Brain Clocks & Dendritic Spine Morphology

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/xw42n8990

Abstract

Daily cycles in behavior and physiology, called circadian rhythms, have profound effects on health and well-being. Circadian rhythms that emerge from local molecular clocks in the prefrontal cortex regulate learning and memory. My goal in this study was to determine if genetically encoded fluorescent proteins can produce sufficient signal in dendritic arbors and spines to measure and characterize dendritic spines accurately and reliably. I also aimed to link dendritic spine morphology with time-of-day differences in the learning and recall of cued conditioned fear extinction. Neurons were labelled using an intersectional viral strategy, and dendritic segments were imaged using confocal microscopy. Apical dendritic segments and spines were analyzed with Imaris image analysis software. My results show that fluorescent protein signal can indeed be used to measure dendritic spines in select cases. In addition, the data suggest that circadian rhythms in fear extinction behavior may be driven, in part, by time-of-day differences in distal apical dendritic spine density. My work provides evidence that dendritic spine analysis can be accomplished using widely available transgenic techniques and points to one mechanism by which circadian rhythms regulate extinction behavior.

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