Occurrence of the H reflex and the F wave in the rat.

In adult rats the tibial nerve was stimulated at the ankle and the evoked EMG of the foot muscles was recorded. A low threshold reflex discharge was elicited that was subsequently depressed by stronger stimuli eliciting the direct (M) wave. This discharge was abolished by cutting the dorsal roots (except for 1-3% postulated to be due to recurrent discharge). It had a central latency of about 2 msec, was depressed by stimulation rates above 0.3/sec and showed posttetanic depression, all of which are also properties of the rats's monosynaptic reflex. By analogy it is assumed to be an H reflex.