Spinal Evoked Compound Action Potentials in Rats With Clinically Relevant Stimulation Modalities

Area of Science:

• Neuroscience
• Biomedical Engineering
• Pain Research

Background:

• Rats are crucial models for translational pain and spinal cord stimulation (SCS) research.
• Stimulation amplitudes in rat SCS studies are often set relative to visual motor threshold (vMT), unlike human studies which may use evoked compound action potential thresholds (ECAPTs).
• Characterizing ECAPTs, evoked compound muscle action potential thresholds (ECMAPTs), and vMTs is essential for standardizing SCS research parameters in rats.

Purpose of the Study:

• To characterize ECAPTs, ECMAPTs, and vMTs in rats using clinically relevant SCS modalities.
• To compare different methods of programming SCS amplitudes in a rat model.
• To assess the feasibility of ECAP recording in rats during SCS.

Main Methods:

• Ten anesthetized rats were implanted with epidural SCS leads for lumbar stimulation and thoracic ECAP sensing.
• Two SCS paradigms were used: 50-Hz SCS with varying pulse widths (PWs) and a multiplexed low-rate program (LRP)/high-rate program (HRP).
• Amplitudes were increased to vMT or ECAPT, and ECAPTs, ECMAPTs, and vMTs were recorded.

Main Results:

• vMTs were approximately 3 times greater than ECAPTs and marginally greater than ECMAPTs across tested PWs.
• A negligible increase in LRP ECAP was observed as HRP amplitudes increased in the second paradigm.
• These findings indicate consistent neural activation levels with different amplitude programming methods.

Conclusions:

• SCS amplitudes programmed relative to vMT or ECMAPT show reasonable neural activation in anesthetized rats.
• The study demonstrates the feasibility of ECAP recording in rats with multiplexed HRP SCS.
• These results support the use of ECAPTs for programming SCS amplitudes in rat research, enhancing translational relevance.