Vitamin D Levels Are Not Associated with Hippocampal-Dependent Learning in Young Adult Male C57BL/6J Mice: A Negative Report

It is well established that vitamin D is essential in calcium homeostasis and bone metabolism. Recent evidence has exposed further roles of vitamin D in adult brain function, specifically indicating that low vitamin D levels during adulthood may be related to cognitive impairment. We have recently shown that adult vitamin D (AVD) deficiency disrupts hippocampal-dependent learning and structural brain connectivity in BALB/c mice. The BALB/c mouse strain is more vulnerable to social stress compared with other resilient mouse strains, such as C57BL/6J mice. Therefore, the primary aim of this research was to examine C57BL/6J mice exposed to varying levels of vitamin D (0, 1500 and 15,000 IU/vitamin D3/kg referred to as deficient, control and elevated, respectively) for 10 weeks. The mice were assessed for hippocampal-dependent learning using the active place avoidance (APA) task. Mice were tested for behaviours that could alter performance on the APA task, and hippocampal tissue was analysed for catecholamine and protein expression. Vitamin D status did not affect spatial learning and memory, general behavioural domains, or catecholamine or protein expression in C57BL/6J mice. Overall, these results indicate that, in contrast to BALB/c mice, vitamin D status does not impact on hippocampal-dependent behaviour in young and healthy, adult male C57BL/6J mice