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Al-Smadi S, Padros A, Goss GG, Dickson CT. The translational inhibitor and amnestic agent emetine also suppresses ongoing hippocampal neural activity similarly to other blockers of protein synthesis. Hippocampus 2024. [PMID: 38785391 DOI: 10.1002/hipo.23611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 04/19/2024] [Accepted: 05/07/2024] [Indexed: 05/25/2024]
Abstract
The consolidation of memory is thought to ultimately depend on the synthesis of new proteins, since translational inhibitors such as anisomycin and cycloheximide adversely affect the permanence of long-term memory. However, when applied directly in brain, these agents also profoundly suppress neural activity to an extent that is directly correlated to the degree of protein synthesis inhibition caused. Given that neural activity itself is likely to help mediate consolidation, this finding is a serious criticism of the strict de novo protein hypothesis of memory. Here, we test the neurophysiological effects of another translational inhibitor, emetine. Unilateral intra-hippocampal infusion of emetine suppressed ongoing local field and multiunit activity at ipsilateral sites as compared to the contralateral hippocampus in a fashion that was positively correlated to the degree of protein synthesis inhibition as confirmed by autoradiography. This suppression of activity was also specific to the circumscribed brain region in which protein synthesis inhibition took place. These experiments provide further evidence that ongoing protein synthesis is necessary and fundamental for neural function and suggest that the disruption of memory observed in behavioral experiments using translational inhibitors may be due, in large part, to neural suppression.
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Affiliation(s)
- S Al-Smadi
- Department of Physiology, University of Alberta, Edmonton, Canada
| | - A Padros
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - G G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - C T Dickson
- Department of Physiology, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, Canada
- Department of Psychology, University of Alberta, Edmonton, Canada
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Kinsky NR, Orlin DJ, Ruesch EA, Diba K, Ramirez S. Erasable Hippocampal Neural Signatures Predict Memory Discrimination. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.02.526824. [PMID: 36778486 PMCID: PMC9915633 DOI: 10.1101/2023.02.02.526824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Memories involving the hippocampus can take several days to consolidate, challenging efforts to uncover the neuronal signatures underlying this process. Using calcium imaging in freely moving mice, we tracked the hippocampal dynamics underlying memory formation across a ten-day contextual fear conditioning (CFC) task. We found that cell turnover between the conditioning chamber and a neutral arena even prior to learning predicted the accuracy of subsequent memory recall the next day. Following learning, context-specific place field remapping correlated with memory performance. To causally test whether these hippocampal dynamics support memory consolidation, we induced amnesia in a group of mice by pharmacologically blocking protein synthesis immediately following learning. We found that halting protein synthesis following learning paradoxically accelerated cell turnover and also arrested learning-related remapping, paralleling the absence of remapping observed in untreated mice that exhibited poor memory expression. Finally, coordinated neural activity that emerged following learning was dependent on intact protein synthesis and predicted memory-related freezing behavior. We conclude that context-specific place field remapping and the development of coordinated ensemble activity require protein synthesis and underlie contextual fear memory consolidation.
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Affiliation(s)
- Nathaniel R. Kinsky
- Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Center for Systems Neuroscience, Boston University, Boston, MA 02451, USA
- These authors contributed equally to this work
| | - Daniel J. Orlin
- Center for Systems Neuroscience, Boston University, Boston, MA 02451, USA
- Neuroscience Graduate Program, Oregon Health & Science University, Portland, OR 97239, USA
- These authors contributed equally to this work
| | - Evan A. Ruesch
- Center for Systems Neuroscience, Boston University, Boston, MA 02451, USA
| | - Kamran Diba
- Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Steve Ramirez
- Center for Systems Neuroscience, Boston University, Boston, MA 02451, USA
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Dastidar SG, Nair D. A Ribosomal Perspective on Neuronal Local Protein Synthesis. Front Mol Neurosci 2022; 15:823135. [PMID: 35283723 PMCID: PMC8904363 DOI: 10.3389/fnmol.2022.823135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 01/17/2022] [Indexed: 11/15/2022] Open
Abstract
Continued mRNA translation and protein production are critical for various neuronal functions. In addition to the precise sorting of proteins from cell soma to distant locations, protein synthesis allows a dynamic remodeling of the local proteome in a spatially variable manner. This spatial heterogeneity of protein synthesis is shaped by several factors such as injury, guidance cues, developmental cues, neuromodulators, and synaptic activity. In matured neurons, thousands of synapses are non-uniformly distributed throughout the dendritic arbor. At any given moment, the activity of individual synapses varies over a wide range, giving rise to the variability in protein synthesis. While past studies have primarily focused on the translation factors or the identity of translated mRNAs to explain the source of this variation, the role of ribosomes in this regard continues to remain unclear. Here, we discuss how several stochastic mechanisms modulate ribosomal functions, contributing to the variability in neuronal protein expression. Also, we point out several underexplored factors such as local ion concentration, availability of tRNA or ATP during translation, and molecular composition and organization of a compartment that can influence protein synthesis and its variability in neurons.
