1
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Kofler M, Hallett M, Iannetti GD, Versace V, Ellrich J, Téllez MJ, Valls-Solé J. The blink reflex and its modulation - Part 1: Physiological mechanisms. Clin Neurophysiol 2024; 160:130-152. [PMID: 38102022 PMCID: PMC10978309 DOI: 10.1016/j.clinph.2023.11.015] [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: 07/09/2023] [Revised: 11/11/2023] [Accepted: 11/22/2023] [Indexed: 12/17/2023]
Abstract
The blink reflex (BR) is a protective eye-closure reflex mediated by brainstem circuits. The BR is usually evoked by electrical supraorbital nerve stimulation but can be elicited by a variety of sensory modalities. It has a long history in clinical neurophysiology practice. Less is known, however, about the many ways to modulate the BR. Various neurophysiological techniques can be applied to examine different aspects of afferent and efferent BR modulation. In this line, classical conditioning, prepulse and paired-pulse stimulation, and BR elicitation by self-stimulation may serve to investigate various aspects of brainstem connectivity. The BR may be used as a tool to quantify top-down modulation based on implicit assessment of the value of blinking in a given situation, e.g., depending on changes in stimulus location and probability of occurrence. Understanding the role of non-nociceptive and nociceptive fibers in eliciting a BR is important to get insight into the underlying neural circuitry. Finally, the use of BRs and other brainstem reflexes under general anesthesia may help to advance our knowledge of the brainstem in areas not amenable in awake intact humans. This review summarizes talks held by the Brainstem Special Interest Group of the International Federation of Clinical Neurophysiology at the International Congress of Clinical Neurophysiology 2022 in Geneva, Switzerland, and provides a state-of-the-art overview of the physiology of BR modulation. Understanding the principles of BR modulation is fundamental for a valid and thoughtful clinical application (reviewed in part 2) (Gunduz et al., submitted).
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Affiliation(s)
- Markus Kofler
- Department of Neurology, Hochzirl Hospital, Zirl, Austria.
| | - Mark Hallett
- National Institute of Neurological Disorders and Stroke, NIH, USA.
| | - Gian Domenico Iannetti
- University College London, United Kingdom; Italian Institute of Technology (IIT), Rome, Italy.
| | - Viviana Versace
- Department of Neurorehabilitation, Hospital of Vipiteno (SABES-ASDAA), Teaching Hospital of the Paracelsus Medical Private University (PMU), Vipiteno-Sterzing, Italy.
| | - Jens Ellrich
- Friedrich-Alexander-University Erlangen-Nuremberg, Germany.
| | | | - Josep Valls-Solé
- IDIBAPS (Institut d'Investigació August Pi i Sunyer), University of Barcelona, Spain.
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2
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Baron M, Devor M. From molecule to oblivion: dedicated brain circuitry underlies anesthetic loss of consciousness permitting pain-free surgery. Front Mol Neurosci 2023; 16:1197304. [PMID: 37305550 PMCID: PMC10248014 DOI: 10.3389/fnmol.2023.1197304] [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: 03/30/2023] [Accepted: 05/04/2023] [Indexed: 06/13/2023] Open
Abstract
The canonical view of how general anesthetics induce loss-of-consciousness (LOC) permitting pain-free surgery posits that anesthetic molecules, distributed throughout the CNS, suppress neural activity globally to levels at which the cerebral cortex can no longer sustain conscious experience. We support an alternative view that LOC, in the context of GABAergic anesthesia at least, results from anesthetic exposure of a small number of neurons in a focal brainstem nucleus, the mesopontine tegmental anesthesia area (MPTA). The various sub-components of anesthesia, in turn, are effected in distant locations, driven by dedicated axonal pathways. This proposal is based on the observations that microinjection of infinitesimal amounts of GABAergic agents into the MPTA, and only there, rapidly induces LOC, and that lesioning the MPTA renders animals relatively insensitive to these agents delivered systemically. Recently, using chemogenetics, we identified a subpopulation of MPTA "effector-neurons" which, when excited (not inhibited), induce anesthesia. These neurons contribute to well-defined ascending and descending axonal pathways each of which accesses a target region associated with a key anesthetic endpoint: atonia, anti-nociception, amnesia and LOC (by electroencephalographic criteria). Interestingly, the effector-neurons do not themselves express GABAA-receptors. Rather, the target receptors reside on a separate sub-population of presumed inhibitory interneurons. These are thought to excite the effectors by disinhibition, thus triggering anesthetic LOC.
