Related Experiment Video
Updated: Apr 19, 2026
Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat
Published on: April 18, 2020
Standardization of a Supramaximal Stimulation Protocol for Electrophysiological Assessment of the Intact Rat Median
Tiago Bastos Taboada1,2, Fernanda Marques Pestana1, Julia Teixeira Oliveira1
1Laboratory of Neurodegeneration and Repair, Department of Pathological Anatomy, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil, ufrj.br.
Introduction:
Electroneuromyography (ENMG) is the gold-standard method for assessing peripheral nerve function through compound muscle action potential (CMAP) amplitude and latency. However, methodological heterogeneity across studies limits reproducibility and comparability, particularly regarding stimulation intensity and electrode configuration.
Objective:
This study is aimed at standardizing an ENMG protocol for the intact median nerve in rats by defining the minimal supramaximal stimulation intensity required to evoke maximal CMAP amplitude with stable latency.
Methods:
A total of 10 adult male Wistar rats (250-300 g) were anesthetized with ketamine and xylazine. The right median nerve was surgically exposed at the brachial plexus level. A bipolar hook electrode delivered square-wave pulses (0.1 ms, 1 Hz) at descending intensities (20-0.1 V), with a 60-s interval between intensity blocks. CMAPs were recorded from the flexor digitorum superficialis using monopolar needle electrodes. Signals were amplified (10 Hz-10 kHz band-pass) and digitized at 20 kHz. Amplitude and latency were analyzed across intensities to determine the supramaximal plateau.
Results:
CMAP amplitude reached a plateau between 20 and 10 V, indicating full motor unit recruitment. Below 10 V, amplitude decreased progressively, and no response was observed at 0.1 V. Latency remained stable within the supramaximal range and increased only near threshold intensities.
Conclusion:
This study establishes a standardized supramaximal stimulation parameter (10 V) for electrophysiological assessment of the intact rat median nerve. Defining this reference intensity enhances methodological consistency and supports reproducibility in experimental models of peripheral nerve research.
