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

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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Amygdala Reward Neurons Form and Store Fear Extinction Memory

10.1101/615096 ◽

2019 ◽

Cited By ~ 1

Author(s):

Xiangyu Zhang ◽

Joshua Kim ◽

Susumu Tonegawa

Keyword(s):

Emotional Disorders ◽

Basolateral Amygdala ◽

Conditioned Fear ◽

Fear Memory ◽

Fear Extinction ◽

Neuronal Population ◽

Post Traumatic Stress ◽

Extinction Memory ◽

Memory Engram ◽

Reward Behaviors

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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A Biologically Realistic Network Model of Acquisition and Extinction of Conditioned Fear Associations in Lateral Amygdala Neurons

Journal of Neurophysiology ◽

10.1152/jn.90765.2008 ◽

2009 ◽

Vol 101 (3) ◽

pp. 1629-1646 ◽

Cited By ~ 41

Author(s):

Guoshi Li ◽

Satish S. Nair ◽

Gregory J. Quirk

Keyword(s):

Fear Conditioning ◽

Network Model ◽

Basolateral Amygdala ◽

Conditioned Fear ◽

Pyramidal Cells ◽

Model Learning ◽

Lateral Amygdala ◽

Single Structure ◽

Firing Properties

The basolateral amygdala plays an important role in the acquisition and expression of both fear conditioning and fear extinction. To understand how a single structure could encode these “opposite” memories, we developed a biophysical network model of the lateral amygdala (LA) neurons during auditory fear conditioning and extinction. Membrane channel properties were selected to match waveforms and firing properties of pyramidal cells and interneurons in LA, from published in vitro studies. Hebbian plasticity was implemented in excitatory AMPA and inhibitory GABAA receptor-mediated synapses to model learning. The occurrence of synaptic potentiation versus depression was determined by intracellular calcium levels, according to the calcium control hypothesis. The model was able to replicate conditioning- and extinction-induced changes in tone responses of LA neurons in behaving rats. Our main finding is that LA activity during both acquisition and extinction can be controlled by a balance between pyramidal cell and interneuron activations. Extinction training depressed conditioned synapses and also potentiated local interneurons, thereby inhibiting the responses of pyramidal cells to auditory input. Both long-term depression and potentiation of inhibition were required to initiate and maintain extinction. The model provides insights into the sites of plasticity in conditioning and extinction, the mechanism of spontaneous recovery, and the role of amygdala NMDA receptors in extinction learning.

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Fear Memory

Physiological Reviews ◽

10.1152/physrev.00018.2015 ◽

2016 ◽

Vol 96 (2) ◽

pp. 695-750 ◽

Cited By ~ 150

Author(s):

Ivan Izquierdo ◽

Cristiane R. G. Furini ◽

Jociane C. Myskiw

Keyword(s):

Fear Conditioning ◽

Basolateral Amygdala ◽

Inhibitory Avoidance ◽

Long Term Potentiation ◽

Fear Memory ◽

Contextual Fear Conditioning ◽

Fear Learning ◽

Term Potentiation ◽

Mechanisms Of Memory

Fear memory is the best-studied form of memory. It was thoroughly investigated in the past 60 years mostly using two classical conditioning procedures (contextual fear conditioning and fear conditioning to a tone) and one instrumental procedure (one-trial inhibitory avoidance). Fear memory is formed in the hippocampus (contextual conditioning and inhibitory avoidance), in the basolateral amygdala (inhibitory avoidance), and in the lateral amygdala (conditioning to a tone). The circuitry involves, in addition, the pre- and infralimbic ventromedial prefrontal cortex, the central amygdala subnuclei, and the dentate gyrus. Fear learning models, notably inhibitory avoidance, have also been very useful for the analysis of the biochemical mechanisms of memory consolidation as a whole. These studies have capitalized on in vitro observations on long-term potentiation and other kinds of plasticity. The effect of a very large number of drugs on fear learning has been intensively studied, often as a prelude to the investigation of effects on anxiety. The extinction of fear learning involves to an extent a reversal of the flow of information in the mentioned structures and is used in the therapy of posttraumatic stress disorder and fear memories in general.

