Figure 2
IIRK and IhERG in astrocytoma cells. (A) Representative whole-cell IIRK traces, measured from glioma cells, by using the procedure described in Figure 1. The stimulation protocol is shown in the inset. The conditioning step at 0 mV lasted 10 s. Holding potential was −60 mV. IIRK was isolated by subtracting the current recorded in the presence of Cs+ from the total current. In this astrocytoma case, no evidence for IhERG was found. The panel on the right plots the average normalised peak currents as a function of the test potential, from four experiments. (B) Whole-cell IhERG traces, from a different astrocytoma case, elicited by using the same stimulation protocol illustrated in panel A. IhERG was isolated by subtracting the current obtained in the presence of 1 μ M WAY from the total current. The panel on the right plots the corresponding I/V curve. Data points are average normalised peak currents plotted as a function of the test potential. Currents were measured in five cells from the same case. (C) Whole-cell tail IhERG at −120 mV, elicited from 3 s conditioning pulses from −60 to + 40 mV, as shown in the inset. Pure IhERG was isolated by applying 1 μ M WAY. Peak tail currents were estimated by extrapolating the currents at −120 mV to the start of pulse (as indicated in the ‘Control–WAY’ panel). In this way, we corrected for the partial deactivation occurring before the fast recovery from inactivation is complete. Data points are average maximal tail current values at −120 mV, plotted as a function of the conditioning potential, measured in three experiments from the same glioma case.
