Synaptosome Bioenergetics and Calcium Handling: Aging Response

Abstract

Synaptic function and the role of mitochondria inside nerve terminals can be studied by the isolation of an enriched fraction of synaptosomes, which consist in nerve ending particles that are formed during homogenization of brain tissue. Different procedures have been described for the isolation of an enriched fraction of synaptosomes, most of them based on the use of gradients. Neuronal function seems to be critically dependent on the energy provided by mitochondrial respiration. The determination of bioenergetic parameters such as mitochondrial membrane potential, respiratory rates, ATP content and mitochondrial Ca2+ uptake in synaptosomal preparations can provide useful information to analyze the contribution of mitochondrial function to the efficiency of neurotransmission.Synaptic nerve terminals are constantly exposed to extensive Ca2+ fluxes. At the presynaptic terminal, the recovery from calcium oscillations critically depends on the proper mitochondrial function to generate ATP and buffer Ca2+ transients together with an efficient endoplasmic reticulum function.The differential characteristics of synaptic and non-synaptic mitochondria in terms of bioenergetics and free radical production, as well as the response to aging are discussed.