Induction of fos expression by activity in the spinal rhythm generator for scratching

Fos expression was evaluated immunohistochemically in L7-S1 spinal segments after inducing fictive scratching in paralysed, unanaesthetized, decerebrate cats. The activity was induced by cutaneous stimulation of the pinna on one side and recorded from peripheral nerves. A cumulative duration of scratching of 60 to 90 min was effective in inducing fos expression. Most Fos-positive neurones were found in the dorsolateral part of the ventral horn and in the intermediate region of the spinal cord on the scratching side. In sham-operated animals the finding of Fos-positive neurones in these areas was very rare.