Müller cells ‐ structural and physiological functions

In 1851, Heinrich Müller discovered what he called ‘radial fibers’ and what we now call Müller cells, as the principal glial cells of the vertebrate retina. During the past decades it became evident that they are essential constituents of the retinal tissue. Müller cells appear to constitute the ‘core’ of columnar units of clonally and functionally related groups of neurons. Their primary function is to support neuronal functioning (by increasing the signal‐to‐noise ratio of information processing) and survival (by maintaining a metabolic ‘symbiosis’ with the neurons). Much of this dual role of glial cells involves specific homeostatic mechanisms. Current progress in the field is achieved by the application of various novel experimental methods (cellular electrophysiology, imaging methods, optical and biomechanical measurements, and others). Herewith it was shown that Müller cells increase the signal‐to‐noise ratio of retinal information processing by, for instance, (i) guiding the light towards the photoreceptor cells, (ii) removing excess neurotransmitter molecules from extracellular space, and (iii) performing an efficient clearance of excess extracellular potassium ions after neuronal excitation.