Fig. 1

Experimental arrangement. Intracellular recordings were obtained from abdominal motoneurons with intact dorsal roots in order to identify antidromic spikes and Ia-EPSPs. Afferent volleys arriving at the dorsal-root entry zone were recorded using silver ball electrodes. The dorsal roots were cut in order to record R-IPSPs from abdominal motoneurons. Extracellular spikes were recorded from single Renshaw cells. T thoracic, L lumbar, br branch, EO m external oblique muscle, Stim stimulation, Ia-EPSP excitatory postsynaptic potential of Ia fibers, R-IPSP recurrent inhibitory postsynaptic potential