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Affiliation(s)
- Mark Baron
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Marshall Devor
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- Center for Research on Pain, The Hebrew University of Jerusalem, Jerusalem, Israel
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3
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Anesthetic loss of consciousness induced by chemogenetic excitation of mesopontine effector neurons. Exp Neurol 2022; 357:114169. [PMID: 35817130 DOI: 10.1016/j.expneurol.2022.114169] [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: 02/10/2022] [Revised: 05/22/2022] [Accepted: 07/05/2022] [Indexed: 11/23/2022]
Abstract
Although general anesthesia is normally induced by systemic dosing, an anesthetic state can be induced in rodents by microinjecting minute quantities of GABAergic agents into the brainstem mesopontine tegmental anesthesia area (MPTA). Correspondingly, lesions to the MPTA render rats relatively insensitive to standard anesthetic doses delivered systemically. Using a chemogenetic approach we have identified and characterized a small subpopulation of neurons restricted to the MPTA which, when excited, render the animal anesthetic by sensorimotor (immobility) and electroencephalographic (EEG) criteria. These "effector-neurons" do not express GABAAδ-Rs, the likely target of GABAergic anesthetics. Rather, we report a distinct sub-population of nearby MPTA neurons which do. During anesthetic induction these likely excite the effector-neurons by disinhibition. Within the effector population ~ 70% appear to be glutamatergic, ~30% GABAergic and ~ 40% glycinergic. Most are projection neurons that send ascending or descending axons to distant targets associated with the individual functional components of general anesthesia: atonia, analgesia, amnesia, and loss-of-consciousness.
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4
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Yatziv SL, Yudco O, Vaso K, Mizrahi A, Devor M. Anesthesia in mice activates discrete populations of neurons throughout the brain. J Neurosci Res 2021; 99:3284-3305. [PMID: 34510528 DOI: 10.1002/jnr.24950] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 06/03/2021] [Accepted: 08/07/2021] [Indexed: 12/16/2022]
Abstract
The brain undergoes rapid, dramatic, and reversible transitioning between states of wakefulness and unconsciousness during natural sleep and in pathological conditions such as hypoxia, hypotension, and concussion. Transitioning can also be induced pharmacologically using general anesthetic agents. The effect is selective. Mobility, sensory perception, memory formation, and awareness are lost while numerous housekeeping functions persist. How is selective transitioning accomplished? Classically a handful of brainstem and diencephalic "arousal nuclei" have been implicated in driving brain-state transitions on the grounds that their net activity systematically varies with brain state. Here we used transgenic targeted recombination in active populations mice to label neurons active during wakefulness with one reporter and neurons active during pentobarbital-induced general anesthesia with a second, contrasting reporter. We found 'wake-on' and 'anesthesia-on' neurons in widely distributed regions-of-interest, but rarely encountered neurons labeled with both reporters. Nearly all labeled neurons were either wake-on or anesthesia-on. Thus, anesthesia-on neurons are not unique to the few nuclei discovered to date whose activity appears to increase during anesthesia. Rather neuronal populations selectively active during anesthesia are located throughout the brain where they likely play a causative role in transitioning between wakefulness and anesthesia. The widespread neuronal suppression reported in prior comparisons of the awake and anesthetized brain in animal models and noninvasive imaging in humans reflects only net differences. It misses the ubiquitous presence of neurons whose activity increases during anesthesia. The balance in recruitment of anesthesia-on versus wake-on neuronal populations throughout the brain may be a key driver of regional and global vigilance states. [Correction added on September 22, 2021, after first online publication: Due to a typesetting error, the abstract text was cut off. This has been corrected now.].
