Postnatal development of the intrinsic nervous system in the circumvallatepapilla-vonEbner gland complex

We have studied the postnatal development of the intrinsic nervous system i n the circumvallate papilla-vonEbner gland complex using NADPH-diaphorase c ytochemistry, immunocytochemistry (for nitric oxide synthase-1 and alpha-in ternexin) and electron microscopy. In rats sacrificed in their first day po st partum (1 p.p.), only isolated NADPH-diaphorase positive neurons were vi sible in the organ. At 2 p.p., a small group of neurons was visible at the base of the papillae and positive neurons formed short chains close to the developing glandular tubules. In the following days, the NADPH-diapharase p ositive cells increased in number and nerve fibres were associated to small ganglia located at the base of the papilla or in the gland. After the firs t week of extrauterine life, the intrinsic nervous system was similar to th e intrinsic system of adult animals. An immunocytochemical positivity for n itric oxide synthase-1 appeared at 4 p.p. in neurons located in the gland a nd at 7 p.p. in cells located at the base of the papilla. Immunocytochemica l staining for alpha-internexin showed that at 1 p.p. developing nerve fibr es were present in the connective tissue of the tongue's muscle layer. At 2 -3 p.p., developing nerve fibres were also present at the bases and in the core of the papilla. In the following days, the positivity for alpha-intern exin was reduced and one week after birth was virtually absent. Ultrastruct ural examination revealed that since 1 p.p. isolated neurons can be found a t the base of the papilla. In conclusion, the intrinsic nervous system orig inates from neurons present in the organ at the birth which, in the first d ays, undergo a biochemical and morphological maturation while the nerve fib res rapidly grow. These findings support the hypothesis that the intrinsic nervous system of the circumvallate papilla has a role in the maturation of the vonEbner gland.