The effect of vitamin E deficiency on the plasticity of cholinergic synapses: a computer-assisted morphometric study.

A computer-assisted morphometric study has been carried out on the ultrastructural features of the cholinergic synaptic junctional areas in the dentate gyrus supragranular layer of 11-month-old female Wistar rats and in littermates fed a vitamin E deficient diet for 10 months. The number of synapses/micro m(3) (numerical density: Nv), the average area of the junctional zones (S) and the total synaptic contact area/micro m(3) (surface density: Sv) were the three parameters taken into account. Nv and Sv significantly decreased, while S increased in the vitamin E deficient group. A size distribution of S showed that while in the normally fed animals the percentage of an enlarged synapses (0.16 micro m(2)>) accounts for 19% of the whole population, in the vitamin E deficient rats it raises at 44%. Relating the number of synapses to the number of dentate gyrus granule cells, the synapse-to-neurone ratio appeared to be decreased by 30% in the vitamin E deficient animals. It is currently reported that number (Nv) and size (S) of the synapses are in a close inverse relationship which aims at maintaining constant the total synaptic surface area (Sv) in a discrete volume of the neuropil, therefore, taken together per experimental group of rats, these parameters represent a reliable index of the synaptic morphological plasticity. Our present findings clearly document that the structural dynamics of the hippocampal cholinergic synapses are markedly affected by the absence of vitamin E from the diet and, in turn, support that an increased peroxidative stress may play a central role in the widely reported vulnerability of the cholinergic terminals with advancing age.