Abstract

In the general deterioration of physiological functions that takes place in aging, the prevalence of cognitive impairments, and particularly of those related to learning and memory, makes these deficits a major concern of public health. Although the exact nature of cellular and molecular substrates underlying learning and memory still remains an open issue for the neurobiologist, the current hypothesis views it is determined by the capacity of brain neuronal networks to express short- and long-term changes in synaptic strength. Accordingly, the capacity of functional plasticity is impaired in the brain of aged memory-deficient animals. Short-term changes in synaptic transmission closely depend on transmitter release and neuronal excitability while long-term modifications are mainly related to the activation of the N-methyl-D-aspartate receptor (NMDA-R), a subtype of glutamate receptors. Because transmitter release, neuronal excitability and NMDA-R activation are modulated by magnesium (Mg2+), a change in brain Mg2+ homeostasis could affect synaptic strength and plasticity in neuronal networks and consequently could alter memory capacities. In addition, alteration of brain Mg2+ levels could be regarded as a possible mechanism contributing to cognitive aging. According to these postulates, long-term increase in Mg2+ levels facilitates the conversion of synapses to a plastic state while learning and memory capacities are enhanced in adult animals fed with a diet enriched in Mg2+-L-threonate, a treatment that significantly elevates brain Mg2+ levels. Because Mg2+-L-threonate also improves learning and memory in aged animals, the regulation of brain Mg2+ homeostasis may therefore be regarded as a relevant target for the development of new pharmacological strategies aimed at minimizing cognitive aging.