Amygdala Reward Neurons Form and Store Fear Extinction Memory

SummaryThe ability to extinguish conditioned fear memory is critical for adaptive control of fear response, and its impairment is a hallmark of emotional disorders like post-traumatic stress disorder (PTSD). Fear extinction is thought to take place when animals form a new memory that suppresses the original fear memory. However, little is known about the nature and the site of formation and storage of the new extinction memory. Here, we demonstrate that a fear extinction memory engram is formed and stored in a genetically distinct basolateral amygdala (BLA) neuronal population that drive reward behaviors and antagonize the BLA’s original fear neurons. The activation of the fear extinction engram neurons and natural reward-responsive neurons overlap extensively in the BLA. Furthermore, these two neuron subsets are mutually interchangeable in driving reward behaviors and fear extinction behaviors. Thus, fear extinction memory is a newly formed reward memory.

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Environmental enrichment prevents the late effect of acute stress-induced fear extinction deficit: the role of hippocampal AMPA-GluA1 phosphorylation

Translational Psychiatry ◽

10.1038/s41398-020-01140-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Leonardo Santana Novaes ◽

Letícia Morais Bueno-de-Camargo ◽

Carolina Demarchi Munhoz

Keyword(s):

Environmental Enrichment ◽

Basolateral Amygdala ◽

Acute Stress ◽

Fear Memory ◽

Fear Extinction ◽

Post Traumatic Stress ◽

Related Disorder ◽

Memory Extinction ◽

Post Traumatic

AbstractThe persistence of anxiety and the deficit of fear memory extinction are both phenomena related to the symptoms of a trauma-related disorder, such as post-traumatic stress disorder (PTSD). Recently we have shown that single acute restraint stress (2 h) in rats induces a late anxiety-related behavior (observed ten days after stress), whereas, in the present work, we found that the same stress impaired fear extinction in animals conditioned ten days after stress. Fourteen days of environmental enrichment (EE) prevented the deleterious effect of stress on fear memory extinction. Additionally, we observed that EE prevented the stress-induced increase in AMPA receptor GluA1 subunit phosphorylation in the hippocampus, but not in the basolateral amygdala complex and the frontal cortex, indicating a potential mechanism by which it exerts its protective effect against the stress-induced behavioral outcome.

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The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents

Journal of Biological Chemistry ◽

10.1074/jbc.ra119.011527 ◽

2020 ◽

Vol 295 (11) ◽

pp. 3614-3634

Author(s):

Yu Xu ◽

Lucas Cantwell ◽

Andrei I. Molosh ◽

Leigh D. Plant ◽

Dimitris Gazgalis ◽

...

Keyword(s):

Small Molecule ◽

Computational Models ◽

Basolateral Amygdala ◽

Therapeutic Potential ◽

Conditioned Fear ◽

High Specificity ◽

Fear Extinction ◽

Post Traumatic Stress ◽

Girk Channels ◽

Signaling Systems

G-protein–gated inwardly-rectifying K+ (GIRK) channels are targets of Gi/o-protein–signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential. Here, we report on a highly-specific, potent, and efficacious activator of brain GIRK1/2 channels. Using a chemical screen and electrophysiological assays, we found that this activator, the bromothiophene-substituted small molecule GAT1508, is specific for brain-expressed GIRK1/2 channels rather than for cardiac GIRK1/4 channels. Computational models predicted a GAT1508-binding site validated by experimental mutagenesis experiments, providing insights into how urea-based compounds engage distant GIRK1 residues required for channel activation. Furthermore, we provide computational and experimental evidence that GAT1508 is an allosteric modulator of channel–phosphatidylinositol 4,5-bisphosphate interactions. Through brain-slice electrophysiology, we show that subthreshold GAT1508 concentrations directly stimulate GIRK currents in the basolateral amygdala (BLA) and potentiate baclofen-induced currents. Of note, GAT1508 effectively extinguished conditioned fear in rodents and lacked cardiac and behavioral side effects, suggesting its potential for use in pharmacotherapy for post-traumatic stress disorder. In summary, our findings indicate that the small molecule GAT1508 has high specificity for brain GIRK1/2 channel subunits, directly or allosterically activates GIRK1/2 channels in the BLA, and facilitates fear extinction in a rodent model.

