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A Functional, Anatomical, and Molecular Investigation of Natural Reward: Sexual Plasticity and Limbic System

Davis, Jon Franklin
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123831570

Abstract Details

2005, PhD, University of Cincinnati, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary.
Reward and reward-based learning are regulated by the limbic system. Repeated exposure to rewarding stimuli has been shown to lead to addictive behavior, and this conversion is hypothesized to be a dependent on learned cues. In this thesis, reward-based learning was tested using male sexual behavior as a model system. Male sexual behavior is a type of natural rewarding behavior that activates various structures within the limbic system. Gaining sexual experience in the rodent is associated with responding to female associated cues leading to increased anticipation of the female and more efficient copulatory behavior. In particular, sex behavior – as well as sex related environmental cues – have been shown to increase neural activation of limbic structures including the nucleus accumbens (Nacc), ventral tegmental area (VTA), and medial prefrontal cortex (mPFC). In an initial set of experiments, the role of the mPFC was examined for an ability to regulate the acquisition and expression of male sexual behavior. In a separate experiment, the role of the mPFC for conditioned aversion to sex behavior was tested. Lesions of the mPFC did not alter the acquisition or expression of male sexual behavior. However, lesions did affect the ability to abstain from sex behavior once it had been paired with aversion. These data suggest that the mPFC is not necessary for the execution of male sexual behavior, but is necessary for behavioral inhibition. In a second set of studies, three separate experiments were conducted to better understand how naturally rewarding behaviors impact limbic system function. To do this, the effects of repeated sex behavior on the function, morphology, and molecular regulation of the mesocorticolimbic system were investigated in a separate set of experiments. Thus, in addition to investigating the role of the mPFC for the acquisition and expression of the behavior, how sex behavior affects the morphology, function, and transcriptional profile of structures within the limbic system was examined. Using a cross sensitization paradigm in which repeated sex exposure was hypothesised to lead to increased locomotor response to amphetamine, one functional study revealed that sex behavior led to an enhanced locomotor response to amphetamine compared to naïve control animals. In addition, sex behavior produced increases in dendritic length and complexity in three different brain regions within the limbic system. In particular sex led to increases in dendritic complexity and length in the Nacc and mPFC, while decreasing the same parameters in VTA neurons. Lastly, sexual behavior led to increases in the expression of genes associated with synaptic plasticity and neuronal excitability within limbic brain regions. In summary, the acquisition or expression of male sexual behavior in the rodent is not dependent on cortical (mPFC) function. However, the ability of male rodents to abstain from sex behavior once they have become aversive is dependent on cortical (mPFC) function. In addition, sex behavior leads to morphological, functional, and molecular changes in limbic structures. Overall these findings suggest that natural reward impacts the limbic system in ways similar to those hypothesized to contribute to addictive behavior.
Dr. Lique Coolen (Advisor)
177 p.
Biology, Neuroscience
limbic; reward; plasticity

Recommended Citations

Citations

  • Davis, J. F. (2005). A Functional, Anatomical, and Molecular Investigation of Natural Reward: Sexual Plasticity and Limbic System [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123831570

    APA Style (7th edition)

  • Davis, Jon. A Functional, Anatomical, and Molecular Investigation of Natural Reward: Sexual Plasticity and Limbic System. 2005. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123831570.

    MLA Style (8th edition)

  • Davis, Jon. "A Functional, Anatomical, and Molecular Investigation of Natural Reward: Sexual Plasticity and Limbic System." Doctoral dissertation, University of Cincinnati, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1123831570

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.