Outward-rectifying K+ current

Delayed-rectifier K+ channels activate with a delay and mediate outwardly-rectifying K+ currents. These channels may make a significant contribution to the icpolarizing phase of nervous action potentials. 

IISVl induced loss of Na currents was similar for both TTX-S and TTX-R currents. The effects of HSV-1 infection on voltage-gated ion channel function appeared to be restricted to Na channels as Ca- currents and outwardly rectifying K currents were not significantly changed after HSV-1 infection in vitro. 

The electrophysiology of a number of plant cells have been studied and characterized. A plasmalemmal proton pump, a hydrogen hloride symporter, inward- and outward-rectifying K+ currents, and a chloride channel were modeled in the equations representing electrical activity in Egeria densa Planchon by Buschmann et al. [1996]. 

Of the many channels that exist in cardiac muscle, we will provide an overview of only those conductances which carry most of the outward repolarising current and that are important in understanding the basis for development of the CIPA paradigm for SP. These include only the transient outward (/to) K" current, the delayed rectifier (/r) current and its components that contribute predominantly during the plateau and early stages of repolarisation of the AP and the inward rectifier (/rir) channels. 

Inward Rectifier K+ Channels. Figure 2 High [K+] inside cells relative to outside results in normal rectification, whereby outward (positive by convention) potassium currents (/) when cells are depolarized (is positive relative to EK), are biggerthan inward (negative) currents at hyperpolarized (negative) voltages. Inward or anomalous rectifiers show strong or weak inward rectification whereby outward currents are smaller than inward currents. 

Cardiac APD is controlled by a fine balance between inward and outward currents in the repolarization phase. Since outward K+ currents, especially the delayed rectifier repolarizing current, IK (which is the sum of two kinetically and pharmacologically distinct types of K+ currents a rapid, 1k and a slow, IKs, component), play an important role during repolarization and in determining the configuration of the action potential, small changes in conductance can significantly alter the effective refractory period, hence the action potential duration. 

In addition to its action on an inward rectifying current, a second K+ conductance activated by 5HT1A receptors has been reported on prepositus hypoglossi neurons (64), where both /IR and /OR (an outwardly rectifying slowly activated K current) contribute to generating the current that underlies inhibitory postsynap-tic potentials (IPSPs). 

Plateau phase in which a slow influx of Ca2+ (ICa.L) is balanced by a late-appearing outward K+ current (the delayed rectifier current IK). 

E-4031 and the cation (Main et al. 1998)./KurOrthe/Tvl.5 channel is present in human atrial tissue. It is outwardly rectifying and highly selective for K". Like other Ky channels it activates during the plateau phase of the cardiac AP and is distinguished from related A v channels by its sensitivity to very low concentrations of extracellular 4-AP. /r sIow is another distinct K f channel represented by K l.2 expression (Nerboime 2000). It is sensitive to block by very low concentrations of 4-AP but unlike /kut this current is sensitive to nanomolar concentrations of dendrotoxin (DTX) and thus may be designated as /k,dtx (Nerbonne 2000). 

Inwardly rectifying potassium (Kir) currents were first characterized decades ago in skeletal and cardiac muscle fibers. Also initially referred to as anomalous rectifiers, these currents were named for their unique characteristic of preferentially conducting inward currents, while outward currents were inhibited (Hutter and Noble 1960 Noble 1962). This trait contrasted with the outward rectification and intrinsic voltage dependence of the classic voltage-dependent K (Kv) currents in excitable... 

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