The Hippocampal astrocytes may have specific property, which other astrocytes in other brain regions do not have it.
they may be categorized in to sets according their glutamate receptor : (Matthias 2003)
1- cells that expressed functional AMPA type glutamate receptors (GluRs) but lacked glutamate uptake
2- cells that possessed significant glutamate transport currents
Astrocytes are highly heterogeneous in physiology and function; two cell types identified by Matthias certainly exist, but they do not cover all the heterogeneity and astrocytes with similar properties may be present in other brain regions. Al in all we do not have enough data to properly classify astroglia.
Dear Hossein, Dr. Verkhratsky is the leading authority in this area, I follow his response. I would appreciate a discussion of astrocytes' mental functions based on their different physiological properties. What is the proper function of the varicose projection astrocytes exclusive to the human species (discovered by Oberheim et al.)? What is the relation of astrocytes and GABAergic neurons? Do GABAergic neurons induce astroglial calcium waves?
Dear professor verkhrasky
thanks a lot for your answer.
That's right. But would you please explain more abut the astrocytes are located in EC and DG of hippocamus which are involved in spatial memory?
Why do you think they are involved in spatial memory? this is pure speculation I am afraid. And as I said before we simply do not have enough data to characterize in detail astrocytes from different brain regions, so your question does not have an answer
this is my hypothisis. please see my paper and kindly let me know your comments about it.
"Mechanisms of hippocampal astrocytes mediation of spatial memory and theta rhythm by gliotransmitters and growth factors"
Furthermore I have new Idea about the relationship between astrocyte and place and grid cells.But I'm looking for evidence.
Dear Dr Junior
Thanks for your answer. Oberheim papers are very good and reading it would be useful for finding the answer of this question.
In your paper you find that certain factors possibly secereted by astrocytes affect several readouts which may (or may not) somehow reflect memory and learning. Astrocytes being homeostatic cells affect every process in the nervous system BUT it does not mean that they are the substrates of eg spatial memory.
Further I would suggest not to use the term "gliotransmitter"; astrocytes secrete several neurotransmitters (ATP, glutamate) or neuromodulators (D-Serine) or cytokines (TNFa); after all astrocytes are neural cells, are not they?
Thanks a lot for your comments. that's right.
In that paper, I tried to create a relationship between astrocytes and spatial memory.
I think that astrocytes have powerful tools for computation process. they can get data by their various kind of receptors and manage the neural network by secretion various substances as you mentioned. Further more they cooperate with each other by Ca signaling.
Indeed I think the astrocytes in the human body are like the men in the universe. They have common properties but for doing a specific job or management improved some of them. Astrocytes are manager and neurons are workers (this is my dream!!)
I would not be that excited; nervous tissue is composed of many cell types each of which is equally important; definitions such as "managers" and "workers" are greatly counterproductive; nervous system evolved through cellular specialisation; and each cell does its own function, which all are fundamental fro the function of the tissue as the whole. I personally believe hat the matter of "gliotransmision" has been rather hyped recently; astrocytes are not neurones and they are unlikely to be direct elements for cognition for example; at the same time neuropathology is mot likely gliopathology, because when homeostatic element does not work disease develops. When studying teh brain therefore I would advocate for a much more integrated approach which will reveal internal intercellular links that underlie the function without dividing these cells into bad or good, superior or inferior.
Dear professor Verkhratsky
your suggestions are completely right. All cells are important.
But I think astrocytes have tools for managing the neural system that other cells haven't it. Ca signaling ( local, global and spotty) and secretion of variety substances with different effects on function and performance of other cell (eg neuron) activities, are these tools. This is just a scientific sense.
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