Patch-clamp recordings on rat cardiac muscle slices.

Thin slices (100-200 microns) from cardiac ventricles of newborn (1-14 days old) rats were used for patch-clamp recordings. High resistance seals (greater than 10 GOhms) could be obtained on this preparation without enzymatic treatment of tissue. Resting potential for cardiac fibres, measured in whole-cell configuration, ranged between -30 and -65 mV. Averaged sodium currents and inward rectifying potassium single-channel currents, recorded in cell-attached mode, displayed similar features to those previously reported for isolated rat ventricular cells. Application of patch-clamp techniques to cardiac slices allows single-channel recordings without complicated procedures of cell isolation. Moreover, possible alteration of channel properties caused by proteolytic enzymes can be avoided. This technique provides a new tool for studying electrophysiological properties of heart cells in situ.