Related Experiment Video
Updated: Feb 23, 2026
13:56
Modeling Biological Membranes with Circuit Boards and Measuring Electrical Signals in Axons: Student Laboratory Exercises
Published on: January 18, 2011
23.3K
Hyperpolarization-activated cyclic-nucleotide-gated channels potentially modulate axonal excitability at different
Dinushi Weerasinghe1, Parvathi Menon1,2, Steve Vucic3,2
1Department of Neurology, Westmead Hospital, Sydney, Australia; and.
Journal of Neurophysiology
|September 15, 2017
Summary
Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels influence sensory and motor axon excitability. Inward rectifying currents (Ih) increase in lower threshold axons, with different HCN channel isoforms contributing to these changes in sensory versus motor nerves.
Area of Science:
- Neuroscience
- Physiology
- Biophysics
Background:
- Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels are crucial for axonal excitability and implicated in neurological disorders.
- Inward rectifying currents (Ih) mediated by HCN channels influence resting membrane potential and neuronal function.
- Differences in human motor and sensory axon biophysical properties at varying thresholds are not well understood.
Purpose of the Study:
- To characterize sensory and motor axonal function at different thresholds in healthy human subjects.
- To investigate the role of HCN channels in mediating axonal excitability differences.
- To explore potential pathophysiological insights into peripheral neurological diseases.
Main Methods:
- Median nerve motor and sensory axonal excitability studies were performed on 15 healthy individuals.
- Threshold electrotonus (TEh) and current/voltage (I/V) gradients were measured at 20%, 40%, and 60% of maximum.
- Analysis focused on hyperpolarizing currents and their relationship to axonal threshold.
Main Results:
- Hyperpolarizing threshold electrotonus (TEh) was significantly increased in lower threshold sensory axons.
- The hyperpolarizing current/voltage (I/V) gradient was significantly increased in lower threshold motor axons.
- The minimum I/V gradient increased in both lower threshold motor and sensory axons.
Conclusions:
- Variations in HCN channel isoform kinetics likely explain the observed differences in motor and sensory axons.
- Increased inward rectifying currents (Ih) in lower threshold axons suggest distinct HCN channel contributions.
- Understanding HCN channel function in different axonal types may reveal novel therapeutic targets for neurological diseases.
Related Concept Videos
01:19The Role of Ion Channels in Neuronal Computation
4.0K
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential....
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential....
4.0K
01:29Excitatory and Inhibitory Effects of Neurotransmitters
13.6K
When an action potential reaches the presynaptic axon terminal, it releases neurotransmitters from the neuron into the synaptic cleft at a chemical synapse. The released neurotransmitter can be excitatory or inhibitory. The critical criteria commonly used to determine whether a molecule is a neurotransmitter at a chemical synapse are the molecule's presence in the presynaptic neuron. Second, its release is in response to strong presynaptic depolarization. And lastly, the presence of...
13.6K
01:41Action Potentials
144.1K
Overview
144.1K
01:30Ligand-Gated Ion Channel Receptor: Gating Mechanism
4.3K
Ligand-gated ion channels are transmembrane proteins that play a vital role in intercellular communication and functions of the nervous system. They allow the influx of ions across the membrane once the neurotransmitter binds, allowing the subsequent transmission of electrical excitation across the neurons. Other ligand-gated ion channels, like the γ-aminobutyric acid (GABA) receptor, permit anions like chloride into the cells on the binding of the GABA molecule. Their entry into the cell...
4.3K
01:28Action Potential: Phases of Stimulation
13.1K
The action potential is a complex electrical event that occurs in excitable cells, such as neurons and muscle cells. It consists of several distinct phases, each with specific characteristics.
Resting Phase:
In this phase, the cell's membrane is at its resting potential, typically around -70 millivolts (mV) for neurons. Inside the cell, there is a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+). Voltage-gated sodium channels are closed, and...
Resting Phase:
In this phase, the cell's membrane is at its resting potential, typically around -70 millivolts (mV) for neurons. Inside the cell, there is a higher concentration of potassium ions (K+) and a lower concentration of sodium ions (Na+). Voltage-gated sodium channels are closed, and...
13.1K
01:26Voltage-gated Ion Channels
11.3K
Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
11.3K