Investigating the Dynamic Remodeling of the Peripheral Gustatory System

The taste buds of the fungiform papillae are innervated by neurons of the geniculate ganglion. These peripheral axons of these sensory neurons establish synapses with Taste Receptor Cells (TRCs) to relay taste signals from the tongue to the brain. TRCs have a short lifespan and a high turnover rate, but the geniculate neurons are maintained throughout the animal's life. Therefore, the gustatory sensory neurons must break and re-establish contacts with dying and newly formed TRCs continually within the taste bud to maintain taste sensitivity. Capturing the dynamic changes in morphology of these sensory fibers using traditional histological methods is difficult. To examine what is happening to these fibers' hour by hour or day by day, we needed to implement a new method. To solve this problem and visualize the changes in the morphology of gustatory neurons innervating the taste bud, I developed an in-vivo 2-photon imaging technique. My first aim was to develop a methodology for 2-photon live mouse imaging. With this new method, I could find the same taste fungiform taste bud over multiple days and analyze the morphology and volume of fluorescently labeled gustatory fibers innervating these taste buds (Aim 2). My last aim was to observe the changes in fiber innervation when the mouse was treated with cyclophosphamide, a chemotherapy agent that disrupts the TRCs within the tastevbud. Together, I was able to successfully find and analyze the same taste bud over multiple days with my new methodology. I also found gustatory innervation to change rapidly daily.