Combined effects of testosterone and motor, sensory, or gustatory nerve reinnervation on the regeneration of taste buds

Abstract

Taste buds in the rat's vallate papilla degenerate after bilateral glossopharyngeal nerve transection and reappear after unilateral or bilateral nerve regeneration. The present experiment was performed to determine whether they would rcappear after unilateral reinnervation by motor (hypoglossal), sensory (auriculotemporal), or different gustatory (chorda tympani, vagus) nerves. Since testosterone treatment causes taste buds to appear in new locations in the normal papilla, additional groups of reinnervated animals were given this hormone. Adult male rats were studied 3 months after nerve regeneration; the hormonally treated animals received 2.0 mg. testosterone daily for 3 weeks before being examined. Buds were found in the trench walls (normal location) after glossopharyngeal, chorda tympani, or vagal reinnervation. In the testosterone-treated animals, buds were also found in new locations, namely the top of the papilla and adjacent to it. No buds were found after denervation, unilateral or bilateral auriculotemporal reinnervation, or unilateral hypoglossal reinnervation, even after testosterone treatment. The results indicate that taste bud regeneration is dependent on a property of gustatory nerves that is not shared by general sensory or motor nerves. The appearance of buds in new sites demonstrates that under appropriate conditions additional regions of tongue epithelium can form taste buds.