Hysteresis in voltage gating of HCN channels (Elinder et al 2006, Mannikko et al 2005)

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Accession:82758
We found that HCN2 and HCN4 channels expressed in oocytes from the frog Xenopus laevis do not display the activation kinetic changes that we (previously) observed in spHCN and HCN1. However, HCN2 and HCN4 channels display changes in their tail currents, suggesting that these channels also undergo mode shifts and that the conformational changes underlying the mode shifts are due to conserved aspects of HCN channels. With computer modelling, we show that in channels with relatively slow opening kinetics and fast mode-shift transitions, such as HCN2 and HCN4 channels, the mode shift effects are not readily observable, except in the tail kinetics. Computer simulations of sino-atrial node action potentials suggest that the HCN2 channel, together with the HCN1 channel, are important regulators of the heart firing frequency and that the mode shift is an important property to prevent arrhythmic firing. We conclude that although all HCN channels appear to undergo mode shifts – and thus may serve to prevent arrhythmic firing – it is mainly observable in ionic currents from HCN channels with faster kinetics. See papers for more and details.
References:
1 . Elinder F, Mannikko R, Pandey S, Larsson HP (2006) Mode shifts in the voltage gating of the mouse and human HCN2 and HCN4 channels J. Physiol. 575.2:417-431 [PubMed]
2 . Mannikko R, Pandey S, Larsson HP, Elinder F (2005) Hysteresis in the voltage dependence of HCN channels: conversion between two modes affects pacemaker properties. J Gen Physiol 125:305-26 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Channel/Receptor;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s): I Na,t; I L high threshold; I T low threshold; I K; I M; I h;
Gap Junctions:
Receptor(s):
Gene(s): HCN2; HCN4;
Transmitter(s):
Simulation Environment: QBasic/QuickBasic/Turbo Basic;
Model Concept(s): Ion Channel Kinetics; Action Potentials; Heart disease;
Implementer(s): Elinder, Fredrik [fredrik.elinder at ibk.liu.se];
Search NeuronDB for information about:  I Na,t; I L high threshold; I T low threshold; I K; I M; I h;
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modeshift
readme.txt
SAN-MODE.BAS
                            
This is the readme.txt for the turbobasic program associated with the publications:

SA-NODE ACTION POTENTIAL" BY FREDRIK ELINDER, LINK PINGS UNIVERSITET
REFERENCES: MNIKK, PANDEY, LARSSON & ELINDER. 2005. J GEN PHYSIOL 125:305-326
            ELINDER, MNIKK, PANDEY & LARSSON. 2006. J PHYSIOL 575:417-431
  UPDATED SEPTEMBER 13, 2006
  BASED ON THE MODEL BY ZHANG ET AL., 2000, AM J PHYSIOL 279:H397-H421
  DIFFERENCES FROM ZHANG ET AL: NEW DESCRIPTION OF HCN + CORRECTION OF EQ 42

This model file, SAN-MODE.BAS was supplied by Fredrik Elinder.

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