[Excitatory postsynaptic potentials in the lumbar motor neurons of frogs induced by stimulation of muscle and cutaneous nerves].

The postsynaptic effects evoked in lumbar motoneurons by stimulation of different muscle and cutaneous nerves of hindlimbs were studied by means of intracellular recording in the frog isolated spinal cord. The data obtained confirm presence of monosynaptic connections between primary afferents and spinal motoneurons. Monosynaptic EPSPs were shown to be due to low threshold muscle afferent volleys in homonymous nerves and did not generate spike discharges. The mean amplitude of monosynaptic EPSPs was 1.1 +/- 0.12 mV, time-to-peak 1.76 +/- 0.16 msec, time constant of decay from 6.0 to 15.0 msec. EPSPs with no synaptic delay were recorded in some motoneurons which suggest existence of an electrical mechanism of transmission.