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Huff AE, McGraw SD, Winters BD. Muscarinic (M 1 ) cholinergic receptor activation within the dorsal hippocampus promotes destabilization of strongly encoded object location memories. Hippocampus 2021; 32:55-66. [PMID: 34881482 DOI: 10.1002/hipo.23396] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 08/06/2021] [Accepted: 11/28/2021] [Indexed: 11/09/2022]
Abstract
Following the initial consolidation process, memories can become reactivated by exposure to a reminder of the original learning event. This can lead to the memory becoming destabilized and vulnerable to disruption or other forms of modification. The memory must then undergo the protein-synthesis dependent process of reconsolidation in order to be retained. However, older and/or stronger memories resist destabilization, but can become labile when reactivated in the presence of salient novelty. We have implicated the neurotransmitter acetylcholine, acting at M1 muscarinic cholinergic receptors (mAChRs) within perirhinal cortex (PRh), in novelty-induced destabilization of remote object memories. It remains unclear, however, whether mAChRs are involved in destabilization of other forms of memory. We hypothesized that the role of M1 mAChRs previously demonstrated for PRh-dependent object memory would extend to hippocampus-dependent spatial memory. Using the object location (OL) task, which relies on the dorsal hippocampus (dHPC), we showed that (a) reactivation-dependent reconsolidation of OL memories requires protein synthesis within the dHPC; (b) destabilization of relatively weak OL memories depends on M1 mAChR activation within the dHPC; (c) salient novelty during reactivation promotes destabilization of resistant strongly encoded OL memories; (d) novelty-induced destabilization of strong OL memories requires activation of mAChRs within the dHPC; and (e) M1 mAChR activation within the dHPC in the absence of novelty during memory reactivation mimics the effect of novelty, destabilizing strongly encoded OL memories. These results implicate ACh acting at M1 mAChRs in the destabilization of dHPC-dependent spatial memories, demonstrating generalizability of this cholinergic function beyond memory for object identity. These findings therefore enhance our understanding of the dynamics of long-term memory storage and suggest implications for the treatment of human conditions such as Alzheimer's disease and aging, which are characterized by behavioral and mnemonic inflexibility.
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Affiliation(s)
- Andrew E Huff
- Department of Psychology and Collaborative Neuroscience Program, University of Guelph, Guelph, Ontario, Canada
| | - Shelby D McGraw
- Department of Psychology and Collaborative Neuroscience Program, University of Guelph, Guelph, Ontario, Canada
| | - Boyer D Winters
- Department of Psychology and Collaborative Neuroscience Program, University of Guelph, Guelph, Ontario, Canada
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Prado-Alcalá RA, González-Salinas S, Antaramián A, Quirarte GL, Bello-Medina PC, Medina AC. Imbalance in cerebral protein homeostasis: Effects on memory consolidation. Behav Brain Res 2020; 393:112767. [DOI: 10.1016/j.bbr.2020.112767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/15/2020] [Accepted: 06/07/2020] [Indexed: 01/29/2023]
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Raven F, Bolsius YG, Renssen LV, Meijer EL, Zee EA, Meerlo P, Havekes R. Elucidating the role of protein synthesis in hippocampus‐dependent memory consolidation across the day and night. Eur J Neurosci 2020; 54:6972-6981. [PMID: 31965655 PMCID: PMC8596627 DOI: 10.1111/ejn.14684] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 01/08/2020] [Accepted: 01/13/2020] [Indexed: 01/11/2023]
Abstract
It is widely acknowledged that de novo protein synthesis is crucial for the formation and consolidation of long‐term memories. While the basal activity of many signaling cascades that modulate protein synthesis fluctuates in a circadian fashion, it is unclear whether the temporal dynamics of protein synthesis‐dependent memory consolidation vary depending on the time of day. More specifically, it is unclear whether protein synthesis inhibition affects hippocampus‐dependent memory consolidation in rodents differentially across the day (i.e., the inactive phase with an abundance of sleep) and night (i.e., the active phase with little sleep). To address this question, male and female C57Bl6/J mice were trained in a contextual fear conditioning task at the beginning or the end of the light phase. Animals received a single systemic injection with the protein synthesis inhibitor anisomycin or vehicle directly, 4, 8 hr, or 11.5 hr following training, and memory was assessed after 24 hr. Here, we show that protein synthesis inhibition impaired the consolidation of context–fear memories selectively when the protein synthesis inhibitor was administered at the first three time points, irrespective of timing of training. Even though the basal activity of signaling pathways regulating de novo protein synthesis may fluctuate across the 24‐hr cycle, these results suggest that the temporal dynamics of protein synthesis‐dependent memory consolidation are similar for day‐time and night‐time learning.
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Affiliation(s)
- Frank Raven
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Youri G. Bolsius
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Lara V. Renssen
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Elroy L. Meijer
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Eddy A. Zee
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Peter Meerlo
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
| | - Robbert Havekes
- Groningen Institute for Evolutionary Life Sciences (GELIFES) University of Groningen Groningen The Netherlands
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