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Query: UMLS:C0162871 (abdominal aortic aneurysm)
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Despite known health risks, nicotine use remains high, especially in populations diagnosed with mental illnesses, including anxiety disorders and Post-Traumatic Stress Disorder (PTSD). Smoking in these populations may relate to the effects of nicotine on emotional memories. The current study examined the effects of nicotine administration on the extinction of conditioned fear memories. C57BL/6J mice were trained with two white noise conditioned stimulus (CS; 30 s, 85 dB)-foot shock (2 s, 0.57 mA) pairings. Extinction sessions consisted of six presentations of the CS (60 s) across multiple days. Mice were either tested in an AAA design, in which all stages occurred in the same context, or in an ABA design to identify if context changes alter extinction. Saline or nicotine was administered 5 min before training and/or extinction. In the AAA design, nicotine administration before training did not alter extinction. Nicotine administered prior to extinction sessions enhanced extinction and nicotine administered before training and extinction decreased extinction. In the ABA design, nicotine administered before extinction enhanced extinction and blocked context renewal of conditioned fear, while nicotine administered during training and extinction did not alter extinction but enhanced the context renewal of conditioned fear. Nicotine has a differential effect on extinction of fear conditioning depending on when it is administered. Administration during extinction enhances extinction whereas administration during training and extinction may strengthen contextual fear memories and interfere with extinction.
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PMID:Nicotine and extinction of fear conditioning. 1993 99

Exposure therapy is widely used to treat anxiety disorders, including posttraumatic stress disorder (PTSD). However, preventing the return of fear is still a major challenge after this behavioral treatment. An increasing number of studies suggest that high-dose glucocorticoid treatment immediately after trauma can alleviate the symptoms of PTSD in humans. Unknown is whether high-dose glucocorticoid treatment following fear conditioning suppresses the return of fear. In the present study, a typical fear renewal paradigm (AAB) was used, in which the fear response to an auditory cue can be restored in a novel context (context B) when both training and extinction occur in the same context (context A). We trained rats for auditory fear conditioning and administered corticosterone (CORT; 5 and 25mg/kg, i.p.) or vehicle with different delays (1 and 24h). Forty-eight hours after drug injection, extinction was conducted with no drug in the training context, followed by a test of tone-induced freezing behavior in the same (AAA) or a shifted (AAB) context. Both immediate and delayed administration of high-dose CORT after fear conditioning reduced fear renewal. To examine the anxiolytic effect of CORT, independent rats were trained for cued or contextual fear conditioning, followed by an injection of CORT (5 and 25mg/kg, i.p.) or vehicle at a 1 or 24h delay. One week later, anxiety-like behavior was assessed in the elevated plus maze (EPM) before and after fear expression. We found that high-dose CORT decreased anxiety-like behavior without changing tone- or context-induced freezing. These findings indicate that a single high-dose CORT administration given after fear conditioning may selectively suppress fear renewal by reducing anxiety-like behavior and not by altering the consolidation, retrieval, or extinction of fear memory.
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PMID:High-dose corticosterone after fear conditioning selectively suppresses fear renewal by reducing anxiety-like response. 2493 36