Project description:Background: Extinction-based exposure therapy is used in treating anxiety- and trauma-related disorders, however there is the need to improve its limited efficacy in individuals with impaired fear extinction learning and to facilitate the inadequate protection against return-of-fear phenomena. Methods: Spontaneous recovery and fear renewal tests, assessed persistence and context-independence of treatments rescuing deficient fear extinction in 129S1/SvImJ mice. To reveal neurobiological mechanisms supporting long-lasting extinction rescue, whole-genome expression profiling, qRT-PCR, immunohistochemistry and chromatin immunoprecipitation were used. Results: Persistent and context-independent rescue of deficient fear extinction induced by dietary zinc-restriction was associated with enhanced expression of dopamine-related genes, such as genes encoding the dopamine- D1 (Drd1a) and -D2 (Drd2) receptor in the medial prefrontal cortex (mPFC) and amygdala. Moreover, enhanced histone acetylation was observed in the promoter of the extinction-regulated Drd2 gene in the mPFC, revealing a possibly involved gene regulatory mechanism. While enhancing histone acetylation, via administering the HDAC inhibitor MS275, does not induce successful fear reduction during extinction training, it promoted enduring and context-independent rescue of deficient fear extinction consolidation/retrieval once extinction learning was initiated. This was associated with enhanced neuronal histone acetylation in the mPFC and amygdala. Finally, as a proof of principle, mimicking enhanced dopaminergic signaling by L-dopa treatment rescued deficient fear extinction and co-administration of MS-275 rendered this effect enduring and context-independent. Conclusion: Current data reveal that combining dopaminergic and epigenetic mechanisms is a promising strategy to improve exposure-based behavior therapy in extinction-impaired individuals by initiating the formation of an enduring and context-independent fear inhibitory memory.
Project description:Background: Extinction-based exposure therapy is used in treating anxiety- and trauma-related disorders, however there is the need to improve its limited efficacy in individuals with impaired fear extinction learning and to facilitate the inadequate protection against return-of-fear phenomena. Methods: Spontaneous recovery and fear renewal tests, assessed persistence and context-independence of treatments rescuing deficient fear extinction in 129S1/SvImJ mice. To reveal neurobiological mechanisms supporting long-lasting extinction rescue, whole-genome expression profiling, qRT-PCR, immunohistochemistry and chromatin immunoprecipitation were used. Results: Persistent and context-independent rescue of deficient fear extinction induced by dietary zinc-restriction was associated with enhanced expression of dopamine-related genes, such as genes encoding the dopamine- D1 (Drd1a) and -D2 (Drd2) receptor in the medial prefrontal cortex (mPFC) and amygdala. Moreover, enhanced histone acetylation was observed in the promoter of the extinction-regulated Drd2 gene in the mPFC, revealing a possibly involved gene regulatory mechanism. While enhancing histone acetylation, via administering the HDAC inhibitor MS275, does not induce successful fear reduction during extinction training, it promoted enduring and context-independent rescue of deficient fear extinction consolidation/retrieval once extinction learning was initiated. This was associated with enhanced neuronal histone acetylation in the mPFC and amygdala. Finally, as a proof of principle, mimicking enhanced dopaminergic signaling by L-dopa treatment rescued deficient fear extinction and co-administration of MS-275 rendered this effect enduring and context-independent. Conclusion: Current data reveal that combining dopaminergic and epigenetic mechanisms is a promising strategy to improve exposure-based behavior therapy in extinction-impaired individuals by initiating the formation of an enduring and context-independent fear inhibitory memory.
Project description:Fear extinction is an adaptive behavioral process critical for organism’s survival, but deficiency in extinction may lead to PTSD. While the amygdala and its neural circuits are critical for fear extinction, the molecular identity and organizational logic of cell types that lie at the core of these circuits remain unclear. Here we report that mice deficient for amygdala-enriched gastrin-releasing peptide gene (Grp-/-) exhibit enhanced neuronal activity in the basolateral amygdala (BLA) and stronger fear conditioning, as well as deficient extinction in stress-enhanced fear learning (SEFL). rAAV2-retro-based tracing combined with visualization of the GFP knocked in the Grp gene showed that BLA receives several GRPergic conditioned stimulus projections: from the indirect auditory thalamus-to-auditory cortex pathway, medial prefrontal cortex, ventral hippocampus and ventral tegmental area. Transcription of dopamine-related genes was decreased in BLA of Grp-/- mice following SEFL extinction recall, suggesting that the GRP may mediate fear extinction regulation by dopamine.
