Figure 6.

The measured pH and isoflurane sensitivity of motoneurons are well described by curves derived from estimates of the relative contributions of TASK homodimers and heterodimers to native currents. Data from experiments with combined application of ruthenium red and isoflurane were used to estimate the fractional contribution of TASK-1 homodimers, TASK-3 homodimers, and TASK-1/TASK-3 heterodimers to the whole-cell pH-sensitive current in motoneurons (TASK-1, ∼14%; TASK-3, ∼34%; TASK heterodimers, ∼52%; see Results). These fractional contributions were applied as weighting factors to the pH and isoflurane sensitivity curves determined for cloned TASK channels, which were then summed and fitted to determine a predicted pH (A) and isoflurane (B) sensitivity of motoneuronal TASK-like currents. In both cases, these predicted sensitivity curves (dashed lines) closely matched data obtained from motoneurons (circles).