CORRELATION OF OPEN CELL-ATTACHED AND EXCISED PATCH-CLAMP TECHNIQUES

The excised patch clamp configuration provides a unique technique for some types of single channel analyses, but maintenance of stable, long-lasting preparations may be confounded by rundown and/or rapid loss of seal, Studies were performed on the amiloride-sensitive Na+ channel, located on the apical surface of A, cells, to determine whether the nystatin-induced open cell-attached patch could serve as an alternative configuration. Compared to excised inside-out patches, stable preparations were achieved more readily with the open cell-attached patch (9% vs, 56% of attempts), In both preparations, the current voltage (I-V) relation was linear, current amplitudes were equal at opposite equivalent clamped voltages, and E(rev) was zero in symmetrical Na+ solutions, indicating similar Na+ activities on the cytosolic and external surfaces of the patch. Moreover, there was no evidence that nystatin altered channel activity in the patch because slope conductance (3-4pS) and E(rev) (75 mV), when the bath was perfused with a high K:low Na solution (E(Na) = 80 mV), were nearly equal in both patch configurations, Our results therefore indicate that the nystatin-induced open cell-attached patch can serve as an alternative approach to the excised inside-out patch when experiments require modulation of univalent ions in the cytosol.