Descending projections to coccygeal spinal segments in the cat.

The descending projections to coccygeal spinal segments influencing tail movement were studied by retrograde wheat germ agglutinin-horseradish peroxidase (WGA-HRP) tracing methods in 12 cats. WGA-HRP solution was injected into the 3rd and 4th coccygeal segments and hemisection of the right side of the spinal cord was performed at the 3rd sacral-1st coccygeal segmental level. Labelled propriospinal neurons were distributed in laminae III-VIII and X of the spinal cord between the cervical and lumbosacral spinal segments, predominantly on the left. The greatest density of labelled cells as in the lumbar enlargement. In the brainstem a high density of labelled cells was observed mainly in the lateral vestibular, gigantocellular reticular and magnocellular reticular nuclei on the left side, and the nucleus raphe magnus, pallidus and obscurus. These findings indicate significant descending projections to the coccygeal spinal cord in the cat which could be responsible for tail movements in the cat.