Figure 9.

Reversal potenial and activation and deactivation kinetics of the K⁺ currents sensitive to polyclonal anti-Kv2.1 or ScTx (600 nM) Time constants were obtained by fitting currents with a single exponential function. A, an example of tail currents sensitive to 600 nm ScTx (P20). The tail currents were elicited by a series of different voltages stepped down from a 200 ms activating potential step of –10 mV (inset). B, both the ScTx-sensitive and –insensitive current components reversed polarity near E_K (3 mm K⁺). The reversal potential also shifted in a Nernstian manner with elevated extracellular K⁺ (50 mm K⁺). These data indicate that the channels underlying the ScTx-sensitive and –insensitive currents are very potassium selective. C, activation and deactivation time constants for the ScTx-sensitive and ScTx-insensitive currents. ScTx-sensitive and –insensitive currents have similar kinetics at negative potentials, with the ScTx-insensitive currents being slower at potentials depolarized to ∼−20 mV. D, the activation and deactivation time constants of the ScTx-sensitive and the anti-Kv2.1-sensitive currents were very similar over the entire voltage range tested.