[Activity of propriospinal neurons in cats during the scratch reflex]

In the thalamic cats immobilized with flaxedil, the tactile stimulation of the pinna evoked fictitious scratching, i.e. rhythmical activity of the hindlimb motoneurons with a pattern of discharge typical of the actual scratching. Activity of propriospinal neurons from the segments C1--C2 and Th4--Th7 was recorded during such scratching. The neurons were identified by the antidromic response to L1 stimulation. Most neurons did not respond to the pinna stimulation, but some neurons did. They were tonically active during fictitious scratching. The neurons from cervical segments responded also to some other peripheral stimuli, but neurons from thoracic segments did not. Their activity could be inhibited by stimulation of the contralateral pinna. A role of propriospinal neurons in the activation of the spinal mechanisms of scratching is discussed.