Browsing by Subject "Medial amygdala"
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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 Estrogen and the aging brain of male rats(2016-12) Nutsch, Victoria Lynn; Dominguez, Juan M.; Gore, Andrea C., 1964-; Hofmann, Hans; Cummings, Molly; Gonzales, RuebenGonadal steroid hormones exert an influence on many aspects of neurobiology in men, including memory, learning and sexual dysfunction. Though testosterone is the main circulating gonadal steroid hormone in males, estradiol is also important, and together these hormones play complementary roles. While the specific roles of estrogen have been studied to some extent in young adults, little is known during aging, when sexual behavior can become impaired. I used a rodent model to examine estradiol’s role in sexual behavior and gene expression in 3 regions, selected for their importance in behavioral neuroendocrine functions and high concentrations of estrogen receptors: the medial preoptic area (mPOA), medial amygdala (MeA), and bed nucleus of the stria terminalis (BnST). My studies focused first on how age and sexual experience affects expression and activation of estrogen receptor α (ERα) and androgen receptor (AR) after sexual behavior in aging intact males. Quantification of neurons expressing hormone receptors in the mPOA revealed that neither ERα nor androgen receptor (AR) showed an age-related change in expression in the mPOA. While both ERα and AR were activated after copulation, the age-related changes were specific to ERα in the central mPOA. There were only mild deficits in sexual behavior. Serum estradiol was also elevated in both aged and copulating animals, but estradiol concentrations only correlated with sexual behavior in aged animals. In a second study, I determined how hormone deprivation (castration) and replacement with estradiol caused changes to gene expression in the mPOA, BnST and MeA. Each region had unique patterns of gene expression in response to aging and estradiol treatment. The mPOA only had changes in expression as a result of hormone administration, while the BnST had primarily age-related changes. The MeA had the greatest number of affected genes, mainly interactions between estradiol treatment and aging. These studies emphasize the importance of estradiol in aging males, and the need for continued study on its role in neuroendocrine and sexual function.