Influence of multiple deficiency of vitamins, calcium, magnesium and iodine on cognitive function in growing rats

Due to the prevalence of multiple deficiency of vitamins and some minerals among the population, as well as the role of micronutrients in maintaining cognitive functions, the aim of the research was to study the effect of combined deficit of vitamins and/or calcium, magnesium and iodine in the diet of growing Wistar male weaning rats on the manifestation of an unconditioned reflex and ability to learn in response to an electric shock. Mice for the experiment were obtained from Stolbovaya nursery, Federal State Budgetary Scientific Institution Scientific Center of Biomedical Technologies of the Federal Medical-Biological Agency (Moscow region, Russia). After a 5-day feeding on a complete semi-synthetic diet, rats with an initial body weight of 51.4 ± 0.5 g were randomly (according to body weight and the results of the “Elevated Plus Maze” test) divided into four groups (10-12 animals in each group). Subsequently, within 23 days, the animals of the control group (I) received a complete semi-synthetic diet, the rats of Group II (- Ca, Mg, I) were fed on the same diet, but with a 50% reduction in the amount of calcium, magnesium and iodine in the mineral mixture, the rats of Group III (- Vit) received a diet containing 100% of minerals with a reduced amount of vitamin mixture up to 20% with the complete elimination of vitamin E from it. The animals of Group IV (- Vit, Ca, Mg, I) were kept on a diet simultaneously deficient in vitamins and mineral substances. The manifestation of the unconditioned reflex was studied in the “Elevated plus maze” test before feeding the animals on experimental diets and on the 21^st day of feeding. The behavior and memory of animals were evaluated in the test “Conditioned reflex of passive avoidance” on the 7^th day of feeding on experimental diets in response to electrocutaneous irritation of paws (current 0.4 mA, not more than 8 sec.) when entering the dark compartment (development of a conditioned reflex), on the 8^th day -a test of training (a memorable trace), and on the 21^st day - an assessment of longterm memory. Pre-anesthetized with ether, the rats were taken out of the experiment by decapitation, and the content of vitamin E (a-tocopherol) was determined by HPLC, vitamins B₂ and B₂ were measured fluorimetrically in the whole lyophilized brain. In this research, we revealed, that throughout the experiment, the general condition of all animals (appearance and fur) and the body weight did not differ. Reducing the content of vitamins in the diet led to a significant decrease (p < 0.001) in the brain content of selectively measured vitamins B₂ and E at the end of the experiment (See Table 1), that indicated the development of micronutrient deficiency in them. Micronutrient deficiencies for 21 days did not affect the degree of anxiety of the growing rats, assessed in the “Elevated Plus Maze” test. However, the rats from the groups deficient in vitamins (group - Vit and group - Vit, Ca, Mg and I) had a higher motor activity than the animals of the control group and the animals fed on a diet deficient in calcium, magnesium and iodine (group - Ca, Mg and I), which significantly less moved through the maze (See Table 2). In this research, we found out that on the 7^th day of the development of micronutrient deficiency in rats the reproduction of the unconditioned reflex (photophobia) worsened (See Fig. 1). In the rats with vitamin deficiency (group - Vit), the time spent in the open compartments increased 3.0 times compared to the control, whereas in the rats with mineral deficiency (group - Ca, Mg and I) and combined deficiency (group - Vit, Ca, Mg and I) it increased 1.85 and 1.95 times, correspondingly (p < 0.05), while no differences were detected when playing a conditioned reflex 24 hours after training (See Fig. 1). In this research, a significant (p < 0.05) decrease in long-term memory have been discovered in the animals fed on a vitamin-deficient diet (group - Vit) and in the rats fed on a diet with simultaneously reduced levels of vitamins, calcium, magnesium and iodine (group - Vit, Ca, Mg and I). On the basis of the latent time of entry into the dark compartment after 24 hours and 2 weeks, we established that the memory deterioration was due to a decrease in the vitamin content in the diet, whereas the deficit of mineral substances did not affect these parameters (See Fig. 2). In this research, we revealed that multivitamin deficiency in rats exerted an amnestic effect and made a major contribution to impaired learning and long-term memory. This findings suggest the importance of adequate provision of the organism with all vitamins and mineral substances to maintain cognitive functions and memory. The paper contains 2 Figures, 2 Tables and 32 References. The Authors declare no conflict of interest.

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