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Affiliation(s)
- Shai-Lee Yatziv
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Or Yudco
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Kristina Vaso
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Adi Mizrahi
- Department of Neurobiology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.,The Edmond and Lily Safra Center for Brain Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Marshall Devor
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel.,Center for Research on Pain, Hebrew University of Jerusalem, Jerusalem, Israel
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5
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Yatziv SL, Strumza N, Minert A, Baron M, Devor M. A nodal point for brain-state transitions: the mesopontine tegmental anesthesia area (MPTA) in mice. Exp Brain Res 2021; 239:3255-3266. [PMID: 34459944 DOI: 10.1007/s00221-021-06204-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 08/18/2021] [Indexed: 12/16/2022]
Abstract
The mesopontine tegmental anesthesia area (MPTA) was identified in rats as a singular brainstem locus at which microinjection of minute quantities of GABAergic agents rapidly and reversibly induces loss-of-consciousness and a state of general anesthesia, while lesioning renders animals insensitive to anesthetics at normal systemic doses. Obtaining similar results in mice has been challenging, however, slowing research progress on how anesthetics trigger brain-state transitions. We have identified roadblocks that impeded translation from rat to mouse and tentatively located the MPTA equivalent in this second species. We describe here a series of modifications to the rat protocol that allowed us to document pro-anesthetic changes in mice following localized stereotactic delivery of minute quantities (20 nL) of the GABAA-receptor agonist muscimol into the brainstem mesopontine tegmentum. The optimal locus identified proved to be homologous to the MPTA in rats, and local neuronal populations in rats and mice were similar in size and shape. This outcome should facilitate application of the many innovative gene-based methodologies available primarily in mice to the study of how activity in brainstem MPTA neurons brings about anesthetic loss-of-consciousness and permits pain-free surgery.
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Affiliation(s)
- Shai-Lee Yatziv
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences 3-533, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Noga Strumza
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences 3-533, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Anne Minert
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences 3-533, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Mark Baron
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences 3-533, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel
| | - Marshall Devor
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences 3-533, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel. .,Center for Research on Pain, The Hebrew University of Jerusalem, 9190401, Jerusalem, Israel.
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6
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Moody OA, Zhang ER, Vincent KF, Kato R, Melonakos ED, Nehs CJ, Solt K. The Neural Circuits Underlying General Anesthesia and Sleep. Anesth Analg 2021; 132:1254-1264. [PMID: 33857967 DOI: 10.1213/ane.0000000000005361] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
General anesthesia is characterized by loss of consciousness, amnesia, analgesia, and immobility. Important molecular targets of general anesthetics have been identified, but the neural circuits underlying the discrete end points of general anesthesia remain incompletely understood. General anesthesia and natural sleep share the common feature of reversible unconsciousness, and recent developments in neuroscience have enabled elegant studies that investigate the brain nuclei and neural circuits underlying this important end point. A common approach to measure cortical activity across the brain is electroencephalogram (EEG), which can reflect local neuronal activity as well as connectivity among brain regions. The EEG oscillations observed during general anesthesia depend greatly on the anesthetic agent as well as dosing, and only some resemble those observed during sleep. For example, the EEG oscillations during dexmedetomidine sedation are similar to those of stage 2 nonrapid eye movement (NREM) sleep, but high doses of propofol and ether anesthetics produce burst suppression, a pattern that is never observed during natural sleep. Sleep is primarily driven by withdrawal of subcortical excitation to the cortex, but anesthetics can directly act at both subcortical and cortical targets. While some anesthetics appear to activate specific sleep-active regions to induce unconsciousness, not all sleep-active regions play a significant role in anesthesia. Anesthetics also inhibit cortical neurons, and it is likely that each class of anesthetic drugs produces a distinct combination of subcortical and cortical effects that lead to unconsciousness. Conversely, arousal circuits that promote wakefulness are involved in anesthetic emergence and activating them can induce emergence and accelerate recovery of consciousness. Modern neuroscience techniques that enable the manipulation of specific neural circuits have led to new insights into the neural circuitry underlying general anesthesia and sleep. In the coming years, we will continue to better understand the mechanisms that generate these distinct states of reversible unconsciousness.
