Fig. 10. Effects of spikes from the lump receptor on the synaptic connection between the fast extensor tibiae motor neuron (FETi) and flexor motor neurons. (A) The experimental protocol. Antidromic spikes were evoked in FETi by stimulation of the extensor muscle. 5 stimuli at intervals of 1 s were given before the flexor tendon was pulled. 4 s after the last stimulus the tendon was pulled and 5 more stimuli were delivered. The motor neuron was hyperpolarized by the sensory spikes and the EPSPs were reduced in amplitude. Repetition of the electrical stimuli after the movement of the tendon showed that the EPSPs recovered to their previous amplitude. (B) Comparison of the second EPSP before the sensory stimulus with the second EPSP during the sensory spikes (grey trace) shows the changes in amplitude.