Innervation patterns of individual taste buds during development

To determine whether patterns of taste bud innervation change during postnatal rat development, the number of geniculate ganglion cells that innervate single gustatory papillae were quantified for the tip- and mid-regions of the tongue in adult and developing rats. The number of labeled geniculate ganglion cells innervating a taste bud was correlated with the size of the taste bud. Taste buds were smaller on days 10, 20, and 30 than in adulthood. However, by postnatal day 40 (P40) taste buds were the same size as adult taste buds. Accordingly, there is no correlation between taste bud size and number of innervating ganglion cells, in P10, P20, or P30 rats. There is a correlation between taste bud size and the number of innervating ganglion cells in P40 rats. Thus, the relationship between taste bud size and number of innervating ganglion cells develops over a prolonged postnatal period and is established when taste buds reach their adult size.; Further work examined whether neural rearrangement was important for the development of the relationship between taste bud size and innervation. The number of ganglion cells innervating individual papillae on P10 is correlated with taste bud size becomes by P40. Thus, neural rearrangement occurring between P10 to P40 is not responsible for establishing the relationship between taste bud size and the number of innervating ganglion cells during development.; Finally, the effect of an environmental manipulation (i.e., dietary sodium-restriction) on peripheral taste system development was examined. The adult relationship between taste bud size and number of innervating neurons, does not develop in rats restricted of dietary sodium during development. That is due to a substantial decrease in taste bud volume in rats developmentally restricted of sodium. If developmentally sodium-restricted rats are placed on a normal sodium-replete diet in adulthood, taste buds grow to their normal size. In addition, the relationship between taste bud volume and innervation is established in sodium-repleted rats. The current study revealed that peripheral gustatory anatomy is susceptible to dietary sodium-restriction during development. However, the effects of dietary sodium restriction on peripheral gustatory anatomy can recover in adults.