The effects of beta-bungarotoxin on the morphogenesis of taste papillae and taste buds in the mouse

Although it has been long accepted that innervation by a taste nerve is ess ential for maintenance of taste buds, it is not clear what role, if any, in nervation plays in the morphogenesis of taste papillae and taste bud develo pment. The following study was undertaken to determine what effects lack of sensory innervation have on the development of taste papillae and the form ation of taste buds in the mouse. Timed-pregnant female mice (n = 3) at ges tational day 12 (gd12) were anesthetized and a 1 mu l solution (1 mu g/mu l ) of beta-bungarotoxin (beta-BTX), a neurotoxin that disrupts sensory and m otor neuron development, was injected into the amniotic cavity of two embry os per dam. Two shams were injected with PBS. Fetuses were harvested at gd 18, 1 day before birth, and four beta-BTX-injected embryos, two shams and t wo controls were fixed in buffered paraformaldehyde. Serial sections were e xamined for the presence and morphology of taste papillae and taste buds. N o nerve profiles were observed in beta-BTX-injected tongues. Although circu mvallate papillae were present on beta-BTX tongues, only five fungiform pap illae could be identified. Taste buds were present on a large percentage of fungiform papillae profiles (24%) a nd on circumvallate papillae in sham a nd control fetuses; in contrast, no taste buds were associated with taste p apillae in beta-BTX fetuses. These results implicate a significant role for innervation in taste papillae and taste bud morphogenesis.