Combined administration of MK-801 and cycloheximide produces a delayed potentiation of fear discrimination memory extinction.
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ABSTRACT:
SUBMITTER: Kochli DE
PROVIDER: S-EPMC5912701 | biostudies-literature | 2018 Apr
REPOSITORIES: biostudies-literature
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Combined administration of MK-801 and cycloheximide produces a delayed potentiation of fear discrimination memory extinction.
Kochli Daniel E DE Campbell Tiffany L TL Hollingsworth Ethan W EW Lab Rain S RS Postle Abagail F AF Perry Megan M MM Mordzinski Victoria M VM Quinn Jennifer J JJ
Behavioral neuroscience 20180401 2
Mixed evidence exists regarding the role of N-methyl-D-aspartate (NMDA) receptors in memory reconsolidation. We provide no evidence that NMDA receptors are involved with memory reconsolidation, but instead demonstrate that prereactivation systemic MK-801 injection, combined with postreactivation intrabasolateral amygdala (BLA) cycloheximide infusion, produces a delayed potentiation of extinction learning. These data suggest that an interaction between NMDA antagonism and protein synthesis inhibi ...[more]
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Project description:BackgroundIn auditory fear conditioning, repeated presentation of the tone in the absence of shock leads to extinction of the acquired fear responses. The glutamate N-methyl-D-aspartate receptor (NMDAR) is thought to be involved in the extinction of the conditioned fear responses, but its detailed role in initiating and consolidating or maintaining the fear extinction memory is unclear. Here we investigated this issue by using a NMDAR antagonist, MK-801.Methods/main findingsThe effects of immediate (beginning at 10 min after the conditioning) and delayed (beginning at 24 h after conditioning) extinctions were first compared with the finding that delayed extinction caused a better and long-lasting (still significant on the 20(th) day after extinction) depression on the conditioned fear responses. In a second experiment, MK-801 was intraperitoneally (i.p.) injected at 40 min before, 4 h or 12 h after the delayed extinction, corresponding to critical time points for initiating, consolidating or maintaining the fear extinction memory. i.p. injection of MK-801 at either 40 min before or 4 h after delayed extinction resulted in an impairment of initiating and consolidating fear extinction memory, which caused a long lasting increased freezing score that was still significant on the 7th day after extinction, compared with extinction group. However, MK-801 administered at 12 h after the delayed extinction, when robust consolidation has been occurred and stabilized, did not affect the established extinction memory. Furthermore, the changed freezing behaviors was not due to an alteration in general anxiety levels, since MK-801 treatment had no effect on the percentage of open-arm time or open-arm entries in an Elevated Plus Maze (EPM) task.Conclusions/significanceOur data suggested that the activation of NMDARs plays important role in initiation and consolidation but not maintenance of fear extinction memory. Together with the fact that NMDA receptor is very important for memory, our data added experimental evidence to the concept that the extinction of conditioned fear responses is a procedure of initiating and consolidating new memory other than simply "erasing" the fear memory.
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Project description:Study Objectives:Insomnia increases the risk for anxiety disorders that are also associated with fear-extinction deficits. We compared activation of fear and extinction networks between insomnia disorder (ID) without comorbidity and good sleepers (GS). Methods:Twenty-three ID participants age- and sex-matched to 23 GS participants completed 14 days of actigraphy and diaries, three nights of ambulatory polysomnography and a 2-day fear conditioning and extinction paradigm. Fear conditioning and extinction learning occurred on the first day, followed 24 hours later by extinction recall. Blood-oxygen-level-dependent functional magnetic resonance imaging (fMRI) signal and skin conductance responses (SCR) were recorded. Nineteen participants per group produced usable fMRI data. Beta weights from areas where activation differed between groups were regressed against sleep and psychophysiological measures. SCR was compared between groups at various stages of the paradigm. Results:During fear conditioning, both ID (N = 19) and GS (N = 19) activated fear-related structures. Across extinction learning, ID (N = 19) demonstrated little change, whereas GS (N = 16) activated both fear and extinction-related areas, including the hippocampus, insula, dorsal anterior cingulate (dACC), and ventromedial prefrontal (vmPFC) cortices. During extinction recall, while GS (N = 17) demonstrated limited activation, ID (N = 16) activated regions similar to those previously activated in GS (vmPFC, dACC, insula). Sleep quality was predictive of activations seen at various stages of the paradigm. SCR data suggested ID were more physiologically reactive than GS. Conclusions:Across extinction learning, GS but not ID activated both fear and extinction-related networks. At extinction recall, ID engaged similar regions whereas GS no longer did so. Individuals with ID may show a delayed acquisition of fear extinction memories.
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Project description:MK-801, an N-methyl-D-aspartate antagonist in mammalian brain tissue, is a potent nematocidal agent. Specific MK-801 binding sites have been identified and characterized in a membrane fraction prepared from the free-living nematode Caenorhabditis elegans. The high-affinity MK-801 binding site has an apparent dissociation constant, Kd, of 225 nM. Unlike the MK-801 binding site in mammalian tissues, the C. elegans binding site is not effected by glutamate or glycine, and polyamines are potent inhibitors of specific MK-801 binding.
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Project description:Background: microRNAs (miRNAs) are small, non-coding RNAs, which can silence the expression of various target genes via binding their mRNAs, thus miRNAs serve and regulate a wide range of crucial functions in the body. However, the miRNAs expression profile after the antipsychotics mediation in schizophrenia is largely unknown. Methods: Noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonists like as MK-801 had been shown to provide a useful animal model to investigate these effects of schizophrenia-like symptoms in rodent animals. In this study, the rat hippocampal miRNA expression profiles were examined after the antipsychotic clozapine (CLO) treated the MK-801-pretreated Sprague Dawley rats. The total RNA samples from their hippocampus of three rat groups were sequenced using next generation sequencing (NGS), then processed bioinformatic analysis. Results: Successfully, we identified 8 miRNAs’ expressions were significantly different in the MK-801 group comparing the VEH control group. Interestingly, 14 miRNAs were largely changed expression in CLO+MK-80-treated group comparing the MK-801-pretreated group, in which the rno-miR-184 was up-regulated significantly. Subsequently, further analyses suggested these miRNAs could modulate their target genes involving in the regulation of endocytosis, ubiquitin mediated proteolysis and regulation of actin cytoskeleton, which might be involved in the important mechanism of schizophrenia. Conclusion: Our results suggested the altered miRNA expressions might play an important role in the complex pathophysiology of schizophrenia, and subsequently impacted on brain functions.
2020-10-01 | GSE129466 | GEO