Related Experiment Video
Updated: Oct 27, 2026
The Ex vivo Preparation of Spinal Cord Slice for the Whole-Cell Patch-Clamp Recording in Motor Neurons During Spinal Cord Stimulation
Published on: September 8, 2023
Factors Affecting Evoked Compound Action Potential Threshold Estimation in Preclinical Models of Spinal Cord
Eline M Versantvoort1, Kimberley Ladner1, Dave Mugan2
1Newcastle University, School of Pharmacy and Translational and Clinical Research Institute, Newcastle Upon Tyne, UK.
Objectives:
The evoked compound action potential threshold (ECAPT) provides an objective, quantifiable measure of dorsal column activation that reflects sensory fiber recruitment and aligns with the human perception threshold. This study characterized ECAPT variability in a rat model of neuropathic pain by comparing three estimation methods and evaluating associations with neuropathic condition, physiologic state, posture, pulse width (PW), recording direction, and recording distance.
Materials And Methods:
Adult male Sprague-Dawley rats with spared nerve injury-induced neuropathic pain (n = 17) and Sham controls (n = 8) were implanted with an epidural eight-contact lead spanning T11-L3. Input-output (IO) functions were recorded at 50 Hz using PWs of 20, 100, and 200 μs. ECAPT estimates were based on the first detectable ECAP response followed by three approaches: 1) no extrapolation of the first visually detectable ECAP response, 2) extrapolation to the zero-crossing of a smoothing spline fitted to the IO curve, and 3) extrapolation to the x-intercept of a linear regression applied to the initial rising phase of the IO curve.
Results:
ECAPT estimates varied across extrapolation methods, with spline- and regression-based approaches yielding lower estimates than visual detection without extrapolation. Shorter PWs required higher stimulation currents, whereas ECAPTs were generally lower under anesthesia than in awake animals. Posture-related variation was observed in an exploratory single-animal experiment. No consistent patterns in ECAPT estimates were identified with respect to neuropathic condition, recording direction, or recording distance. ECAP morphology and IO characteristics also varied with physiologic and technical conditions.
Conclusions:
ECAPT estimation is influenced by both the analysis approach and experimental conditions, particularly PW and physiologic state. Standardized threshold estimation and careful control of recording conditions are important for improving the reproducibility and interpretation of ECAP-derived measurements. ECAPT remains a promising metric for characterizing dorsal column activation and may support physiologically informed spinal cord stimulation dosing strategies.
