Kinetics of taste bud development

The chorda tympani nerve, whose cell bodies are contained within the geniculate ganglion, innervates taste buds in the anterior tongue. There is an excellent match between the size of single taste buds and the number of neurons that innervate them in normal adult rats. However, the match does not occur until postnatal day 40 (P40), which is when taste buds reach their mature size (Krimm and Hill, 1998). Taste bud volume increases greatly over the postnatal period to match the number of neurons that provide innervation.; Dynamic taste bud growth during development can largely be accounted for by addition of cytokeratin 19 positive taste receptor cells to the taste bud. Restriction of dietary sodium during early prenatal development throughout life severely retards taste bud growth normally seen during development. Taste buds from developmentally sodium restricted adult rats contain fewer cytokeratin-19 positive taste receptor cells as compared to control taste buds. This study indicates that taste receptor cell survival or production change significantly during normal development and with dietary manipulations.; To better understand how the coordinated development of taste buds to match innervation pattern occurs, subsequent work examined mechanisms of cell addition during development and following dietary sodium restriction. Age-related differences in cell cycle dynamics of taste bud cells begin before the mature size occurs. Changes in taste bud cell production result from cell cycle alteration, obviating a need for cell lifespan adjustments as a function of development.; Taste cell kinetics in the presence of dietary sodium restriction are strikingly modified as compared to those on a sodium replete diet. Unlike normal development, taste bud cell lifespan is lengthened when animals are raised on a low sodium diet. Thus, environmental cues impact maintenance of taste buds in a manner distinct from developmental processes that create the match between taste bud size and innervation number.; These studies have begun to provide a picture of taste bud cell cycle dynamics and have provided fundamental, new information that extend earlier findings about the relationship between taste bud volume and innervation. Furthermore, findings extend our overall knowledge of cellular processes in taste buds and epithelia in general.