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Assessment of the Integrative Roles of the Intergeniculate Leaflet in Circadian Timing and Reward Pathways

Guinn, Jessie, Jr.

Abstract Details

2011, PHD, Kent State University, College of Arts and Sciences / Department of Biological Sciences.
The Intergeniculate leaflet regions (IGL), located in the thalamus, has reciprocal, widespread interactions with multiple limbic, hindbrain and forebrain areas implicated in circadian rhythm regulation. First discovered by Hickey and Spear in 1976, it is thought to integrate inputs from these regions into a phase-resetting signal to the suprachiasmatic nucleus (SCN) circadian clock mediated by neuropeptide Y (NPY) release from geniculohypothalamic tract (GHT) terminals. Included in the diversity of inputs to the IGL is a dense serotonergic projection from the dorsal raphe nucleus (DRN) (Meyer-Bernstein and Morin, 1996). Circadian phase-shift eliciting electrical stimulation of the DRN or novel wheel exposure induces 5-HT release in the IGL (Grossman et al., 2004). Also, Blasiak and Lewandowski (2003 & 2004) showed via electrophysiological recordings that 5-HT and GABA are modulatory on IGL neuronal activity. Bilateral injection of 8-OH-DPAT into the IGL causes phase-advances in wheel-running activity (Challet et al., 1998) and systemic 8-OH-DPAT induces Fos expression in IGL cells (Grossman, 2006). Reward stimuli act on a neural network consisting of the mesolimbic dopamine pathway. This pathway includes dopaminergic neurons in the ventral tegmental area (VTA) and reciprocal interaction with the mesopontine system that includes cholinergic neurons of the pedunculopontine tegmentum (PPT) and the laterodorsal tegmentum (LDT). The IGL receives input from this system that registers the reinforcing effects of natural and drug-related reward. Notably, this non-photic input is cholinergic in nature (Horowitz et al., 2004; Vrang et al., 2003). Thus, the IGL serves as a major integrative hub by processing information from numerous sites to regulate circadian clock timing. Despite this information, critical questions remain concerning the neurophysiological nature of signal integration in the IGL, and how this modulates NPY neuronal activity. To address this knowledge gap, the following experiments were undertaken to assess IGL-NPY neurochemical regulation using bilateral microinjections into both IGLs, evaluation of circadian locomotor rhythmicity and sensitive microdialysis-RIA measurements of in vivo NPY release in the SCN. In regards to reward input to the IGL, experiments were done to investigate the regulatory role of the reward network in circadian timekeeping. This was accomplished by novel wheel exposure, immunohistochemistry, acute electrical stimulation of the VTA and PPT, bilateral microinjection into the IGLs and evaluation of circadian locomotor rhythmicity.
J. David Glass, Ph.D. (Advisor)
Eric M. Mintz, Ph.D. (Committee Member)
Sean L. Veney, Ph.D. (Committee Member)
Qin Liu, Ph.D. (Committee Member)
David C. Riccio, Ph.D. (Committee Member)
115 p.

Recommended Citations

Citations

  • Guinn, Jr., J. (2011). Assessment of the Integrative Roles of the Intergeniculate Leaflet in Circadian Timing and Reward Pathways [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1320094118

    APA Style (7th edition)

  • Guinn, Jr., Jessie. Assessment of the Integrative Roles of the Intergeniculate Leaflet in Circadian Timing and Reward Pathways. 2011. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1320094118.

    MLA Style (8th edition)

  • Guinn, Jr., Jessie. "Assessment of the Integrative Roles of the Intergeniculate Leaflet in Circadian Timing and Reward Pathways." Doctoral dissertation, Kent State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1320094118

    Chicago Manual of Style (17th edition)