Ultrastructural changes of the lateral vestibular nucleus in acute experimental thiamine deficiency.

Abstract

This report deals with an ultrastructural study of the lateral vestibular nucleus of 12 rats with acute thiamine deficiency (Group A), 6 rats made deficient but subsequently given a thiamine-supplemented diet and sacrificed when asymptomatic (Group B), and 6 normal controls (Group C). In Group A the most striking changes were observed in the presynaptic boutons and consisted of proliferation of granular-surfaced juxtaposed cisterns, proliferation of smooth-surfaced tubulovesicular cisterns resembling SER, and hypertrophy of the boutons. Other alterations were increased density of the axoplasm, an increased number of mitochondria, a decreased number of synaptic vesicles and necrosis of the matrix. The axons displayed similar assemblies of granular as well as smooth-surfaced cisterns. Moreover, they exhibited fusiform swellings with an increased number of mitochondria, densification of the axoplasm and loss of neurofilaments and microtubules. Although Groups B and C occasionally revealed similar changes in the terminal boutons, these were much less frequent. It is believed that the alterations occurring in acute thiamine deficiency primarily affect the presynaptic boutons and axons, and are for the most part, reversible under the proper treatment.