspiratory complex that are therefore likely to underlie respiratory-sympathetic coupling. We also discovered a substantial and previously unrecognized input from the region immediately ventral to nucleus prepositus hypoglossi. In contrast, RVLM sympathetic premotor neurons were only sparsely innervated by suprapontine structures including the paraventricular nucleus, lateral hypothalamus, periaqueductal gray, and superior colliculus, and we found almost no evidence of direct inputs from the cortex or amygdala. Our approach can be used to quantify, standardize and share complete neuroanatomical datasets, and therefore provides researchers with a platform for presentation, analysis and independent reanalysis of connectomic data.
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Affiliation(s)
- Bowen Dempsey
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Sheng Le
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Anita Turner
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Phil Bokiniec
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Radhika Ramadas
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Jan G Bjaalie
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo Oslo, Norway
| | - Clement Menuet
- Department of Physiology, University of Melbourne Melbourne, VIC, Australia
| | - Rachael Neve
- Viral Core Facility, McGovern Institute for Brain Research, Massachusetts Institute of Technology Cambridge, MA, USA
| | - Andrew M Allen
- Department of Physiology, University of Melbourne Melbourne, VIC, Australia
| | - Ann K Goodchild
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
| | - Simon McMullan
- Faculty of Medicine and Health Sciences, Neurobiology of Vital Systems, Macquarie University Sydney, NSW, Australia
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14
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Entwisle B, McMullan S, Bokiniec P, Gross S, Chung R, Withford M. In vitro neuronal depolarization and increased synaptic activity induced by infrared neural stimulation. BIOMEDICAL OPTICS EXPRESS 2016; 7:3211-3219. [PMID: 27699093 PMCID: PMC5030005 DOI: 10.1364/boe.7.003211] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 06/07/2016] [Accepted: 07/14/2016] [Indexed: 05/11/2023]
Abstract
Neuronal responses to infrared neural stimulation (INS) are explored at the single cell level using patch-clamp electrophysiology. We examined membrane and synaptic responses of solitary tract neurons recorded in acute slices prepared from the Sprague-Dawley rat. Neurons were stimulated using a compact 1890 nm waveguide laser with light delivered to a small target area, comparable to the size of a single cell, via a single-mode fiber. We show that infrared radiation increased spontaneous synaptic event frequency, and evoked steady-state currents and neuronal depolarization. The magnitude of the responses was proportional to laser output.
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Affiliation(s)
- Blake Entwisle
- Department of Physics and Astronomy, Faculty of Science and Engineering, Macquarie University, Australia Centre for Ultrahigh bandwidth Devices for Optical Systems,
Australia
| | - Simon McMullan
- Australian School of Advanced Medicine, Faculty of Human Sciences, Macquarie University,
Australia
| | - Phillip Bokiniec
- Australian School of Advanced Medicine, Faculty of Human Sciences, Macquarie University,
Australia
| | - Simon Gross
- Department of Physics and Astronomy, Faculty of Science and Engineering, Macquarie University, Australia Centre for Ultrahigh bandwidth Devices for Optical Systems,
Australia
| | - Roger Chung
- Australian School of Advanced Medicine, Faculty of Human Sciences, Macquarie University,
Australia
| | - Michael Withford
- Department of Physics and Astronomy, Faculty of Science and Engineering, Macquarie University, Australia Centre for Ultrahigh bandwidth Devices for Optical Systems,
Australia
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