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Affiliation(s)
- Olivia A Moody
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts
| | - Edlyn R Zhang
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts
| | - Kathleen F Vincent
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts
| | - Risako Kato
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts
| | - Eric D Melonakos
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Christa J Nehs
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Ken Solt
- From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts.,Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts
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Avigdor T, Minert A, Baron M, Devor M. Paradoxical anesthesia: Sleep-like EEG during anesthesia induced by mesopontine microinjection of GABAergic agents. Exp Neurol 2021; 343:113760. [PMID: 34000248 DOI: 10.1016/j.expneurol.2021.113760] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 04/08/2021] [Accepted: 05/10/2021] [Indexed: 12/20/2022]
Abstract
General anesthetic agents are thought to induce loss-of-consciousness (LOC) and enable pain-free surgery by acting on the endogenous brain circuitry responsible for sleep-wake cycling. In clinical use, the entire CNS is exposed to anesthetic molecules with LOC and amnesia usually attributed to synaptic suppression in the cerebral cortex and immobility and analgesia to agent action in the spinal cord and brainstem. This model of patch-wise suppression has been challenged, however, by the observation that all functional components of anesthesia can be induced by focal delivery of minute quantities of GABAergic agonists to the brainstem mesopontine tegmental anesthesia area (MPTA). We compared spectral features of the cortical electroencephalogram (EEG) in rats during systemic anesthesia and anesthesia induced by MPTA microinjection. Systemic administration of (GABAergic) pentobarbital yielded the sustained, δ-band dominant EEG signature familiar in clinical anesthesia. In contrast, anesthesia induced by MPTA microinjection (pentobarbital or muscimol) featured epochs of δ-band EEG alternating with the wake-like EEG, the pattern typical of natural non-rapid-eye-movement (NREM) and REM sleep. The rats were not sleeping, however, as they remained immobile, atonic and unresponsive to noxious pinch. Recalling the paradoxical wake-like quality the EEG during REM sleep, we refer to this state as "paradoxical anesthesia". GABAergic anesthetics appear to co-opt both cortical and spinal components of the sleep network via dedicated axonal pathways driven by MPTA neurons. Direct drug exposure of cortical and spinal neurons is not necessary, and is probably responsible for off-target side-effects of systemic administration including monotonous δ-band EEG, hypothermia and respiratory depression. SIGNIFICANCE STATEMENT: The concept that GABAergic general anesthetic agents induce loss-of-consciousness by substituting for an endogenous neurotransmitter, thereby co-opting neural circuitry responsible for sleep-wake transitions, has gained considerable traction. However, the electroencephalographic (EEG) signatures of sleep and anesthesia differ fundamentally. We show that when the anesthetic state is generated by focal delivery of GABAergics into the mesopontine tegmental anesthesia area (MPTA) the resulting EEG repeatedly transitions between delta-wave-dominant and wake-like patterns much as in REM-NREM sleep. This suggests that systemic (clinical) anesthetic delivery, which indiscriminately floods the entire cerebrum with powerful inhibitory agents, obscures the sleep-like EEG signature associated with the less adulterated form of anesthesia obtained when the drugs are applied selectively to loci where the effective neurotransmitter substitution actually occurs.
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Affiliation(s)
- Tamir Avigdor
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Anne Minert
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Mark Baron
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Marshall Devor
- Department of Cell and Developmental Biology, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel; Center for Research on Pain, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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8
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Gruenbaum BF. Comparison of anaesthetic- and seizure-induced states of unconsciousness: a narrative review. Br J Anaesth 2021; 126:219-229. [PMID: 32951841 PMCID: PMC7844374 DOI: 10.1016/j.bja.2020.07.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/23/2020] [Accepted: 07/20/2020] [Indexed: 10/23/2022] Open
Abstract
In order to understand general anaesthesia and certain seizures, a fundamental understanding of the neurobiology of unconsciousness is needed. This review article explores similarities in neuronal and network changes during general anaesthesia and seizure-induced unconsciousness. Both seizures and anaesthetics cause disruption in similar anatomical structures that presumably lead to impaired consciousness. Despite differences in behaviour and mechanisms, both of these conditions are associated with disruption of the functionality of subcortical structures that mediate neuronal activity in the frontoparietal cortex. These areas are all likely to be involved in maintaining normal consciousness. An assessment of the similarities in the brain network disruptions with certain seizures and general anaesthesia might provide fresh insights into the mechanisms of the alterations of consciousness seen in these particular unconscious states, allowing for innovative therapies for seizures and the development of anaesthetic approaches targeting specific networks.
