Meissner corpuscles in the palatine mucosae of ddY-mice of various ages were studied histochemically and electron microscopically. As the age of the animals advanced, regressive Meissner corpuscles with lessened or depleted activity of non-specific cholinesterase (ChE) increased in number. Immunohistochemistry for Na+/K+-ATPase showed that the complex ramification of axon terminals in Meissner corpuscles attained at maturation gradually changed to a sparse distribution as the animals aged. Only a few putative rudiments of Meissner corpuscles, which were completely devoid of nerve terminals, were encountered. Electron microscopy showed that the regressive Meissner corpuscles contained atrophic axons and lamellae in a disordered arrangement, although the severity of the atrophy differed depending on the degree of the regression. Furthermore, the Meissner corpuscles were found to progressively accumulate fibrous long-spacing fibers having a periodicity of 160nm and unique spherical corpuscles 150-300nm in diameter in their intercellular spaces.
From these results we concluded that: 1) the atrophy of the axon and lamellae proceeds almost simultaneously during the age-related regression of Meissner corpuscles; and 2) not only the atrophy of the axon and the lamellar cell but microenvironmental changes such as the accumulation of intercellular substances is also involved in the regression of these corpuscles.