CHARACTERIZATION OF STRETCH-ACTIVATED ION CHANNELS IN CULTURED ASTROCYTES

The presence of a stretch-activated channel in rat cerebellar astrocyt es in culture is described. This stretch-sensitive channel is K+-selec tive and its open probability increases with suction following a Boltz mann-like distribution with half activation at 45 mm Hg. Kinetic analy sis of the single-channel data indicated that there are two open and t wo closed states and that the shortest time constants of both open and closed states are the most sensitive to suction. A symmetrical two-ba rrier-one-site permeation model can quantitatively describe the inward rectification of the single-channel current to voltage relations. It is suggested that this stretch-activated channel plays a role in the r egulatory volume response of astrocytes to hyposmotic conditions.