An Examination of Microglia Presence Following Chorda Tympani Transection Across Rat Development

The chorda tympani (CT) nerve transmits taste information from the tongue to the nucleus of the solitary tract (NTS) in the brainstem. Following transection of the CT (CTX) in adult rats (over 40 days of age), structural and functional changes occur but return to control-like status after approximately 45 days (St. John, Markison, & Spector, 1995). However, if the nerve damage occurs to the rats prior to maturation, similar but more drastic changes occur, with the most severe effects occurring when the damage occurs at 5 or 10 days of age, where the damage is permanent (Sollars, 2005). The mechanisms behind these developmentally-dependent changes are unclear. Microglia cells are a classification of non-neuronal cells in the central nervous system that perform a myriad of functions, one of which is to respond to damage and inflammation (Rock et al., 2004). Microglia are known to be present in the NTS of adult mice four days after CTX (Bartel, 2013). The proposed study will examine the microglial presence in the NTS following CTX at 5, 10, 25, or 40 days of age to see if the response trend is comparable to the observed developmentally-dependent functional and structural effects. It is hypothesized that the microglial presence following injury will be greater in the youngest age group and will be less prominent as the experimental age increases. Data obtained from this study could assist in a better understanding of central nervous system plasticity, protection, and peripheral regeneration following injury