The temporal dynamics of membrane voltage changes in neurons is controlled by ionic currents. These currents are characterized by two main properties: conductance and kinetics. The hyperpolarization-activated current (I h) strongly modulates subthreshold potential changes by shortening the excitatory postsynaptic potentials and decreasing their temporal summation. Whereas the shortening of the synaptic potentials caused by the I h conductance is well understood, the role of the I h kinetics remains unclear. Here, we use a model of the I h current model with either fast or slow kinetics to determine its influence on the membrane time constant (τm) of a CA1 pyramidal cell model. Our simulation results show that the I h with fast kinetics decreases τm and attenuates and shortens the excitatory postsynaptic potentials more than the slow I h. We conclude that the I h activation kinetics is able to modulate τm and the temporal properties of excitatory postsynaptic potentials (EPSPs) in CA1 pyramidal cells. To elucidate the mechanisms by which I h kinetics controls τm, we propose a new concept called “time scaling factor”. Our main finding is that the I h kinetics influences τm by modulating the contribution of the I h derivative conductance to τm.
All Science Journal Classification (ASJC) codes
- General Materials Science
- General Physics and Astronomy
- Physical and Theoretical Chemistry