The Role of Energy Substrates in Astrocyte Calcium Activity of Rat Hippocampus in Early Postnatal Ontogenesis

Abstract

Lobachevsky State university of Nizhni Novgorod, 23 Prospekt gagarina, Nizhny Novgorod, 603950, Russian FederationThe aim of the investigation was to study the astroglia functional activity in hippocampal slices of the rat at different postnatal development stages by modeling metabolic changes in the brain.Materials and Methods. The study was carried out on hippocampal slices of Wistar rats of three age groups: postnatal days 5-10, 10-20, and more than 20 days of animal postnatal development using a functional calcium imaging method.Results. In early developmental stages, normal astroglial calcium activity was found to require additional energy substrates. Changing the brain metabolic state at low temperature had no significant effect on astrocyte calcium activity in all postnatal periods under study.Conclusion. The study of astrocyte calcium dynamics in different periods of postnatal development can be used as a method to assess functional activity of glial systems when modeling brain metabolic disorders.Key words: astrocyte; calcium responses; specific energy substrates.For contacts: Lebedeva Albina Vladimirovna, e-mail: lebedeva@neuro.nnov.ru Astroglia is the most numerous glial cells performing a number of critical functions in brain. Astrocytes participate in potassium ion buffering, and regulate local blood flow causing vasoconstriction or vasodilatation. Trophic factors expressing in astrocytes have an effect on neuron growth and the formation of new synapses. Astrocytes have great importance in neuron nourishment by supplying them with glucose and other substances that can serve as energy substrate for neurons [1]. They can also be the main glycogen depot in brain [2].Astrocytes are electrically inactive cells, though they have their own signal system presented by the generation of calcium responses, the duration of which can be up to several seconds [3]. Recent studies [4] have shown astrocytes to be of importance in memory formation by lactate delivered to neurons. In active neuronal work, as well in some nervous system pathologies, lactate is synthesized in astrocytes, lactate being the source of energy for neurons. since neuronal activity depends on availability of energy substrates, the process can also be considered as a mechanism used by astrocytes to regulate neuronal functioning [5].lactate and pyruvate are basic energy substrates in a developing brain, as well as in adult brain, if glucose level is low [6]. moreover, ketone bodies [7] have been shown to act as an energy substrate in the brain of The aim of the investigation was to study the effect of brain metabolic changes such as the age of animal postnatal development, temperature conditions, and the presence of specific energy substrates, on functional (calcium) astrocyte activity in rat hippocampus.

Astrocytic Coverage of Dendritic Spines, Dendritic Shafts, and Axonal Boutons in Hippocampal Neuropil

“…This exchange of metabolites, commonly referred to as the “astrocyte-neuron lactate shuttle” (ANLS), is upregulated during sleep deprivation and exhaustive exercise (Magistretti, 2011 ; Matsui et al, 2017 ). In addition to the energy substrate function, lactate released by astrocytes can serve as a signaling molecule/gliotransmitter to excite neurons and to modulate astrocytic Ca 2+ activity (Tang et al, 2014 ; Lebedeva et al, 2015 ; Magistretti and Allaman, 2018 ). Astrocytes release several other gliotransmitters such as D-serine, glycine, glutamate, GABA, ATP, adenosine etc (Zorec et al, 2012 ; Araque et al, 2014 ).…”

The Ionic Mechanisms Regulating Astrocytic Calcium Dynamic

“…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.…”