Sustained K<SUP>+</SUP> Outward Currents are Sensitive to Intracellular Heteropodatoxin2 in CA1 Neurons of Organotypic Cultured Hippocampi of Rats
Sustained K<SUP>+</SUP> Outward Currents are Sensitive to Intracellular Heteropodatoxin2 in CA1 Neurons of Organotypic Cultured Hippocampi of Rats
- Sung-Cherl Jung Su-Yong Eun
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제16권 제5호
- 등재여부 : KCI등재
- 2012.01
- 343 - 348 (6 pages)
Blocking or regulating K<sup>+</sup> channels is important for investigating neuronal functions in mammalian brains, because voltage-dependent K<sup>+</sup> channels (Kv channels) play roles to regulate membrane excitabilities for synaptic and somatic processings in neurons. Although a number of toxins and chemicals are useful to change gating properties of Kv channels, specific effects of each toxin on a particular Kv subunit have not been sufficiently demonstrated in neurons yet. In this study, we tested electrophysiologically if heteropodatoxin2 (HpTX<sub>2</sub>), known as one of Kv4-specific toxins, might be effective on various K<sup>+</sup> outward currents in CA1 neurons of organotypic hippocampal slices of rats. Using a nucleated-patch technique and a pre-pulse protocol in voltage-clamp mode, total K<sup>+</sup> outward currents recorded in the soma of CA1 neurons were separated into two components, transient and sustained currents. The extracellular application of HpTX<sub>2</sub> weakly but significantly reduced transient currents. However, when HpTX<sub>2</sub> was added to internal solution, the significant reduction of amplitudes were observed in sustained currents but not in transient currents. This indicates the non-specificity of HpTX<sub>2</sub> effects on Kv4 family. Compared with the effect of cytosolic 4-AP to block transient currents, it is possible that cytosolic HpTX<sub>2</sub> is pharmacologically specific to sustained currents in CA1 neurons. These results suggest that distinctive actions of HpTX<sub>2</sub> inside and outside of neurons are very efficient to selectively reduce specific K<sup>+</sup> outward currents.