Browsing by Subject "Immediate early gene"
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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 Investigating the female mate preference brain : identifying molecular mechanisms underlying variation in mate preference in specific regions of a swordtail (Xiphophorus nigrensis) brain(2011-05) Wong, Ryan Ying; Hofmann, Hans A.; Cummings, Molly E.; Ryan, Michael J.; Crews, David; Zakon, Harold H.Choosing with whom to mate is one of the most important decisions a female makes in her lifetime and inter-individual variation of these preferences can have important evolutionary consequences. In order to get a complete understanding of why and how females choose a mate, we must identify factors that can contribute to variation of female mate choice. Many decades of research sought to understand ultimate mechanisms of female mate choice with proximate mechanisms receiving a lot more attention in recent years. For my thesis, I identify intrinsic and extrinsic factors that correlate with individual variation of female Xiphophorus nigrensis mate preference. I provide evidence that a female’s size (e.g. age and sexual experience) as well as male behavioral displays can predict female mate preference. Using genes associated with female mate preference (neuroserpin, neurologin-3), I identify four brain regions (Dl, Dm, HV, POA) that show significant differences in gene expression between females exhibiting high preference for males relative to females displaying little mate preference. Neuroserpin and neuroligin-3 gene expression within these brain regions are also positively correlated with female mate preference behavior. Two of these brain regions (Dm and Dl) integrate multisensory information and are found in the putative teleost mesolimbic reward circuitry; the other two regions (HV and POA) are involved in sexual behaviors. With the implication of the reward circuitry, I assess whether there are changes in dopamine synthesis (via tyrosine hydroxylase, TH) in dopaminergic brain regions associated with the degree of mate preference. I do not find evidence of rapid changes (within 30 minutes) of TH expression (i.e. dopamine synthesis) in dopaminergic brain regions related to variation in female mate preference. Collectively my results suggest that mate preference behavior in the brain may be coordinated not just through regions associated with sexual response but also through forebrain areas that may integrate primary sensory information, with no associated changes of a proxy for dopamine synthesis in dopaminergic brain regions.