Sensory transduction in peripheral nerve axons elicits ectopic action potentials
Tal Hoffmann1, Susanne K Sauer, Raymund E Horch
1Institute for Physiology and Pathophysiology, University Medical Center, University of Erlangen-Nuremberg, D-91054 Erlangen, Germany. diskin@physiologie1.uni-erlangen.de
Summary
Peripheral nerve axons share heat sensitivity with skin receptors, potentially causing ectopic discharge and pain during inflammation. This study investigated axonal activation and sensory properties in mouse C-fibers.
Area of Science:
- Neuroscience
- Pain Research
- Sensory Physiology
Background:
- Unmyelinated axons release neuropeptides in response to noxious stimuli.
- Inflammatory mediators sensitize axons via the transient receptor potential vanilloid receptor-1 (TRPV1) channel.
- The role of ectopic action potential generation in neuropathic pain remained unclear.
Purpose of the Study:
- To investigate whether axonal sensitization by inflammatory mediators is accompanied by ectopic generation of action potentials.
- To compare sensory properties of peripheral axons with their cutaneous terminals.
- To utilize propagated action potentials as an index of axonal activation.
Main Methods:
- Used an isolated mouse skin-nerve preparation.
- Performed single-fiber recordings from 51 mechanosensitive mouse C-fibers.
- Measured responses to graded heating of cutaneous receptive fields and the saphenous nerve.
Main Results:
- A majority of polymodal nociceptors responded to graded heating of both receptive fields and the nerve.
- Axonal heat responses paralleled receptive field responses in thresholds and discharge rates.
- Axonal mechanosensitivity was poor, and noxious cold sensitivity was rarely encountered.
Conclusions:
- Peripheral nerve axons possess sensory transduction capacities for noxious heat, similar to skin nociceptive terminals.
- Axons do not exhibit similar sensitivity to mechanical and cold stimuli.
- Axonal heat sensitivity may lead to ectopic discharge and pain if the threshold drops to body temperature during inflammation.
More Related Videos
Related Concept Videos
01:41Action Potentials
Overview
01:14Action Potential
Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
01:14Action Potential
Neurons communicate by firing action potentials—the electrochemical signal that is propagated along the axon. The signal results in the release of neurotransmitters at axon terminals, thereby transmitting information to the nervous system. An action potential is a specific "all-or-none" change in membrane potential that results in a rapid spike in voltage.
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
Membrane potential in neurons
Neurons typically have a resting membrane potential of about -70 millivolts (mV). When they receive...
01:23Propagation of Action Potentials
The propagation of an action potential refers to the process by which a nerve impulse, or "action potential," travels along a neuron.
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...
Neurons (nerve cells) have a resting membrane potential, with a slightly negative charge inside compared to outside. This is maintained by ion channels, such as sodium (Na+) and potassium (K+) channels, which control the flow of ions. When a stimulus, like a touch or a signal from another neuron, triggers the neuron, sodium channels open, allowing sodium ions to...
01:28Action Potential: Phases of Stimulation
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...
01:19The Role of Ion Channels in Neuronal Computation
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.