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Subthreshold membrane oscillations underlying integer multiples firing from injured sensory neurons
1Institute of Neuroscience, Fourth Military Medical University, Xi'an 710032, P.R. China.
Neuroreport
|May 8, 2001
Summary
Injured dorsal root ganglion (DRG) neurons exhibit integer multiples firing (IMF) due to regular subthreshold membrane oscillations (SMOs). Tetrodotoxin (TTX) application reveals mechanisms involving SMO amplitude and action potential threshold changes.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Injured dorsal root ganglion (DRG) neurons can exhibit abnormal spontaneous firing patterns.
- Integer multiples firing (IMF) is a recently identified temporal firing pattern in these neurons.
Purpose of the Study:
- To investigate the underlying mechanism of integer multiples firing (IMF) in injured rat dorsal root ganglion (DRG) neurons.
- To explore the role of subthreshold membrane oscillations (SMOs) in the generation of IMF.
Main Methods:
- Intracellular recordings were performed on spontaneously discharging injured rat DRG A-neurons.
- Analysis of interspike interval (ISI) time series and scatter maps.
- Local application of tetrodotoxin (TTX), a sodium channel antagonist, to induce firing pattern changes.
Main Results:
- Eight out of 64 recorded neurons displayed IMF.
- IMF neurons consistently showed regular subthreshold membrane oscillations (SMOs) with stable amplitude and frequency.
- IMF could be induced from periodic firing neurons by TTX, accompanied by marked variations in SMO amplitude.
- Some SMOs failed to trigger action potentials despite exceeding threshold, or triggered them even when below the threshold of nearby spikes.
Conclusions:
- Regular subthreshold membrane oscillations (SMOs) in injured DRG A-neurons are the basis for integer multiples firing (IMF).
- The transformation from periodic firing to IMF induced by TTX involves either a decrease in SMO amplitude or an elevation of the action potential threshold.