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. 2018 May 1;35(9):1057–1068. doi: 10.1089/neu.2017.5297

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Copyright 2018, Mary Ann Liebert, Inc.

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FIG. 2. — Assessment of activation threshold changes after 4-AP or 4-AP-3-MeOH application in injured spinal cord. (A) Spinal cord ventral white matter segments were stimulated with intensities ranging from 1.85 to 6.5 V, and the responding compound action potential (CAP) waveforms were superimposed to demonstrate the amplitude changes in both pre-drug and post-treatment (4-AP or 4-AP-3-MeOH) conditions. (B,C) Plots show normalized CAP responses (% of max CAP amplitude pre-drug) of injured spinal tissue at each stimuli intensity. Note a significant increase in CAP amplitude from pre-drug to 100 μM of 4-AP (N = 10; B) or 100 μM of 4-AP-3-MeOH (N = 5; C) application at stronger stimuli intensities. (D,E) Plots show the relationship between normalized CAP amplitudes of pre-drug and after the treatment of 4-AP or 4-AP-3-MeOH. Specifically, normalized CAP responses (as % of max CAP amplitude) of injured spinal cord before and after treatment of 4-AP (D) or 4-AP-3-MeOH (E) are plotted at the same stimulus intensities. The relative linear relations suggest minimal changes in activation threshold after either 4-AP or 4-AP-3-MeOH application to injured spinal cord segment ex vivo. This also indicates little difference in the susceptibility of axons with small or large caliber to the 4-AP- or 4-AP-3-MeOH-mediated conduction restoration. 4-AP, 4-aminopyridine; 4-AP-3-MeOH, 4-aminopyridine-3-methanol.