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Updated: Apr 17, 2026
In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing
Published on: February 6, 2018
Effects of anesthetic agents on in vivo axonal HCN current in normal mice
Yusuke Osaki1, Hiroyuki Nodera1, Chimeglkham Banzrai1
1Department of Neurology, Tokushima University, Tokushima, Japan.
Objective:
The objective was to study the in vivo effects of anesthetic agents on peripheral nerve excitability.
Methods:
Normal male mice were anesthetized by either isoflurane inhalation or a combination of medetomidine, midazolam, and butorphanol intraperitoneal injection ("triple agents"). Immediately after induction, the tail sensory nerve action potential was recorded and its excitability was monitored.
Results:
Under both anesthetic protocols, there was an interval excitability change by long hyperpolarizing currents. There was greater threshold reduction approximately 30min post induction, in comparison to immediately post induction. Other excitability parameters were stable over time. Modeling suggested interval suppression of internodal H conductance or leak current.
Conclusions:
Anesthetic agents affected responses to long hyperpolarizing currents.
Significance:
Axonal excitability during intraoperative monitoring may be affected by anesthetic agents. Interpretation of interval excitability changes under anesthesia requires caution, especially with long hyperpolarizing currents.
Insights
Anesthetic agents alter peripheral nerve excitability in mice, particularly in response to long hyperpolarizing currents. This suggests caution is needed when interpreting nerve activity during anesthesia.
Area of Science:
- Neuroscience
- Anesthesiology
- Physiology
Background:
- Peripheral nerve excitability is crucial for neural function.
- Anesthetic agents are widely used but their precise effects on nerve physiology in vivo are not fully understood.
- Understanding these effects is vital for accurate intraoperative monitoring.
Purpose of the Study:
- To investigate the in vivo effects of common anesthetic agents on peripheral nerve excitability.
- To determine how different anesthetic protocols influence nerve responses to electrical stimulation.
Main Methods:
- Normal male mice were subjected to two anesthetic protocols: isoflurane inhalation or a combination of medetomidine, midazolam, and butorphanol (triple agents).
- Peripheral nerve excitability was assessed by recording tail sensory nerve action potentials immediately after anesthetic induction and at intervals thereafter.
- Excitability was monitored using standardized electrophysiological techniques, including responses to long hyperpolarizing currents.
Main Results:
- Both anesthetic protocols induced interval changes in nerve excitability when subjected to long hyperpolarizing currents.
- A greater reduction in nerve excitation threshold was observed approximately 30 minutes post-induction compared to immediately after induction.
- Modeling suggested that these interval changes might be due to the suppression of internodal H conductance or leak currents.
Conclusions:
- Anesthetic agents significantly affect peripheral nerve responses to long hyperpolarizing currents.
- Axonal excitability during intraoperative monitoring can be influenced by anesthetic agents.
- Careful interpretation of interval excitability changes under anesthesia is necessary, especially when using long hyperpolarizing currents.
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