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MPP2 Interacts With SK2 Rescue The Excitability of Glutamatergic Neurons in The BLA and Facilitate The Extinction of Conditioned Fear in Mice

10.21203/rs.3.rs-1036689/v1 ◽

2021 ◽

Author(s):

Xiao-Han Peng ◽

Pan-Pan Chen ◽

Yang Zhang ◽

Ke Wu ◽

Ningning Ji ◽

...

Keyword(s):

Fear Conditioning ◽

Basolateral Amygdala ◽

Conditioned Fear ◽

Fear Memory ◽

Fear Extinction ◽

Definitive Evidence ◽

Glutamatergic Neurons ◽

Integral Role ◽

Calcium Activated Potassium Channel ◽

Increased Activity

Abstract Posttraumatic stress disorder (PTSD) and other anxiety disorders stem from dysregulated fear memory in which the basolateral amygdala (BLA) plays an integral role. The excitability of glutamatergic neurons in the BLA correlates with fear memory, and the afterhyperpolarization current (IAHP) mediated by small-conductance calcium-activated potassium channel subtype 2 (SK2) dominates the excitability of glutamatergic neurons. However, definitive evidence for the involvement of the SK2 channel in the BLA in fear extinction is lacking. Here, we discovered that fear conditioning decreased the levers of synaptic SK2 channels in the BLA, which were restored following fear extinction. Notably, reduced expression of synaptic SK2 channels in the BLA during fear conditioning was caused by the increased activity of protein kinase A (PKA), while increased levers of synaptic SK2 channels in the BLA during fear extinction were mediated by interactions with membrane palmitoylated protein 2 (MPP2). Collectively, our results revealed that MPP2 interacts with the SK2 channels and rescues the excitability of glutamatergic neurons by increasing the expression of synaptic SK2 channels in the BLA to promote the normalization of fear memory. These findings expand our understanding of the neurobiological mechanism of PTSD and provide a new direction for PTSD treatment.

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SUN-235 Deficient Fear Extinction in PRKAR1A-Defective Mice

Journal of the Endocrine Society ◽

10.1210/jendso/bvaa046.1855 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

Author(s):

Margaret Keil ◽

Enrica Paradiso ◽

Rita S Keil ◽

Maddalena Ugolini ◽

Evan Harris ◽

...

Keyword(s):

Gene Expression ◽

Fear Conditioning ◽

Conditioned Fear ◽

Critical Role ◽

Fear Memory ◽

Brain Regions ◽

Fear Extinction ◽

Carney Complex ◽

Bdnf Gene ◽

Extinction Learning

Abstract Background: The role of the cAMP/PKA signaling in molecular pathways involved in fear memory is well established: PKA is required for fear memory formation and is a constraint for fear extinction. Previously we reported that a Prkar1a heterozygote (HZ) mouse that was developed in our lab to investigate Carney complex (CNC), the disease caused by PRKAR1A mutations, showed brain region-specific increased PKA activity that was associated with anxiety-like behavioral phenotype and threat bias (Keil, 2010, 2013). We hypothesized that Prkar1a+/- (HZ) mice would have deficits in fear extinction behavior. Brain derived neurotrophic factor (BDNF) has a critical role in formation of fear memory and its transcription is regulated by PKA/CREB. A mouse model with down regulation of PKA provides an opportunity for the first time to investigate the effect of altered PKA signaling on fear conditioning and extinction. Method: Fear conditioning, fear extinction learning, and fear extinction recall were tested in adult male HZ and wild-type (WT) mice as follows: fear conditioning training followed 24hr later by extinction training (new context), then 24hr later by extinction recall training. Percentage of time freezing was used to assess conditioned fear response. We measured BDNF gene expression in brain regions after completion of extinction recall training. Results: As expected, fear conditioning (learning) behavior was similar in HZ and WT mice. However, HZ mice showed a significant deficit in the early phase of fear extinction learning compared to WT. There was no difference in extinction recall between genotypes. Alterations in BDNF gene expression in the prefrontal cortex and amygdala was associated with deficit in fear extinction. Conclusion: Mice with a downregulation of Prkar1a gene demonstrate intact fear conditioning but impaired fear extinction learning, consistent with prior studies that report that PKA inhibition is necessary to facilitate extinction learning. Prkar1a+/- mice provide a valuable model to investigate impaired fear extinction to identify mechanisms for therapeutic targets for anxiety and trauma-related disorders.

