Browsing by Subject "BNST"
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Item Copulation induces Arc expression in sex-relevant brain regions(2015-05) Turner, Jonathan Michael; Dominguez, Juan M.; Hofmann, JohannThe study of copulation has contributed to knowledge of hormonal effects on behavior and natural reward mechanisms in the brain. In male rats, olfactory cues are particularly important for sexual behavior. Several brain areas are key for the processing of sexually-relevant olfactory stimuli, in particular the medial amygdala (MeA), bed nucleus of the stria terminalis (BNST), and the medial preoptic area (mPOA). These areas also play crucial roles in generating copulatory behavior. Sexual experience is another important factor that improves subsequent sexual behavior and renders males more resistant to the detrimental effects of damage to the aforementioned brain areas. In an effort to identify the brain areas in which changes occur as a result of sexual experience, immunohistochemistry was used to visualize the presence of the immediate early gene (IEG) Arc, which is indicative of activity-dependent synaptic plasticity. Sexually naïve and experienced male rats were either placed in the mating arena alone, with an inaccessible estrous female, or with a receptive female with which they could copulate on the test day. Patterns of Arc and c-Fos expression in their brains were then examined. Sexual experience reduced latencies to mount, intromit, and ejaculate, and also increased the frequency of intromissions during copulation. As expected, copulation induced c-Fos expression in the posterior dorsal MeA, posteromedial BNST, and central mPOA regardless of prior experience. Arc expression was induced by copulation much more widely throughout the anterior BNST, posterior BNST, and MeA, as well as in the posterior mPOA, but not in the central mPOA. Surprisingly, Arc induction did not vary based on prior sexual experience, indicating that neural plasticity induced by copulation is important for both sexually naïve and experienced males. Correlations between measures of sexual behavior and IEG induction revealed that increased Arc in the BNST of naïve males was associated with higher mount latencies and numbers of mounts, while increased Arc in the MeA and mPOA of naïve males was associated with higher intromission latencies and numbers of intromissions. This suggests that Arc induction may be particularly important for improving behavior in naïve males that perform poorest.Item Reversible Inactivation of the Bed Nucleus of the Stria Terminalis Blocks Reinstatement But Not Renewal of Extinguished Fear(2014-12-08) Kim, Janice JThe bed nucleus of the stria terminalis (BNST) is thought to be involved in the expression of fear to shock-associated contexts, but not to discrete conditional stimuli (CSs) paired with shock. Because context plays an important role in the extinction and relapse of fear, we sought to examine the contribution of the BNST to two different relapse phenomena: renewal and reinstatement. In the renewal experiment, male Long-Evans rats received 5 tone-shock trials for conditioning in ?context A?; 24 hours later they received 45 tone?alone (extinction) trials in either ?context B? or ?context C?. Ten minutes prior to a retrieval test (5 tone-alone trials), rats were infused with either selective agonist for GABAA receptors, muscimol or vehicle in the BNST. In the reinstatement experiment, rats underwent a similar procedure, but were presented with an unsignaled ?reminder? shock in the extinction context to reinstate fear. As before, we examined the influence of muscimol inactivation of the BNST during a retrieval testing 24-hours after the reinstatement shock. In the reinstatement test, rats with muscimol infusion showed significantly less freezing than did rats with vehicle infusion. In contrast, BNST inactivation did not attenuate the renewal of fear to an extinguished CS outside the extinction context. These data indicate that the BNST is involved in forms of fear relapse that depend on direct associations of the test context with an aversive US.