Impact of the activation rate of the hyperpolarization- activated current Ih on the neuronal membrane time constant and synaptic potential duration

• Published in: The European physical journal. ST, Special topics Vol. 230; no. 14-15; pp. 2951 - 2961
• Main Authors: Ceballos, Cesar C., Pena, Rodrigo F. O., Roque, Antonio C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2021; Springer Nature B.V
• Subjects: Atomic; Classical and Continuum Physics; Condensed Matter Physics; Dynamical Phenomena in Complex Networks: Fundamentals and Applications; Kinetics; Materials Science; Measurement Science and Instrumentation; Membranes; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Regular Article; Scaling factors; Time constant
• DOI: 10.1140/epjs/s11734-021-00176-z
• EISSN: 1951-6401
• ISSN: 1951-6355

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 (
τ
m
)
of a CA1 pyramidal cell model. Our simulation results show that the
I
h
with fast kinetics decreases
τ
m
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
τ
m
and the temporal properties of excitatory postsynaptic potentials (EPSPs) in CA1 pyramidal cells. To elucidate the mechanisms by which
I
h
kinetics controls
τ
m
, we propose a new concept called “time scaling factor”. Our main finding is that the
I
h
kinetics influences
τ
m
by modulating the contribution of the
I
h
derivative conductance to
τ
m
.