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Convergent coding of recent and remote fear memory in the basolateral amygdala

10.1101/2021.09.27.462008 ◽

2021 ◽

Author(s):

Jianfeng Liu ◽

Michael S. Totty ◽

Laila Melissari ◽

Stephen Maren

Keyword(s):

Basolateral Amygdala ◽

Conditioned Fear ◽

Fear Memory ◽

Remote Memory ◽

Storage Site ◽

Long Term Storage ◽

Behavioral Design ◽

Within Subjects ◽

Conditioned Freezing ◽

Evoked Activity

Animals must learn to anticipate recently encountered threats as well as dangers experienced long ago. In both rodents and humans, the basolateral amygdala (BLA) is essential for the encoding and retrieval conditioned fear memories. Although the BLA is a putative storage site for aversive memory, recent evidence suggests that these memories undergo time-dependent reorganization and no longer require the BLA after the passage of time. To explore this question, we systematically examined the role for the BLA in recent and remote fear memory using optogenetic, electrophysiological, and calcium imaging methods in male and female Long-Evans rats. Critically, we used a behavioral design that permits within-subjects comparison of recent and remote memory at the same time point. We found that BLA c-Fos expression was similar after the retrieval of recent (1 day) or remote (2 weeks) fear memories. Extracellular recordings in awake, behaving animals revealed that the majority of BLA neurons encoded both recent and remote memories, suggesting substantial overlap in the allocation of temporally distinct events. Fiber photometric recordings of BLA principal neurons also revealed similar patterns of CS-evoked activity to recent and remote CSs. Consistent with these results, continuous or CS-specific optogenetic inhibition of BLA principal neurons impaired conditioned freezing to both recent and remote CSs. Collectively, these data reveal that single BLA neurons encode both recent and remote fear memories. This may underlie the broad generalization of fear memories across both space and time. Ultimately, these results provide robust evidence that the BLA is a long-term storage site for emotional memories.

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Amygdalar CB2 cannabinoid receptor mediates fear extinction deficits promoted by orexin-A/hypocretin-1

10.22541/au.163908388.84110482/v1 ◽

2021 ◽

Author(s):

Marc Ten-Blanco ◽

África Flores ◽

Inmaculada Pereda-Pérez ◽

Fabiana Piscitelli ◽

Cristina Izquierdo-Luengo ◽

...

Keyword(s):

Basolateral Amygdala ◽

Cannabinoid Receptor ◽

Fear Extinction ◽

Post Traumatic Stress ◽

Orexin A ◽

Post Traumatic ◽

Learned Fear ◽

Endogenous Cannabinoid ◽

Endogenous Cannabinoid System

Background and purpose: Anxiety is often characterized by an inability to extinguish learned fear responses. Orexins/hypocretins are involved in the modulation of aversive memories, and dysregulation of this system may contribute to the aetiology of anxiety disorders characterized by pathological fear. The mechanisms by which orexins regulate fear remain unknown. Experimental approach: We investigated the role of the endogenous cannabinoid system in the impaired fear extinction induced by orexin-A (OXA) in male mice. Behavioural pharmacology, neurochemical, molecular and genetic approaches were used. Key results: The selective inhibitor of 2-arachidonoylglycerol (2-AG) biosynthesis O7460 abolished the fear extinction deficits induced by OXA. Accordingly, increased 2-AG levels were observed in the amygdala and hippocampus of mice treated with OXA that do not extinguish fear, suggesting that high levels of this endocannabinoid are related to poor extinction. Impairment of fear extinction induced by OXA was associated with increased expression of CB2 cannabinoid receptor (CB2R) in microglial cells of the basolateral amygdala. Consistently, the intra-amygdala infusion of the CB2R antagonist AM630 completely blocked the impaired extinction promoted by OXA. Microglial and CB2R expression depletion in the amygdala with PLX5622 chow also prevented these extinction deficits. Conclusions and implications: We reveal that overactivation of the orexin system leads to impaired fear extinction through 2-AG and amygdalar CB2R. This novel mechanism may pave the way towards novel potential approaches to treat diseases associated with inappropriate retention of fear, such as post-traumatic stress disorder, panic anxiety and phobias.

