Learning and memory: interrelationships between calcium dynamics and energy metabolism
Ca2+ is the main intracellular second messenger; its multivalence gives the cell the ability to coordinate a series of small and/or large-scale, and sometimes ambiguous, physiological processes such as cell death or proliferation. Thus, evolutionarily and due to its importance in intracellular signaling, it caused the emergence of a series of mechanisms and protein machinery to precisely control its quantity and dynamics in cells. Among all cells, neurons present an enormous range of processes mediated by Ca2+, such as: gene transcription, transmission and synaptic plasticity, changes in plasma membrane permeability, etc. There is an enormous protein apparatus to control the influx, release and removal of this ion from the intracellular medium. Furthermore, due to its versatility and universality, it is assumed that this ion is involved in a series of cognitive processes, such as memory and learning, and nevertheless plays a crucial role in the cellular mechanisms that govern these processes. The framework of studies on learning and memory has demonstrated the intricate management of the use of Ca2+ by the nervous system in the mechanisms of synaptic plasticity, intrinsic neuronal properties and energy metabolism alterations that influence the learning and memory process, emphasizing that modulations or failures in the signaling of the Ca2+ signaling cause cognitive changes. Therefore, this work intends to present how the dynamics of Ca2+ homeostasis and its deregulation would be correlated to different cellular mechanisms of learning and memory. Finally, throughout the text, observations and suggestions on a series of problems are made based on the analysis of several studies. One of them proposes a model of energetic coupling that encompasses not only the known astrocyte-neuron relationship (ANLS), but also between cell cytoplasm and synaptic transmission. Thus, evidencing Ca2+ as a central element of the biology of the nervous system, acting as an internal signaling molecule and consequent production of energy to carry out the activities of neurons.