Vitamin A deficiency produces spatial learning and memory impairment in rats

Vitamin A and its derivatives (retinoids) play important roles in many physiological processes. The recent finding of high levels of cellular retinol-binding protein type 1 immunoreactivity, cellular retinoic acid-binding protein type 1 immunoreactivity and the presence of nuclear retinoid receptors in the central nervous system of adult rodents suggests that retinoids may carry out important roles in the adult brain. In consideration of the role of the hippocampus in spatial learning and memory we evaluated the effect of vitamin A deprivation in adult rats on these functions. Following 12 weeks of vitamin A-free diet, rats were trained to acquire a radial-arm maze task. Results show that this diet induced a severe deficit in the spatial learning and memory task. The cognitive impairment was fully restored when vitamin A was replaced in the diet. We also found a significant decrease in hippocampal acetylcholine release induced by scopolamine, assessed using microdialysis technique, and a reduction in the size of hippocampal nuclei of CA1 region in vitamin-deficient rats, compared to rats fed with a vitamin A-sufficient diet. These results demonstrate that vitamin A has a critical role in the learning and memory processes linked to a proper hippocampal functioning.