Retrograde changes in Clarke's column following neonatal hemicerebellectomy in the rat.

Long-Evans black-hooded rat pups underwent hemicerebellectomies at various postnatal ages. The animals were killed at 28 days of age and thoracolumbar segments of the spinal cord were removed and processed according to Golgi and Nissl techniques. Hemicerebellectomy at two and three days postnatally produced, in addition to cellular hypotrophy in Clarke's column, dendritic alterations which included a decrease in the number of primary dendrites and a reduction of the remaining dendrites to truncated stubs. Hemicerebellectomy at 21 days postnatally had little effect on either cell size or dendritic arborization. The role of the target nucleus in maintaining cell growth and dendritic arborization during critical developmental periods is discussed.