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Kim JL, Bulthuis NE, Cameron HA. The Effects of Anesthesia on Adult Hippocampal Neurogenesis. Front Neurosci 2020; 14:588356. [PMID: 33192273 PMCID: PMC7643675 DOI: 10.3389/fnins.2020.588356] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 09/22/2020] [Indexed: 01/17/2023] Open
Abstract
In animal studies, prolonged sedation with general anesthetics has resulted in cognitive impairments that can last for days to weeks after exposure. One mechanism by which anesthesia may impair cognition is by decreasing adult hippocampal neurogenesis. Several studies have seen a reduction in cell survival after anesthesia in rodents with most studies focusing on two particularly vulnerable age windows: the neonatal period and old age. However, the extent to which sedation affects neurogenesis in young adults remains unclear. Adult neurogenesis in the dentate gyrus (DG) was analyzed in male and female rats 24 h after a 4-h period of sedation with isoflurane, propofol, midazolam, or dexmedetomidine. Three different cell populations were quantified: cells that were 1 week or 1 month old, labeled with the permanent birthdate markers EdU or BrdU, respectively, and precursor cells, identified by their expression of the endogenous dividing cell marker proliferating cell nuclear antigen (PCNA) at the time of sacrifice. Midazolam and dexmedetomidine reduced cell proliferation in the adult DG in both sexes but had no effect on postmitotic cells. Propofol reduced the number of relatively mature, 28-day old, neurons specifically in female rats and had no effects on younger cells. Isoflurane had no detectable effects on any of the cell populations examined. These findings show no general effect of sedation on adult-born neurons but demonstrate that certain sedatives do have drug-specific and sex-specific effects. The impacts observed on different cell populations predict that any cognitive effects of these sedatives would likely occur at different times, with propofol producing a rapid but short-lived impairment and midazolam and dexmedetomidine altering cognition after a several week delay. Taken together, these studies lend support to the hypothesis that decreased neurogenesis in the young adult DG may mediate the effects of sedation on cognitive function.
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Affiliation(s)
| | | | - Heather A. Cameron
- Section on Neuroplasticity, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States
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10
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Vertes RP, Linley SB. No cognitive processing in the unconscious,
anesthetic‐like
, state of sleep. J Comp Neurol 2020; 529:524-538. [DOI: 10.1002/cne.24963] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 05/12/2020] [Accepted: 05/25/2020] [Indexed: 12/13/2022]
Affiliation(s)
- Robert P. Vertes
- Center for Complex Systems and Brain Sciences Florida Atlantic University Boca Raton Florida USA
- Department of Psychology Florida Atlantic University Boca Raton Florida USA
| | - Stephanie B. Linley
- Center for Complex Systems and Brain Sciences Florida Atlantic University Boca Raton Florida USA
- Department of Psychology Florida Atlantic University Boca Raton Florida USA
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Yatziv SL, Yudco O, Dickmann S, Devor M. Patterns of neural activity in the mouse brain: Wakefulness vs. General anesthesia. Neurosci Lett 2020; 735:135212. [PMID: 32593772 DOI: 10.1016/j.neulet.2020.135212] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 06/19/2020] [Accepted: 06/24/2020] [Indexed: 12/13/2022]
Abstract
In light of the general shift from rats to mice as the leading rodent model in neuroscience research we used c-Fos expression as a tool to survey brain regions in the mouse in which neural activity differs between the states of wakefulness and pentobarbital-induced general anesthesia. The aim was to complement prior surveys carried out in rats. In addition to a broad qualitative review, 28 specific regions of interest (ROIs) were evaluated quantitatively. Nearly all ROIs in the cerebral cortex showed suppressed activity during anesthesia. Subcortically, however, some ROIs showed suppression, some showed little change, and some showed increased activity. The overall picture was similar to the rat. Special attention was devoted to ROIs significantly activated during anesthesia, as such loci might actively drive the transition to anesthetic unconsciousness rather than responding passively to inhbitory agents distributed globally (the "wet blanket" hypothesis). Twelve such "anesthesia-on" ROIs were identified: the paraventricular hypothalamic nucleus, supraoptic nucleus, tuberomamillary nucleus, lateral habenular nucleus, dentate gyrus, nucleus raphe pallidus, central amygdaloid nucleus, perifornical lateral hypothalamus, ventro-lateral preoptic area, lateral septum, paraventricular thalamic nucleus and zona incerta. The same primary anti-FOS antibody was used in all mice, but two alternative reporter systems were employed: ABC-diaminobenzidine and the currently more popular AlexaFluor488. Fluorescence tagging revealed far fewer FOS-immunoreactive neurons, sounding an alert that the reporter system chosen can have major effects on results obtained.
