A NOVEL METHOD FOR RECORDING WHOLE-CELL AND SINGLE-CHANNEL CURRENTS FROM DIFFERENTIATING CEREBELLAR GRANULE CELLS IN-SITU

A preparation procedure is described yielding very thin tissue layers (1-3 cells) of the rat cerebellum. One-week-old rat cerebellum was emb edded in agarose and cut in 1 mm slices, which then were mounted by a fresh fibrin preparation on the bottom of a culture dish. After coagul ation of the fibrin the slice was gently lifted, leaving a thin finger print-like layer of cells on the bottom of the dish. Individual cells could be identified by their topographical positions. From these prepa rations patch-clamp recordings were made of cells in the external and the internal granule layer and of migrating cells. Whole-cell currents of cells in the external granule layer, recorded using the perforated -patch method, show that these neuroblasts already possess a full comp lement of ionic currents, consisting of a transient sodium current and a transient and a sustained potassium current. Whereas the potassium currents are predominant, the maximum sodium peak currents are minute (42 +/- 5 pA, mean +/- S.E.M., n = 21), i.e. too small for generating action potentials. There were no significant differences between cells of the external and the internal granule layer. The ionic channels pa ssing these currents were identified and characterized in single-chann el studies on cell-attached patches. Two types of potassium channel we re found: a non-inactivating channel with a single-channel conductance of 21 pS and an inactivating channel with a conductance of 6 pS.