title: Brain region-specific gene expression activation required for reconsolidation and extinction of contextual fear memory.
abstract: During fear conditioning, animals learn an association between a previously neutral or conditioned stimulus (CS) and an aversive or unconditioned stimulus (US). Subsequent reexposure to the CS alone triggers two competing processes. Brief reexposure to the CS initiates reconsolidation processes that serve to stabilize or maintain the original CS-US memory. In contrast, more prolonged reexposure to the CS leads to the formation of an inhibitory extinction (CS-no US) memory. Previous studies have established that both reconsolidation and extinction require gene expression. Consistent with this, here we first show that genetic disruption of cAMP-responsive element-binding protein (CREB)-mediated transcription blocks both reconsolidation and long-term extinction of contextual fear memory. We next asked whether reconsolidation and extinction engage CREB-mediated transcription in distinct brain regions. Accordingly, we used immunohistochemical approaches to characterize the activation of the transcription factor CREB [as well as the expression of the CREB-dependent gene Arc (activity-regulated cytoskeleton-associated protein)] after brief versus prolonged reexposure to a previously conditioned context. After brief reexposure, we observed significant activation of CREB-mediated gene expression in the hippocampus and amygdala. In contrast, after the prolonged reexposure, we observed significant activation of CREB-mediated gene expression in the amygdala and prefrontal cortex. Finally, we showed that blocking protein synthesis in either the hippocampus or the amygdala blocked reconsolidation of contextual fear memory, whereas similar blockade in the amygdala and prefrontal cortex prevented the formation of extinction memory. These experiments establish that reactivated contextual fear memories undergo CREB-dependent reconsolidation or extinction in distinct brain regions.
authors.affiliation: Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Nori
authors.initials: N
authors.lastname: Mamiya
authors.forename: Hotaka
authors.initials: H
authors.lastname: Fukushima
authors.forename: Akinobu
authors.initials: A
authors.lastname: Suzuki
authors.forename: Zensai
authors.initials: Z
authors.lastname: Matsuyama
authors.forename: Seiichi
authors.initials: S
authors.lastname: Homma
authors.forename: Paul W
authors.initials: PW
authors.lastname: Frankland
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kida
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001522:Behavior, Animal; D001921:Brain / Q000033:anatomy & histology* / Q000187:drug effects / Q000378:metabolism*; D003214:Conditioning, Classical; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics; D004965:Estrogen Antagonists / Q000494:pharmacology; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D005239:Fear; D046352:Freezing Reaction, Cataleptic / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D004965:Estrogen Antagonists; D011500:Protein Synthesis Inhibitors; D013629:Tamoxifen; C016601:afimoxifene; D000841:Anisomycin