Exposure to a stressor produces a long lasting enhancement of fear learning in rats

Abstract In contextual fear conditioning, footshock is given in a context, and re-exposure to this context elicits the conditional defensive response of freezing, a reliable behavioral index of conditional fear. Normally, the amount of contextual freezing is directly proportional to the number of shocks an animal receives in the context. However, pre-exposure to a stressor can produce an enhancement in conditional freezing. Pre-exposure to repeated footshock in one context produces an enhancement of conditional freezing to cues associated with a single shock in a second distinct context. This model of stress-enhanced fear learning (SEFL) can be utilized to study how stress affects learning of future aversive events. The experiments in this paper characterize the magnitude and longevity of SEFL. In the first experiment, the number of footshocks given during the pre-exposure session was varied and conditional fear to the single shock was assessed. Pre-exposure to 1 shock did not produce an enhancement in fear learning in the second context, but pre-exposure to 4 or 15 shocks did. The time-course of the enhancement was examined in the next two experiments. These experiments show that SEFL persists for at least 3 months

Induction and Expression of Fear Sensitization Caused by Acute Traumatic Stress.

Fear promotes adaptive responses to threats. However, when the level of fear is not proportional to the level of threat, maladaptive fear-related behaviors characteristic of anxiety disorders result. Post-traumatic stress disorder develops in response to a traumatic event, and patients often show sensitized reactions to mild stressors associated with the trauma. Stress-enhanced fear learning (SEFL) is a rodent model of this sensitized responding, in which exposure to a 15-shock stressor nonassociatively enhances subsequent fear conditioning training with only a single trial. We examined the role of corticosterone (CORT) in SEFL. Administration of the CORT synthesis blocker metyrapone prior to the stressor, but not at time points after, attenuated SEFL. Moreover, CORT co-administered with metyrapone rescued SEFL. However, CORT alone without the stressor was not sufficient to produce SEFL. In these same animals, we then looked for correlates of SEFL in terms of changes in excitatory receptor expression. Western blot analysis of the basolateral amygdala (BLA) revealed an increase in the GluA1 AMPA receptor subunit that correlated with SEFL. Thus, CORT is permissive to trauma-induced changes in BLA function

Long-Term Safety and Efficacy of Durable Polymer Cobalt-Chromium Everolimus-Eluting Stents in Patients at High Bleeding Risk: A Patient-Level Stratified Analysis From Four Postapproval Studies

BACKGROUND Long-term outcomes in patients at high bleeding risk (HBR) undergoing percutaneous coronary intervention with a drug-eluting stent are unclear. Therefore, we aimed to evaluate long-term adverse events in HBR patients undergoing percutaneous coronary intervention with cobalt-chromium everolimus-eluting stent implantation. METHODS We analyzed stratified data from 4 all-comers postapproval registries. Patients with at least 1 of the following criteria were categorized as HBR: age ≥75 years, history of major bleeding (MB), history of stroke, chronic oral anticoagulant use, chronic kidney disease, anemia, or thrombocytopenia. Additionally, in a separate analysis, patients were categorized according to the recently published Academic Research Consortium HBR criteria. The Kaplan-Meier method was used for time-to-event analyses. Coronary thrombotic events (CTE) included myocardial infarction or definite/probable stent thrombosis. MB was defined according to the TIMI (Thrombolysis in Myocardial Infarction) or GUSTO (Global Use of Strategies to Open Occluded Coronary Arteries) scales. Impact of CTE and MB on subsequent risk of mortality was assessed using multivariable Cox regression with MB and CTE included as time-updated covariates. RESULTS Of the total 10 502 patients included, 3507 (33%) were identified as HBR. Compared with non-HBR patients, those at HBR had more comorbidities, higher lesion complexity, and a higher risk of 4-year mortality (Hazard Ratio [HR] 4.38 [95% CI, 3.76-5.11]). Results were qualitatively similar when using Academic Research Consortium criteria to define HBR. Risk of mortality was increased after CTE (HR 5.02 [95% CI, 3.93-6.41]), as well as after MB (HR 4.92 [95% CI, 3.82-6.35]). Of note, this effect was consistent across the spectrum of bleeding risk (P-interaction test 0.97 and 0.06, respectively). CONCLUSIONS Compared with the non-HBR population, HBR patients experienced worse 4-year outcomes after percutaneous coronary intervention with cobalt-chromium everolimus-eluting stent. Both CTE and MB had a significant impact on subsequent risk of mortality irrespective of bleeding risk

Amygdala Transcriptome and Cellular Mechanisms Underlying Stress-Enhanced Fear Learning in a Rat Model of Posttraumatic Stress Disorder

Severe stress or trauma can cause permanent changes in brain circuitry, leading to dysregulation of fear responses and the development of posttraumatic stress disorder (PTSD). To date, little is known about the molecular mechanisms underlying stress-induced long-term plasticity in fear circuits. We addressed this question by using global gene expression profiling in an animal model of PTSD, stress-enhanced fear learning (SEFL). A total of 15 footshocks were used to induce SEFL and the volatile anesthetic isoflurane was used to suppress the behavioral effects of stress. Gene expression in lateral/basolateral amygdala was measured using microarrays at 3 weeks after the exposure to different combinations of shock and isoflurane. Shock produced robust effects on amygdalar transcriptome and isoflurane blocked or reversed many of the stress-induced changes. We used a modular approach to molecular profiles of shock and isoflurane and built a network of regulated genes, functional categories, and cell types that represent a mechanistic foundation of perturbation-induced plasticity in the amygdala. This analysis partitioned perturbation-induced changes in gene expression into neuron- and astrocyte-specific changes, highlighting a previously underappreciated role of astroglia in amygdalar plasticity. Many neuron-enriched genes were highly correlated with astrocyte-enriched genes, suggesting coordinated transcriptional responses to environmental challenges in these cell types. Several individual genes were validated using RT-PCR and behavioral pharmacology. This study is the first to propose specific cellular and molecular mechanisms underlying SEFL, an animal model of PTSD, and to nominate novel molecular and cellular targets with potential for therapeutic intervention in PTSD, including glycine and neuropeptide systems, chromatin remodeling, and gliotransmission

Induction and Expression of Fear Sensitization Caused by Acute Traumatic Stress

Fear promotes adaptive responses to threats. However, when the level of fear is not proportional to the level of threat, maladaptive fear-related behaviors characteristic of anxiety disorders result. Post-traumatic stress disorder develops in response to a traumatic event, and patients often show sensitized reactions to mild stressors associated with the trauma. Stress-enhanced fear learning (SEFL) is a rodent model of this sensitized responding, in which exposure to a 15-shock stressor nonassociatively enhances subsequent fear conditioning training with only a single trial. We examined the role of corticosterone (CORT) in SEFL. Administration of the CORT synthesis blocker metyrapone prior to the stressor, but not at time points after, attenuated SEFL. Moreover, CORT co-administered with metyrapone rescued SEFL. However, CORT alone without the stressor was not sufficient to produce SEFL. In these same animals, we then looked for correlates of SEFL in terms of changes in excitatory receptor expression. Western blot analysis of the basolateral amygdala (BLA) revealed an increase in the GluA1 AMPA receptor subunit that correlated with SEFL. Thus, CORT is permissive to trauma-induced changes in BLA function