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Affiliation(s)
- Shai-Lee Yatziv
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Or Yudco
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Shay Dickmann
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Marshall Devor
- Department of Cell and Developmental Biology, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel; Center for Research on Pain, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
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12
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Individual Mesopontine Neurons Implicated in Anesthetic Loss-of-consciousness Employ Separate Ascending Pathways to the Cerebral Cortex. Neuroscience 2020; 432:188-204. [DOI: 10.1016/j.neuroscience.2020.02.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 02/13/2020] [Accepted: 02/17/2020] [Indexed: 01/19/2023]
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13
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Reduced Sensitivity to Anesthetic Agents upon Lesioning the Mesopontine Tegmental Anesthesia Area in Rats Depends on Anesthetic Type. Anesthesiology 2020; 132:535-550. [DOI: 10.1097/aln.0000000000003087] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Abstract
Background
The brainstem mesopontine tegmental anesthesia area is a key node in circuitry responsible for anesthetic induction and maintenance. Microinjecting the γ-aminobutyric acid–mediated (GABAergic) anesthetic pentobarbital in this nucleus rapidly and reversibly induces general anesthesia, whereas lesioning it renders the animal relatively insensitive to pentobarbital administered systemically. This study investigated whether effects of lesioning the mesopontine tegmental anesthesia area generalize to other anesthetic agents.
Methods
Cell-selective lesions were made using ibotenic acid, and rats were later tested for changes in the dose–response relation to etomidate, propofol, alfaxalone/alfadolone, ketamine, and medetomidine delivered intravenously using a programmable infusion pump. Anesthetic induction for each agent was tracked using five behavioral endpoints: loss of righting reflex, criterion for anesthesia (score of 11 or higher), criterion for surgical anesthesia (score of 14 or higher), antinociception (loss of pinch response), and deep surgical anesthesia (score of 16).
Results
As reported previously for pentobarbital, on-target mesopontine tegmental anesthesia area lesions reduced sensitivity to the GABAergic anesthetics etomidate and propofol. The dose to achieve a score of 16 increased to 147 ± 50% of baseline in control animals ± SD (P = 0.0007; 7 lesioned rats and 18 controls) and 136 ± 58% of baseline (P = 0.010; 6 lesioned rats and 21 controls), respectively. In contrast, responsiveness to the neurosteroids alfaxalone and alfadolone remained unchanged compared with baseline (94 ± 24%; P = 0.519; 6 lesioned rats and 18 controls) and with ketamine increased slightly (90 ± 11%; P = 0.039; 6 lesioned rats and 19 controls). The non-GABAergic anesthetic medetomidine did not induce criterion anesthesia even at the maximal dose tested. The dose to reach the maximal anesthesia score actually obtained was unaffected by the lesion (112 ± 8%; P = 0.063; 5 lesioned rats and 18 controls).
