Biomedical Research

Müller glial cells of the vertebrate retina express purinergic P2 receptors; activation of these receptors causes an increase of the intracellular free calcium concentration and a subsequent activation of calcium-dependent potassium channels in the plasma membranes. The expres-sion of these receptors varies among the animal species. Müller cells of all species investigated so far express metabotropic P2Y receptors while human Müller cells additionally express ionotropic P2X7 receptors. The expression level of functional purinergic receptors in Müller cells of the rabbit retina is dependent on the developmental stage. At the early postnatal stage, the vast majority of immature radial glial cells show calcium responses upon exposure to ex-tracellular ATP whereas in the adult retina, only a minority of Müller cells shows such re-sponses. However, in experimental proliferative retinal diseases, the ATP responsiveness in-creases significantly in correlation to alterations of the potassium conductances of the mem-brane. A similar disease-dependent up-regulation was found in human Müller cells, in respect to the expression of functional P2X7 receptors. Purinergic receptors are suggested to be impli-cated in the regulation of both retinal precursor cell proliferation in the developing retina and reactive Müller cell proliferation in the diseased adult retina.

Author(s): A. Bringmann, T. Pannicke, M. Francke, I. Milenkovic, M. Weick, O. Uckermann, S. Uhlmann, P. Wiedemann and A. Reichenbach
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