[Variations in the membrane potentials of motor neurons during the generation of scratching]

The activity of motoneurons of the ankle flexor and extensor muscles was recorded intracellularly during fictitious scratching in decerebrate curarized cats. Before the beginning of rhythmical oscillation a large depolarization and tonic discharge were observed in flexor motoneurons, while the membrane potential of extensor ones did not change. When the rhythmical generation began, a short periodic hyperpolarization and corresponding pause in the discharge lasting for the extensor phase of the cycle appeared in flexor motoneurons. In extensor motoneurons a periodic depolarization increasing in the course of the flexor phase was observed; a maximal depolarization occurred in the extensor phase in which a short burst of spikes was generated.