Figure 2.

The anomalous rectification and the IA-like delayed repolarization observed during a brief membrane hyperpolarization exhibit voltage-dependent properties. A: In a nondischarging DA neuron, progressive steady-state hyperpolarization of the membrane by current injection (bottom trace) increased the amplitude of the anomalous rectification observed at the initiation of the hyperpolarizing pulse and caused a decrease in the IA-like delayed repolarization observed at the offset of the pulse. B, C: Injection of a hyperpolarizing current pulse into this tetrodotoxin (TTX)- and tetraethylammonium (TEA)-treated DA neuron reveals the delayed repolarization at the offset of the pulse. Although the form of the delayed repolarization is similar to that described for the IA conductance described elsewhere, it does not exhibit the characteristic sensitivity to administration of 4-aminopyridine (4-AP). Concentrations of 4-AP: 1 = control; 2 = 5 mM; 3 = 20 mM. (From ref. 29, with permission.)

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published 2000