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Junkins MS, Bagriantsev SN, Gracheva EO. Towards understanding the neural origins of hibernation. J Exp Biol 2022; 225:273864. [PMID: 34982152 DOI: 10.1242/jeb.229542] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Hibernators thrive under harsh environmental conditions instead of initiating canonical behavioral and physiological responses to promote survival. Although the physiological changes that occur during hibernation have been comprehensively researched, the role of the nervous system in this process remains relatively underexplored. In this Review, we adopt the perspective that the nervous system plays an active, essential role in facilitating and supporting hibernation. Accumulating evidence strongly suggests that the hypothalamus enters a quiescent state in which powerful drives to thermoregulate, eat and drink are suppressed. Similarly, cardiovascular and pulmonary reflexes originating in the brainstem are altered to permit the profoundly slow heart and breathing rates observed during torpor. The mechanisms underlying these changes to the hypothalamus and brainstem are not currently known, but several neuromodulatory systems have been implicated in the induction and maintenance of hibernation. The intersection of these findings with modern neuroscience approaches, such as optogenetics and in vivo calcium imaging, has opened several exciting avenues for hibernation research.
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Affiliation(s)
- Madeleine S Junkins
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Sviatoslav N Bagriantsev
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
| | - Elena O Gracheva
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.,Department of Neuroscience and Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA
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Storey K, Logan S. Regrowth and neuronal protection are key for mammalian hibernation: roles for metabolic suppression. Neural Regen Res 2020; 15:2027-2028. [PMID: 32394950 PMCID: PMC7716035 DOI: 10.4103/1673-5374.282242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Horowitz JM, Horwitz BA. Extreme Neuroplasticity of Hippocampal CA1 Pyramidal Neurons in Hibernating Mammalian Species. Front Neuroanat 2019; 13:9. [PMID: 30814935 PMCID: PMC6381046 DOI: 10.3389/fnana.2019.00009] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 01/21/2019] [Indexed: 11/13/2022] Open
Abstract
In awake and behaving mammals (with core and brain temperatures at ~37°C), hippocampal neurons have anatomical and physiological properties that support formation of memories. However, studies of hibernating mammalian species suggest that as hippocampal temperature falls to values below ~10°C, CA1 neurons lose their ability to generate long term potentiation (LTP), a basic form of neuroplasticity. That is, the persistent increase in CA3-CA1 synaptic strength following high-frequency stimulation of CA3 fibers (the hallmark of LTP generation at 37°C) is no longer observed at low brain temperatures although the neurons retain their ability to generate action potentials. In this review, we examine the relationship of LTP to recently observed CA1 structural changes in pyramidal neurons during the hibernation cycle, including the reversible formation of hyperphosphorylated tau. While CA1 neurons appear to be stripped of their ability to generate LTP at low temperatures, their ability to still generate action potentials is consistent with the longstanding proposal that they have projections to neural circuits controlling arousal state throughout the hibernation cycle. Recent anatomical studies significantly refine and extend previous studies of cellular plasticity and arousal state and suggest experiments that further delineate the mechanisms underlying the extreme plasticity of these CA1 neurons.
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Affiliation(s)
- John M Horowitz
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
| | - Barbara A Horwitz
- Department of Neurobiology, Physiology and Behavior, University of California, Davis, Davis, CA, United States
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Silvani A, Cerri M, Zoccoli G, Swoap SJ. Is Adenosine Action Common Ground for NREM Sleep, Torpor, and Other Hypometabolic States? Physiology (Bethesda) 2019; 33:182-196. [PMID: 29616880 DOI: 10.1152/physiol.00007.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
This review compares two states that lower energy expenditure: non-rapid eye movement (NREM) sleep and torpor. Knowledge on mechanisms common to these states, and particularly on the role of adenosine in NREM sleep, may ultimately open the possibility of inducing a synthetic torpor-like state in humans for medical applications and long-term space travel. To achieve this goal, it will be important, in perspective, to extend the study to other hypometabolic states, which, unlike torpor, can also be experienced by humans.
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Affiliation(s)
- Alessandro Silvani
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Matteo Cerri
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy.,National Institute of Nuclear Physics (INFN), Section of Bologna, Bologna , Italy
| | - Giovanna Zoccoli
- Department of Biomedical and Neuromotor Sciences, Alma Mater Studiorum, University of Bologna , Bologna , Italy
| | - Steven J Swoap
- Department of Biology, Williams College , Williamstown, Massachusetts
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Oliver SR, Anderson KJ, Hunstiger MM, Andrews MT. Turning down the heat: Down-regulation of sarcolipin in a hibernating mammal. Neurosci Lett 2018; 696:13-19. [PMID: 30528880 DOI: 10.1016/j.neulet.2018.11.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 11/30/2018] [Accepted: 11/30/2018] [Indexed: 02/01/2023]
Abstract
Hibernation in mammals is a whole-body phenotype that involves profound reductions in oxygen consumption, metabolic reactions, core body temperature, neural activity and heart rate. An important aspect of mammalian hibernation is the ability to reverse this state of hypothermic torpor by rewarming and subsequent arousal. Brown adipose tissue (BAT) and skeletal muscle shivering have been characterized as the predominant driving forces for thermogenesis during arousal. Conversely, the thermogenic contribution of these organs needs to be minimized as hibernating mammals enter torpor. Because skeletal muscle accounts for approximately 40% of the dry mass of the typical mammalian body, we aim to broaden the spotlight to include the importance of down-regulating skeletal muscle non-shivering thermogenesis during hibernation to allow for whole-body cooling and long-term maintenance of a depressed core body temperature when the animal is in torpor. This minireview will briefly describe the current understanding of thermoregulation in hibernating mammals and present new preliminary data on the importance of skeletal muscle and the micro-peptide sarcolipin as a major thermogenic target.
