MODEL-BASED ON EXTRACELLULAR POTASSIUM FOR SPONTANEOUS SYNCHRONOUS ACTIVITY IN DEVELOPING RETINAS

Waves of action-potential bursts propagate across the ganglion-cell su rface of isolated developing retinas. It has been suggested that the r ise of extracellular potassium concentration following a burst of acti on potentials in a cell may underlie these waves by depolarizing neigh bor cells. This suggestion is sensible for developing tissues, since t heir glial system is immature. We tested whether this extracellular-po tassium suggestion is feasible. For this purpose, we built a realistic biophysical model of the ganglion-cell layer of the developing retina . Simulations with this model show that increases of extracellular pot assium are sufficiently high (about fourfold) to mediate the waves con sistently with experimental physiological and pharmacological data. Ev en if another mechanism mediates the waves, these simulations indicate that extracellular potassium should significantly modulate the waves' properties.