Role of calcium in brain aging.

1. Calcium is a universal messenger of extracellular signals in a great variety of cells; it regulates several neuronal functions, such as neurotransmitter synthesis and release, neuronal excitability, phosphorylation and so on. Calcium is also involved in long-term processes, like memory. 2. Recent studies demonstrated that brain aging is characterized by alterations in neuronal function due to the changes in calcium homeostasis. This occurs for various reasons, such as changes in calcium channels, decrease of ion binding to specific proteins and changes in the mechanisms involved in its sequestration and extrusion from neuronal cell. 3. Moreover, it has been shown that high levels of glucocorticoids are neurotoxic, because they alter calcium homeostasis on hypothalamic neurons by increasing calcium voltage-dependent flow, especially in aged neurons. 4. New information about the role of calcium in brain aging could derive from the expansion of new imaging techniques, such as positron emission tomography, single photon emission tomography and nuclear magnetic resonance, which allow in vivo quantitative measurements of functional parameters and their comparison with behavioural data.