Fig. 2

Representative response of RLCs and intracellular recording from PMNs. a The antidromic field potential of pudendal MNs (left) and discharges of RLCs in S1 spinal level, which were excited by stimulation of the pudendal nerve (right). Discharge was recorded while gradually increasing the strength of stimulation to 2.17 × threshold in this case. The arrow indicates stimulus artifact. b A typical relationship among stimulus intensity, number and latency of the activated spikes, and amplitude of the field potentials. The circle represents the amplitude of antidromic field potential. The square indicates the number of activated spikes. The triangle indicates latency of the first spikes of RLCs. The abscissa indicates the intensity of stimulation multiplied by threshold of the stimulus voltage. The firing frequency of RLCs gradually increased and latency of first spike of RCs gradually decreased according to stimulation intensity, reaching plateaus at intensities sub-maximal of antidromic volley (1.3 × of threshold in this case). c Convergence of excitatory input from other pudendal nerves. The EAS nerve, EUS nerve, and perineal nerves were stimulated. Note that the RLC was activated only when EAS nerve was stimulated. All waves were superimposed 10 to 15 times. The arrow indicates stimulus artifact. The asterisk indicates antidoromic field potential of the PMNs. d Synthetograph of each RLC, showing the anatomical relationship between Onuf’s nucleus (dotted circle) and RLCs. The circle represents the recording site of RLCs activated by stimulation of the pudendal nerve; the square indicates that by the EAS nerve; and the triangle indicates that by the EUS nerve. e Intracellular recording from EAS motoneurons (following the stimulation of the EAS nerve, at intensities just below the threshold for activation of antidromic spikes in the impaled EAS motoneurons). Although membrane potentials were summed over 200 times, synaptic potentials were not observed. The arrow indicates stimulus artifact. The asterisk indicates antidoromic field potential of the PMNs. The gray trace indicates extracellular recording and the black trace indicates intracellular recording