Neonatal chorda tympani transection permanently disrupts fungiform taste bud and papilla structure in the rat

The present report examined the morphology of fungiform papillae in adult r ats that received bilateral chorda tympani transection at 10 days of age. T ongue tissue was examined using surface-structure analysis. Counts were mad e of fungiform papillae with a pore, fungiform papillae with no pore and fu ngiform papillae with a keratinized conical surface; a feature referred to as "filiform-like." Neonatal chorda tympani nul ve transection resulted not only in a loss of taste buds but also in a permanent loss in numbers of fu ngiform papillae. Compared with an average of 152 fungiform papillae in sha m-operated control rats, there was an average of only 54 fungiform papillae after neonatal chorda tympani transection. Nearly 80% of these fungiform p apillae in neonatal chorda tympani transected rats were filiform-like. No f iliform-like papillae were noted in sham-operated rats. These results sugge st that the chorda tympani nerve is necessary during an early postnatal per iod of devolopment to maintain normal fungiform papillae morphology. (C) 20 00 Elsevier Science Inc. All rights reserved.