Project description:Fear conditioning in rats leads to long term memory (LTM) formation. A central neural substrate for LTM is the basolateral amygdala. We sought the expression changes specific to LTM at 6h following anesthesia with isoflurane (a general anesthetic and an effective amnestic agent), following pain (a component of conditioning), and following conditioning in presence and absence of isoflurane. Keywords = anesthesia, amygdala, LTM, Rampil, Isoflurane, fear, memory Keywords: other
Project description:Fear conditioning in rats leads to long term memory (LTM) formation. A central neural substrate for LTM is the basolateral amygdala. We sought the expression changes specific to LTM at 6h following anesthesia with isoflurane (a general anesthetic and an effective amnestic agent), following pain (a component of conditioning), and following conditioning in presence and absence of isoflurane.
Project description:Memory encodes past experiences, thereby enabling future plans. The basolateral amygdala (BLA) is a center of salience networks that underlie emotional experiences and thus plays a key role in long-term fear memory formation. Here we used single-cell transcriptomics to illuminate the cellular and molecular architecture of the role of the basolateral amygdala in long-term memory. We identified transcriptional signatures in subpopulations of neurons and astrocytes that were memory-specific and persisted for weeks. These transcriptional signatures implicate neuropeptide and brain-derived neurotrophic factor (BDNF) signaling, mitogen-activated protein kinase (MAPK) and cAMP response element-binding protein (CREB) activation, ubiquitination pathways, and synaptic connectivity as key components of long-term memory. Strikingly, upon long-term memory formation a neuronal sub-population defined by increased Penk and decreased Tac expression constituted the most prominent component of the BLA’s memory engram.
Project description:Understanding the mechanisms by which long-term memories are formed and stored in the brain represents a central aim of neuroscience. Prevailing theory suggests that long-term memory encoding involves early plasticity within hippocampal circuits, while reorganization of the neocortex is thought to occur weeks to months later to subserve remote memory storage. Here we report that long-term memory encoding can elicit early transcriptional, structural and functional remodeling of the neocortex. Parallel studies using genome-wide RNA-sequencing, ultrastructural imaging, and whole-cell recording in wild-type mice suggest that contextual fear conditioning initiates a transcriptional program in the medial prefrontal cortex (mPFC) that is accompanied by rapid expansion of the synaptic active zone and postsynaptic density, enhanced dendritic spine plasticity, and increased synaptic efficacy. To address the real-time contribution of the mPFC to long-term memory encoding, we performed temporally precise optogenetic inhibition of excitatory mPFC neurons during contextual fear conditioning. Using this approach, we found that real-time inhibition of the mPFC inhibited activation of the entorhinal-hippocampal circuit and impaired the formation of long-term associative memory. These findings suggest that encoding of long-term episodic memory is associated with early remodeling of neocortical circuits, identify the prefrontal cortex as a critical regulator of encoding-induced hippocampal activation and long-term memory formation, and have important implications for understanding memory processing in healthy and diseased brain states. 4 biological replicates per group were analyzed. The material analyzed was medial prefrontal cortex (mPFC; anterior cingulate cortex subregion) from both brain hemispheres, from which total RNA was extracted.
Project description:These data are from the brains (amygdala and hippocampus) of mice originally derived from a cross between C57BL/6J and DBA/2J inbred strains. We used short-term selection to produce outbred mouse lines with differences in contextual fear conditioning, which is a measure of fear learning. We selected for a total of 4 generations. Fear learning differed in the selected lines and this difference was stronger with each successive generation of selection. These mice also showed differences for measures of anxiety-like behavior, but were not different for tests of non-fear motivated learning, suggesting that selection altered alleles that are specifically involved in emotional behaviors. We identified several QTLs for the selection response. We used Affymetrix microarrays to identify differentially expressed genes in the amygdala and hippocampus of mice from the final generation of selection. Amygdala and hippocampus samples were rapidly dissected out of experimentally naïve mice f rom each selected line. Three samples were pooled and hybridized to each array. Experimentally naïve mice were used because the behavior of the mice can be reliably anticipated due to their lineage. Thus, these gene expression differences are not due to the response to human handling, foot shock or fear-inducing conditioned stimuli. We have a second similar study that focuses on a different selected population that was based on C57BL/6J and A/J mice (see GES4034).