Fulminant Purkinje cell death following axotomy and its use for analysis of the dendritic arborization

Young and adult cats were operated upon and a number of the vermal cerebellar folia were either transected with a vertical incision or isolated by a horizontal cut. In the proximity of the lesion, Purkinje cell bodies and their dendritic trees became stainable with the Fink-Heimer method. Electron microscopy of the silver stained sections show that the argyrophilic Purkinje neurons undergo an electron dense type of degeneration. Stellate cell dendrites adjacent to the degenerating Purkinje trees are normal, suggesting that the cause of cell death is axotomy close to the perikaryon rather than direct injury. The retrograde Purkinje cell degeneration is fulminant since it is evident 6 hours after the lesion. In Fink-Heimer stained sections the entire dendritic tree is impregnated 1-3 days after the lesion. 4-10 days post-operatively, the flattened dendritic tree becomes fragmented and is partially phagocytized. The silver stained arborizations are approximately 280 mu in width and have an uneven thickness (8-16 mu). In longitudinal and horizontal silver stained sections of lesioned cerebellar folia, uninterrupted fields of degenerating Purkinje cell arborizations can be seen, suggesting that the arborizations overlap. The overlap was demonstrated in electron micrographs of single degenerating arborizations surrounded by normal dendritic trees. The degree of overlap varies with the thickness of the arborization and is in the order of 1-2 mu. This approach indicates that each Purkinje tree occupies an exclusive sheet of molecular layer 8 mu thick and may overlap for as much as 2 mu on each side with neighboring trees. The average thickness of the Purkinje tree is approximately 12 mu.