most of these effects is because anesthetics reduce gap junctional and ATP,purinergic, signaling both requires for calcium waves

Dear Eliseo, this is the physiological mechanism of action of the anesthetics and it is true that these effects impair calcium waves, but the problem is how do these effects mediate the loss of consciousness? Is it because they block calcium waves of for another reason?

Terrence Sejnowski and colleagues are advancing our knowledge of the role of astrocytes in brain computational processes:

Proc Natl Acad Sci U S A. 2014 Jul 28. pii: 201410893. [Epub ahead of print]

Astrocytes contribute to gamma oscillations and recognition memory.

Lee HS, Ghetti A, Pinto-Duarte A, Wang X, Dziewczapolski G, Galimi F, Huitron-Resendiz S, Piña-Crespo JC, Roberts AJ, Verma IM, Sejnowski TJ, Heinemann SF.

Abstract

Glial cells are an integral part of functional communication in the brain. Here we show that astrocytes contribute to the fast dynamics of neural circuits that underlie normal cognitive behaviors. In particular, we found that the selective expression of tetanus neurotoxin (TeNT) in astrocytes significantly reduced the duration of carbachol-induced gamma oscillations in hippocampal slices. These data prompted us to develop a novel transgenic mouse model, specifically with inducible tetanus toxin expression in astrocytes. In this in vivo model, we found evidence of a marked decrease in electroencephalographic (EEG) power in the gamma frequency range in awake-behaving mice, whereas neuronal synaptic activity remained intact. The reduction in cortical gamma oscillations was accompanied by impaired behavioral performance in the novel object recognition test, whereas other forms of memory, including working memory and fear conditioning, remained unchanged. These results support a key role for gamma oscillations in recognition memory. Both EEG alterations and behavioral deficits in novel object recognition were reversed by suppression of tetanus toxin expression. These data reveal an unexpected role for astrocytes as essential contributors to information processing and cognitive behavior.

PMID: 25071179 [PubMed - as supplied by publisher]

New results on calcium waves:

1) Extracellular Electrophysiological Measurements of Cooperative Signals in Astrocytes Populations

Front Neural Circuits. 2017 Oct 23;11:80. doi: 10.3389/fncir.2017.00080.

eCollection 2017.

Mestre ALG(1)(2), Inácio PMC(1)(2), Elamine Y(1)(2), Asgarifar S(1)(2), Lourenço

AS(3)(4), Cristiano MLS(1)(5), Aguiar P(6)(7), Medeiros MCR(8), Araújo IM(3)(4),

Ventura J(9), Gomes HL(1)(2).

Author information:

(1)Faculdade de Ciências e Tecnologia, Universidade do Algarve, Faro, Portugal.

(2)Instituto de Telecomunicações, Lisboa, Portugal.

(3)Departamento de Ciências Biomédicas e Medicina, Universidade do Algarve, Faro,

Portugal.

(4)Centro de Investigação em Biomedicina, Universidade do Algarve, Faro,

Portugal.

(5)Centro de Ciências do Mar, Universidade do Algarve, Faro, Portugal.

(6)Instituto de Engenharia Biomédica, Universidade do Porto, Porto, Portugal.

(7)Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto,

Portugal.

(8)Departamento de Engenharia Electrotécnica e de Computadores, Instituto de

Telecomunicações, Universidade de Coimbra, Coimbra, Portugal.

(9)Departamento de Física e Astronomia, Instituto de Física dos Materiais da

Universidade do Porto, Instituto de Nanociências e Nanotecnologia, Universidade

do Porto, Porto, Portugal.

Astrocytes are neuroglial cells that exhibit functional electrical properties

sensitive to neuronal activity and capable of modulating neurotransmission. Thus,

electrophysiological recordings of astroglial activity are very attractive to

study the dynamics of glial signaling. This contribution reports on the use of

ultra-sensitive planar electrodes combined with low noise and low frequency

amplifiers that enable the detection of extracellular signals produced by primary

cultures of astrocytes isolated from mouse cerebral cortex. Recorded activity is

characterized by spontaneous bursts comprised of discrete signals with pronounced

changes on the signal rate and amplitude. Weak and sporadic signals become

synchronized and evolve with time to higher amplitude signals with a

quasi-periodic behavior, revealing a cooperative signaling process. The

methodology presented herewith enables the study of ionic fluctuations of

population of cells, complementing the single cells observation by calcium

imaging as well as by patch-clamp techniques.

DOI: 10.3389/fncir.2017.00080

PMCID: PMC5660104

PMID: 29109679

New results on calcium waves:

2) Three-dimensional Ca2+ imaging advances understanding of astrocyte biology.

Science. 2017 May 19;356(6339). pii: eaai8185. doi: 10.1126/science.aai8185.

Bindocci E(1), Savtchouk I(1), Liaudet N(1), Becker D(1), Carriero G(1), Volterra

A(2).

Author information:

(1)Department of Fundamental Neuroscience, University of Lausanne, 1005 Lausanne,

Switzerland.

(2)Department of Fundamental Neuroscience, University of Lausanne, 1005 Lausanne,

Switzerland. [email protected].

Astrocyte communication is typically studied by two-dimensional calcium ion

(Ca2+) imaging, but this method has not yielded conclusive data on the role of

astrocytes in synaptic and vascular function. We developed a three-dimensional

two-photon imaging approach and studied Ca2+ dynamics in entire astrocyte

volumes, including during axon-astrocyte interactions. In both awake mice and

brain slices, we found that Ca2+ activity in an individual astrocyte is scattered

throughout the cell, largely compartmented between regions, preponderantly local

within regions, and heterogeneously distributed regionally and locally. Processes

and endfeet displayed frequent fast activity, whereas the soma was infrequently

active. In awake mice, activity was higher than in brain slices, particularly in

endfeet and processes, and displayed occasional multifocal cellwide events.

Astrocytes responded locally to minimal axonal firing with time-correlated Ca2+

spots.

Copyright © 2017, American Association for the Advancement of Science.

DOI: 10.1126/science.aai8185

PMID: 28522470

The main target of brain electric stimulation for treating depression:

Astrocytes as a target of transcranial direct current stimulation (tDCS) to treat depression

Hiromu Monai and Hajime Hirase

https://doi.org/10.1016/j.neures.2017.08.012

Highlights

•

tDCS has been shown effective in treating depression, though its mechanisms remain elusive.

•

Astrocytic Ca2+ elevation plays an essential role in tDCS-induced synaptic plasticity in mice.

•

Astrocytic Ca2+ signaling mediates long-term mitigation of depression-like behavior in mice.

•

The literature suggests that astrocytes are a potential therapeutic target for depression.

Abstract

Transcranial direct current stimulation (tDCS) has been reported to be effective in treating mood disorders such as major depressive disorder, however, its detailed mechanism of action is not fully understood. Human and animal experiments have demonstrated that tDCS promotes brain plasticity and have suggested that this consequence may underlie its therapeutic benefits. Nonetheless, the specific neurobiological underpinnings of tDCS-induced brain plasticity have only recently begun to be investigated. While brain plasticity occurs in synapses formed by neurons, astrocytes, a major glial cell type, have recently been shown to support synaptic plasticity via intracellular Ca2+ signaling. In this perspective article, we discuss our recent results demonstrating that tDCS induces the activation of astrocytic calcium signaling that constitutes a required component for treating chronic restraint stress-induced depressive mice. We put forward the notion that activation of astrocytic Ca2+ signaling could be used clinically as a potent remedy for depression.