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Affiliation(s)
- S Ryan Oliver
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
| | - Kyle J Anderson
- Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, MN 55812, USA.
| | - Moriah M Hunstiger
- Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.
| | - Matthew T Andrews
- Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331, USA.
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Chen CY, Di Lucente J, Lin YC, Lien CC, Rogawski MA, Maezawa I, Jin LW. Defective GABAergic neurotransmission in the nucleus tractus solitarius in Mecp2-null mice, a model of Rett syndrome. Neurobiol Dis 2017; 109:25-32. [PMID: 28927958 DOI: 10.1016/j.nbd.2017.09.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 08/14/2017] [Accepted: 09/14/2017] [Indexed: 01/12/2023] Open
Abstract
Rett syndrome (RTT) is a devastating neurodevelopmental disorder caused by loss-of-function mutations in the X-linked methyl-CpG binding protein 2 (Mecp2) gene. GABAergic dysfunction has been implicated contributing to the respiratory dysfunction, one major clinical feature of RTT. The nucleus tractus solitarius (NTS) is the first central site integrating respiratory sensory information that can change the nature of the reflex output. We hypothesized that deficiency in Mecp2 gene reduces GABAergic neurotransmission in the NTS. Using whole-cell patch-clamp recordings in NTS slices, we measured spontaneous inhibitory postsynaptic currents (sIPSCs), miniature IPSCs (mIPSCs), NTS-evoked IPSCs (eIPSCs), and GABAA receptor (GABAA-R) agonist-induced responses. Compared to those from wild-type mice, NTS neurons from Mecp2-null mice had significantly (p<0.05) reduced sIPSC amplitude, sIPSC frequency, and mIPSC amplitude but not mIPSC frequency. Mecp2-null mice also had decreased eIPSC amplitude with no change in paired-pulse ratio. The data suggest reduced synaptic receptor-mediated phasic GABA transmission in Mecp2-null mice. In contrast, muscimol (GABAA-R agonist, 0.3-100μM) and THIP (selective extrasynaptic GABAA-R agonist, 5μM) induced significantly greater current response in Mecp2-null mice, suggesting increased extrasynaptic receptors. Using qPCR, we found a 2.5 fold increase in the delta subunit of the GABAA-Rs in the NTS in Mecp2-null mice, consistent with increased extrasynaptic receptors. As the NTS was recently found required for respiratory pathology in RTT, our results provide a mechanism for NTS dysfunction which involves shifting the balance of synaptic/extrasynaptic receptors in favor of extrasynaptic site, providing a target for boosting GABAergic inhibition in RTT.
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Affiliation(s)
- Chao-Yin Chen
- Department of Pharmacology, University of California Davis, One Shields Avenue, Davis, CA 95616, United States.
| | - Jacopo Di Lucente
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Yen-Chu Lin
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Cheng-Chang Lien
- Institute of Neuroscience, National Yang-Ming University, Taipei 112, Taiwan
| | - Michael A Rogawski
- Department of Neurology, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Izumi Maezawa
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States; M.I.N.D. (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Lee-Way Jin
- Department of Pathology and Laboratory Medicine, University of California Davis, One Shields Avenue, Davis, CA 95616, United States; M.I.N.D. (Medical Investigation of Neurodevelopmental Disorders) Institute, University of California Davis, One Shields Avenue, Davis, CA 95616, United States.
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Syrian hamster neuroplasticity mechanisms fail as temperature declines to 15 °C, but histaminergic neuromodulation persists. J Comp Physiol B 2017; 187:779-791. [PMID: 28391591 DOI: 10.1007/s00360-017-1078-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Revised: 12/27/2016] [Accepted: 02/26/2017] [Indexed: 10/19/2022]
Abstract
Previous research suggests that hippocampal neurons in mammalian hibernators shift their major function from memory formation at euthermic brain temperatures (T b = ~37 °C) to modulation of hibernation bout duration as T b decreases. This role of hippocampal neurons during torpor is based in part on in vivo studies showing that histamine (HA) infused into ground squirrel hippocampi lengthened torpor bouts by ~50%. However, it was unclear if HA acted directly on hippocampal neurons or on downstream brain regions via HA spillover into lateral ventricles. To clarify this, we used hippocampal slices to determine if HA would modulate pyramidal neurons at low levels of synaptic activity (as occurs in torpor). We tested the hypotheses that although LTP (a neuroplasticity mechanism) could not be generated at low temperatures, HA (via H2 receptors) would increase population spike amplitudes (PSAs) of Syrian hamster CA1 pyramidal neurons at low stimulation voltages and low temperatures. PSAs were recorded following Schaffer collateral stimulation from subthreshold levels to a maximum response plateau. We found that tetanus evoked LTP at 35 °C but not 15 °C; and at temperatures from 30 to 15 °C, HA significantly enhanced PSA at near threshold levels in slices from non-hibernating hamsters housed in "summer-like" or "winter-like" conditions and from hibernating hamsters. Cimetidine (H2 antagonist) blocked HA-mediated PSA increases in 8 of 8 slices; pyrilamine (H1 antagonist) had no effect in 7 of 8 slices. These results support our hypotheses and show that HA can directly enhance pyramidal neuron excitability via H2 receptors and thus may prolong torpor bouts.
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