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The accumulation of N6-methyl-2’-deoxyadenosine in DNA drives activity-induced gene expression and is required for the extinction of conditioned fear

10.1101/059972 ◽

2016 ◽

Cited By ~ 1

Author(s):

Xiang Li ◽

Qiongyi Zhao ◽

Wei Wei ◽

Quan Lin ◽

Christophe Magnan ◽

...

Keyword(s):

Gene Expression ◽

Cortical Neurons ◽

Conditioned Fear ◽

Fear Extinction ◽

Adult Brain ◽

Extinction Learning ◽

Prefrontal Cortical ◽

Genome Wide ◽

Extinction Memory ◽

The Brain

Here we report that the recently discovered mammalian DNA modification N6-methyl-2’-deoxyadenosine (m6dA) is dynamically regulated in primary cortical neurons, and accumulates along promoters and coding sequences within the genome of activated prefrontal cortical neurons of adult C57/BI6 mice in response to fear extinction learning. The deposition of m6dA is generally associated with increased genome-wide occupancy of the mammalian m6dA methyltransferase, N6amt1, and this correlates with fear extinction learning-induced gene expression. Of particular relevance for fear extinction memory, the accumulation of m6dA is associated with an active chromatin state and the recruitment of transcriptional machinery to the brain-derived neurotrophic factor (Bdnf) P4 promoter, which is required for Bdnf exon IV mRNA expression and for the extinction of conditioned fear. These results expand the scope of DNA modifications in the adult brain and highlight changes in m6dA as a novel neuroepigenetic mechanism associated with activity-induced gene expression and the formation of fear extinction memory.

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A Single Injection of Pregabalin Induces Short- and Long-Term Beneficial Effects on Fear Memory and Anxiety-Like Behavior in Rats with Experimental Type-1 Diabetes Mellitus.

10.21203/rs.3.rs-1053770/v1 ◽

2021 ◽

Author(s):

Alvaro Henrique Bernardo de Lima Silva ◽

Debora Rasec Radulski ◽

Gabriela Pereira ◽

Alexandra Acco ◽

Janaína Menezes Zanoveli

Keyword(s):

Diabetes Mellitus ◽

Type 1 Diabetes ◽

Type 1 Diabetes Mellitus ◽

Single Injection ◽

Fear Memory ◽

Fear Extinction ◽

Short And Long Term ◽

Extinction Memory

Abstract Anxiety Disorders and Posttraumatic Stress Disorders (PTSD) associated with type 1 diabetes mellitus (DM1) are increasingly common comorbidities and the treatment is quite challenging. In that sense, evidence indicates that the anticonvulsant pregabalin is highly effective in treating severe cases of anxiety, as well as PTSD and diabetic neuropathic pain which is also very prevalent in T1DM. Herein, the short- and long-term effects of a single injection of pregabalin on the acquisition of a fear extinction memory and parameters of anxiety in induced-T1DM animals were investigated. For that, we used the contextual fear conditioning (CFC) and elevated plus maze (EPM) paradigms, respectively. A putative antioxidant activity was also evaluated. Our findings demonstrated that induced-T1DM animals presented greater expression of fear memory, difficulty in extinguishing this fear memory, associated with a more pronounced anxiety-like response. Pregabalin was able to induce a short and long-lasting effect by facilitating the acquisition of the fear extinction memory and inducing a later anxiolytic-like effect. Also, the increased lipid peroxidation levels in the hippocampus and prefrontal cortex of induced-T1DM rats were reduced after pregabalin injection, while the decreased levels of reduced glutathione were increased in the hippocampus. Despite the need for more studies to understand the mechanism of action of pregabalin under these conditions, our data demonstrate for the first time that a single injection of pregabalin in a specific time window was able to improve behavioral parameters in addition to inducing neuroprotective effect. Thus, pregabalin has potential worth exploring for the treatment of PTSD and/or Anxiety associated with T1DM.

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