[Activity of interneurons of the lumbosacral division of the spinal cord during fictive scratching]

Impulse activity of lumbosacral interneurons was recorded extracellularly during fictitious scratching in decerebrated immobilized cats. Most neurons whose activity was modulated during fictitious scratching were revealed in the lateral intermediate zone and in the lateral ventral horn. These neurons were divided into some groups differing in the type of activity modulation during fictitious scratching. Neurons whose activity did not change during fictitious scratching were mainly located dorsally in the gray matter. Cells showing wide convergence of excitatory influences from high threshold cutaneous and muscle afferents referred mainly to "aiming" neurons. In contrast to "aiming" neurons, most cells with inputs from only low threshold cutaneous or high threshold muscle afferents belonged to "scratching" neurons. The neuronal activity in different groups is shown to depend on the limb position. The neuronal organization of the spinal scratching generator is discussed on the basis of the obtained data.