H-reflex waveform and latency variability in rats.
The right tibial nerve of each of 11 anesthetized male Fischer 344 rats was electrically stimulated at the ankle, and H-reflexes were recorded simultaneously from four locations in the hind foot. Needle electrodes were used for stimulating and recording. The mean (+/- SD) latency to the dominant peak of the H reflex was 10.21 +/- 0.75 msec. Individual rats had a 10% difference in latency from the "fastest" to the "slowest" locations in the foot, although any of the four locations could produce the fastest (shortest latency) response. The H reflexes varied from simple, single peak waveforms to complex multiple peak waveforms. The dominant peak polarity was unpredictably either positive or negative. These variations in complexity and latency occurred among rats and among the four locations within an individual rat. The dominant peak was identified in complex waveforms by adjusting the stimulating intensity and by recording from more than one location in the foot. The smallest coefficient of variation (5.57%) resulted from selecting data from the fastest electrode locations.