Conclusions
Inability to induce anesthesia in lesioned animals using normally effective doses of etomidate, propofol, and pentobarbital suggests that the mesopontine tegmental anesthesia area is the effective target of these, but not necessarily all, GABAergic anesthetics upon systemic administration. Cortical and spinal functions are likely suppressed by recruitment of dedicated ascending and descending pathways rather than by direct, distributed drug action.
Editor’s Perspective
What We Already Know about This Topic
What This Article Tells Us That Is New
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14
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Laryngeal adductor reflex and future projections for brainstem monitoring. Reply to “A method for intraoperative recording of the laryngeal adductor reflex during lower brainstem surgery in children”. Clin Neurophysiol 2018; 129:2499-2500. [DOI: 10.1016/j.clinph.2018.09.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 09/19/2018] [Indexed: 11/20/2022]
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15
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Enhanced wakefulness following lesions of a mesopontine locus essential for the induction of general anesthesia. Behav Brain Res 2018; 341:198-211. [DOI: 10.1016/j.bbr.2017.12.035] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 12/24/2017] [Accepted: 12/27/2017] [Indexed: 12/16/2022]
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Goldenberg AM, Minert A, Fishman Y, Wolf G, Devor M. Mesopontine Neurons Implicated in Anesthetic Loss-of-consciousness have Either Ascending or Descending Axonal Projections, but Not Both. Neuroscience 2018; 369:152-167. [DOI: 10.1016/j.neuroscience.2017.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 11/02/2017] [Accepted: 11/04/2017] [Indexed: 12/16/2022]
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Location of the Mesopontine Neurons Responsible for Maintenance of Anesthetic Loss of Consciousness. J Neurosci 2017; 37:9320-9331. [PMID: 28821646 DOI: 10.1523/jneurosci.0544-17.2017] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Revised: 08/06/2017] [Accepted: 08/09/2017] [Indexed: 12/14/2022] Open
Abstract
The transition from wakefulness to general anesthesia is widely attributed to suppressive actions of anesthetic molecules distributed by the systemic circulation to the cerebral cortex (for amnesia and loss of consciousness) and to the spinal cord (for atonia and antinociception). An alternative hypothesis proposes that anesthetics act on one or more brainstem or diencephalic nuclei, with suppression of cortex and spinal cord mediated by dedicated axonal pathways. Previously, we documented induction of an anesthesia-like state in rats by microinjection of small amounts of GABAA-receptor agonists into an upper brainstem region named the mesopontine tegmental anesthesia area (MPTA). Correspondingly, lesioning this area rendered animals resistant to systemically delivered anesthetics. Here, using rats of both sexes, we applied a modified microinjection method that permitted localization of the anesthetic-sensitive neurons with much improved spatial resolution. Microinjected at the MPTA hotspot identified, exposure of 1900 or fewer neurons to muscimol was sufficient to sustain whole-body general anesthesia; microinjection as little as 0.5 mm off-target did not. The GABAergic anesthetics pentobarbital and propofol were also effective. The GABA-sensitive cell cluster is centered on a tegmental (reticular) field traversed by fibers of the superior cerebellar peduncle. It has no specific nuclear designation and has not previously been implicated in brain-state transitions.SIGNIFICANCE STATEMENT General anesthesia permits pain-free surgery. Furthermore, because anesthetic agents have the unique ability to reversibly switch the brain from wakefulness to a state of unconsciousness, knowing how and where they work is a potential route to unraveling the neural mechanisms that underlie awareness itself. Using a novel method, we have located a small, and apparently one of a kind, cluster of neurons in the mesopontine tegmentum that are capable of effecting brain-state switching when exposed to GABAA-receptor agonists. This action appears to be mediated by a network of dedicated axonal pathways that project directly and/or indirectly to nearby arousal nuclei of the brainstem and to more distant targets in the forebrain and spinal cord.
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Transient loss of consciousness during hypercapnia and hypoxia: Involvement of pathways associated with general anesthesia. Exp Neurol 2016; 284:67-78. [DOI: 10.1016/j.expneurol.2016.07.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 07/19/2016] [Accepted: 07/20/2016] [Indexed: 12/21/2022]
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