The Ionic Mechanisms Regulating Astrocytic Calcium Dynamic

Abstract

The aim of the study was to understand the effect of alterations in local ionic concentrations due to neuronal activity on calcium activity in astrocytes.Materials and Methods. In this study we investigated astrocytic calcium dynamics using confocal microscopy on hippocampal slices from Wistar rats P15-18.Results. Here we demonstrated that activation of metabotropic glutamate receptors on astrocytes led to an increase of the frequency and duration of calcium events. Elevations of the extracellular calcium concentration did not change the frequency and the duration. Elevations of the extracellular potassium concentration increased the frequency and reduced the duration of calcium events.Conclusions. Neuronal activity causing alterations in local ionic concentrations might affect calcium activity in astrocytes, creating a feedback loop, controlling functioning of neuron-glia networks. These data indicate the complex nature of the effects, which modulate the interplay between neurons and astrocytes that cannot be considered only in the context of a receptor signaling.Key words: hippocampus; astrocytes; calcium oscillations; metabotropic glutamate receptors; neuron-glia interaction.For contacts: Yulia V. Dembitskaya, e-mail: dembitskaya@neuro.nnov.ruThe Ionic Mechanisms Regulating Astrocytic Calcium Dynamic Introduction. Astrocytes represent the most widely studied type of glial cells, due to their involvement in a number of crucial functions in the brain. Such as 1) trophic function [1, 2], by releasing trophic factors regulating proliferation of neurons, neurogenesis, synaptogenesis, axons grow; 2) homeostatic function, by maintaining the water balance via special channels -aquaporins, by removal glutamate from synaptic cleft, preventing excitotoxicity and desensitization of receptors and also by buffering potassium that accumulates extracellularly following action potentials in neurons [2,3]; 3) metabolic function, by involvement in blood-brain barrier maintaining, providing energy support of neurons and removal of metabolites [2,4,5]; 4) signaling function, by generation of calcium signals [2,[6][7][8] and release of gliatransmitters, which can modulate synaptic transmission [3]. These calcium signals represent temporally restricted elevations of calcium in cytosol. They can be triggered mainly by activation of metabotropic receptors (mGluRs) on astrocytic membrane [9][10][11][12] and by mobilization from intracellular stores [9,[12][13][14]. Therefore, calcium plays a role of secondary messenger, that can trigger metabolic reactions, such as gene expression, release of neuroactive substances, gliatransmitters, including