Fig. 4

Representative response of Renshaw cells in the ventral horn. a Orthodromic activation following stimulation of the L1 nerve (L1 abdominal medial and lateral branches). The intensity of electrical stimulation was gradually increased from threshold (T) to T × 2.11. Each panel reflects the results of five superimposed traces. Open squares, filled diamonds, and filled squares represent the first, second, and third spikes, respectively. Arrows indicate the time of stimulation. b Synaptic excitation following stimulation of the L1 nerve. Arrows indicate the time of stimulation. c Relationship among stimulus voltage, latency of the activated spikes, and the amplitude of the field potentials. The ordinate indicates the amplitude of the field potential (left) and the latency of the activated spikes (right). Open squares represent the antidromic field potential. Filled squares represent the latency of the antidromic spikes. The abscissa indicates the intensity of the stimulation multiplied by the threshold of the stimulus voltage. d Convergence of excitatory inputs from other spinal segments. L2 medial: L2 medial branch. L2 lateral: L2 lateral branch. The T13, L1, and L3 nerves were stimulated. Note that Renshaw cells were activated only when the L1 nerve was stimulated. e Cross-sectional schematics of the spinal cord at the representative L1 spinal segment. The open square indicates the abdominal motor nucleus. The filled circle represents the Renshaw cell recording sites. Open circles represent the recording sites that projected to the lumber transverse section. Roman numerals indicate the Rexed laminae. IL nucleus intermedio-lateralis; CC Clarke’s column. f Recording sites of Renshaw cells. Cross-section of the spinal cord at the L1 spinal segment. White arrow represents recording sites marked with Fast Green FCF dye