Electrophysiology of rabbit Muller (glial) cells in experimental retinal detachment and PVR

PURPOSE. To determine the electrophysiological properties of Muller (glial) cells from experimentally detached rabbit retinas. METHODS. A Stable local retinal detachment was induced by subretinal inject ion of a sodium hyaluronate solution. Muller cells were acutely dissociated and studied by the whole-cell voltage-clamp technique. RESULTS. The cell membranes of Muller cells from normal retinas were domina ted by a large inwardly rectifying potassium ion (K+) conductance that caus ed a low-input resistance (<100 M<Omega>) and a high resting membrane poten tial (-82 +/- G mV). During the first week after detachment, the Muller cel ls became reactive as shown by glial fibrillary acidic protein (GFAP) immun oreactivity, and their inward currents were markedly reduced, accompanied b y an increased input resistance (>200 MR). After 3 weeks of detachment, the input resistance increased further (>300 Mn), and some cells dis played si gnificantly depolarized membrane potentials (mean -69 +/- 18 mV). When PVR developed (in 20% of the cases) the inward K) currents were virtually compl etely eliminated. The input resistance increased dramatically (>1000 MR), a nd almost all cells displayed strongly depolarized membrane potentials (-44 +/- 16 mV). CONCLUSIONS. Reactive Muller cells are characterized by a severe reduction of their K+ inward conductance. accompanied by depolarized membrane potenti als. These changes must impair physiological glial functions, such as neuro transmitter recycling and K+ ion clearance. Furthermore, the open probabili ty of certain types of voltage-dependent ion channels (e.g., Ca2+-dependent K+ maxi channels) increases that may be a precondition for Muller cell pro liferation, particularly in PVR when a dramatic downregulation of both inwa rd current density and resting membrane potential occurs.