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Vagus Nerve Stimulation Enhances Extinction of Conditioned Fear in Rats and Modulates Arc Protein, CaMKII, and GluN2B-Containing NMDA Receptors in the Basolateral Amygdala

Neural Plasticity ◽

10.1155/2016/4273280 ◽

2016 ◽

Vol 2016 ◽

pp. 1-11 ◽

Cited By ~ 22

Author(s):

Amanda C. Alvarez-Dieppa ◽

Kimberly Griffin ◽

Sheridan Cavalier ◽

Christa K. McIntyre

Keyword(s):

Synaptic Plasticity ◽

Vagus Nerve ◽

Nmda Receptors ◽

Fear Conditioning ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Basolateral Amygdala ◽

Conditioned Fear ◽

Associated Proteins

Vagus nerve stimulation (VNS) enhances the consolidation of extinction of conditioned fear. High frequency stimulation of the infralimbic cortex (IL) produces long-term potentiation in the basolateral amygdala (BLA) in rats given VNS-paired extinction training, whereas the same stimulation produces long-term depression in sham-treated rats. The present study investigated the state of synaptic plasticity-associated proteins in the BLA that could be responsible for this shift. Male Sprague-Dawley rats were separated into 4 groups: auditory fear conditioning only (fear-conditioned); fear conditioning + 20 extinction trials (extended-extinction); fear conditioning + 4 extinction trials paired with sham stimulation (sham-extinction); fear conditioning + 4 extinction trials paired with VNS (VNS-extinction). Freezing was significantly reduced in extended-extinction and VNS-extinction rats. Western blots were used to quantify expression and phosphorylation state of synaptic plasticity-associated proteins such as Arc, CaMKII, ERK, PKA, and AMPA and NMDA receptors. Results show significant increases in GluN2B expression and phosphorylated CaMKII in BLA samples from VNS- and extended-extinction rats. Arc expression was significantly reduced in VNS-extinction rats compared to all groups. Administration of the GluN2B antagonist ifenprodil immediately after fear extinction training blocked consolidation of extinction learning. Results indicate a role for BLA CaMKII-induced GluN2B expression and reduced Arc protein in VNS-enhanced extinction.

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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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Dopamine and fear memory formation in the human amygdala

Molecular Psychiatry ◽

10.1038/s41380-021-01400-x ◽

2021 ◽

Author(s):

Andreas Frick ◽

Johannes Björkstrand ◽

Mark Lubberink ◽

Allison Eriksson ◽

Mats Fredrikson ◽

...

Keyword(s):

Fear Conditioning ◽

Dopamine Release ◽

Conditioned Fear ◽

Fear Memory ◽

Memory Formation ◽

Fear Learning ◽

Causative Role ◽

Endogenous Dopamine ◽

Positron Emission ◽

Endogenous Dopamine Release

AbstractLearning which environmental cues that predict danger is crucial for survival and accomplished through Pavlovian fear conditioning. In humans and rodents alike, fear conditioning is amygdala-dependent and rests on similar neurocircuitry. Rodent studies have implicated a causative role for dopamine in the amygdala during fear memory formation, but the role of dopamine in aversive learning in humans is unclear. Here, we show dopamine release in the amygdala and striatum during fear learning in humans. Using simultaneous positron emission tomography and functional magnetic resonance imaging, we demonstrate that the amount of dopamine release is linked to strength of conditioned fear responses and linearly coupled to learning-induced activity in the amygdala. Thus, like in rodents, formation of amygdala-dependent fear memories in humans seems to be facilitated by endogenous dopamine release, supporting an evolutionary conserved neurochemical mechanism for aversive memory formation.

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Regular Music Exposure in Juvenile Rats Facilitates Conditioned Fear Extinction and Reduces Anxiety after Foot Shock in Adulthood

BioMed Research International ◽

10.1155/2019/8740674 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10

Author(s):

Si Chen ◽

Tuo Liang ◽

Fiona H. Zhou ◽

Ye Cao ◽

Chao Wang ◽

...

Keyword(s):

Fear Conditioning ◽

Conditioned Fear ◽

Conditioning Session ◽

Fear Extinction ◽

Extinction Training ◽

Anterior Cingulate ◽

Stressful Event ◽

Sprague Dawley ◽

Positive Role ◽

Juvenile Rats

Music exposure is known to play a positive role in learning and memory and can be a complementary treatment for anxiety and fear. However, whether juvenile music exposure affects adult behavior is not known. Two-week-old Sprague-Dawley rats were exposed to music for 2 hours daily or to background noise (controls) for a period of 3 weeks. At 60 days of age, rats were subjected to auditory fear conditioning, fear extinction training, and anxiety-like behavior assessments or to anterior cingulate cortex (ACC) brain-derived neurotrophic factor (BDNF) assays. We found that the music-exposed rats showed significantly less freezing behaviors during fear extinction training and spent more time in the open arm of the elevated plus maze after fear conditioning when compared with the control rats. Moreover, the BDNF levels in the ACC in the music group were significantly higher than those of the controls with the fear conditioning session. This result suggests that music exposure in juvenile rats decreases anxiety-like behaviors, facilitates fear extinction, and increases BDNF levels in the ACC in adulthood after a stressful event.

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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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