NEURON Tutorial #20

Goals: Examine The Influence of Q10, The Size of Injected Current, and gbar_h

Specific Aims:

1. Examine the influence of Q10 on impedance magnitude and voltage lag.
2. Examine the influence of Q10 on activation and inactivation time constant.
3. Examine the influence of the size of injected current on impedance magnitude and voltage lag.
4. Examine the influence of gbar_h on impedance magnitude and voltage lag.

Summary:

1. Q10 on Impedance Magnitude and Voltage Lag

Conditions

e_pas = -74 (mV)
gbar_h = 2e-5 (S/cm2)
Altomare's model (2001)

Notes

Smaller Q10 produces results more similar to physiological data. Magee's data suggested Q10 of Ih is about 5. The parameters of this simulation are based on Altomare's HCN1 model. Since HCN2 is slower than HCN1, a better fit with Q10 = 2.5 might be due to that the native Ih contains both HCN1 and HCN2.

2. Q10 on Activation and Inactivation Time Constant

Conditions

e_pas = -74 (mV)
gbar_h = 2e-5 (S/cm2)
Altomare's model (2001)

Notes

Larger Q10 leads to faster time constant.

3. The Size of Injected Current Amplitude on Impedance Magnitude and Voltage Lag

Conditions

Ih model in Sonia's paper
e_pas = -70 (mV)
gbar_h = 4e-5 (S/cm2)

Notes

The larger the size of injected current, the larger the difference in the impedance magnitude between peaks and troughs.
The larger the size of injected current, the larger the difference in the voltage lag between falling and rising edges.

4. The Influence of gbar_h on Impedance Magnitude and Voltage Lag

Conditions

Ih model in Sonia's paper
gbar_h = 2e-5 (S/cm2), e_pas = -67.5 (mV)
gbar_h = 4e-5 (S/cm2), e_pas = -70.0 (mV)
gbar_h = 8e-5 (S/cm2), e_pas = -75.0 (mV)

Notes

The differences in impedance magnitude and voltage lag between depolarization and hyperpolarization are larger when gbar_h is close to the median.