Expression of the dominant negative Kv4.2DN in rat visual cortical pyramidal neurons selectively eliminated the fast transient outward K+ current (IA), resulting in prolonged action potential durations and altered repetitive firing.
Does the expression of a dominant negative Kv4.2 subunit alter action potential waveforms and repetitive firing in rat visual cortical pyramidal neurons?
Kv4 alpha subunits encode IA channels, which are essential for shaping action potential waveforms and controlling repetitive firing in visual cortical pyramidal neurons.
Absolute Event Rate: 8.4% vs 3.8%
p-value: p=<0.01
A molecular genetic approach was exploited to directly test the hypothesis that voltage-gated K+ (Kv) channel pore-forming (alpha) subunits of the Kv4 subfamily encode the fast transient outward K+ current (IA) in cortical pyramidal neurons and to explore the functional role of IA in shaping action potential waveforms and in controlling repetitive firing in these cells. Using the biolistic gene gun, cDNAs encoding a mutant Kv4.2 alpha subunit (Kv4.2W362F), which functions as a dominant negative (Kv4.2DN), and enhanced green fluorescent protein (EGFP) were introduced in vitro into neurons isolated from postnatal rat primary visual cortex. Whole-cell voltage-clamp recordings obtained from EGFP-positive pyramidal neurons revealed that IA is selectively eliminated in cells expressing Kv4.2DN. The densities and properties of the other Kv currents are unaffected. In neurons expressing Kv4.2DN, input resistances are increased and the (current) thresholds for action potential generation are decreased. In addition, action potential durations are prolonged, the amplitudes of afterhyperpolarizations are reduced, and the responses to prolonged depolarizing inputs are altered markedly in cells expressing Kv 4.2DN. At low stimulus intensities, firing rates are increased in Kv4.2DN-expressing cells, whereas at high stimulus intensities, Kv4.2DN-expressing cells adapt strongly. Together, these results demonstrate that Kv4alpha subunits encode IA channels and that IA plays a pivotal role in shaping the waveforms of individual action potentials and in controlling repetitive firing in visual cortical pyramidal neurons.
Yuan et al. (Wed,) conducted a other in Normal physiology (rat visual cortical pyramidal neurons). Kv4.2DN (dominant negative mutant) transfection vs. EGFP transfection alone was evaluated on Action potential duration at 50% repolarization (APD50) (p=<0.01). Expression of the dominant negative Kv4.2DN in rat visual cortical pyramidal neurons selectively eliminated the fast transient outward K+ current (IA), resulting in prolonged action potential durations and altered repetitive firing.