Experimental studies on permeability of tracers into the spinal cord

For investigation of the intramedullary penetration of metrizamide, the intramedullary movements of fluorescein, Evans Blue, Horseradish peroxidase (HRP) and ionic lanthanum in the normal cord and experimental syringomyelia of rats were studied. Syringomyelia was induced by injection of kaolin suspension into the cisterna magna. Subsequently HRP or ionic lanthanum was perfused into the subarachnoid space and its distribution was examined by electron microscopy. In normal rats, HRP mainly became localised in the basement membrane between the pia mater and glial cells and only a few vesicles migrated into the extracellular spaces (ECS) between glial cells. Ionic lanthanum, however, migrated deep into the ECS. In rats with experimental syringomyelia many vesicles of HRP migrated deep into the ECS of glial cells and the white matter. These findings indicated that the ECS of the marginal glia and the neuropil constitute part of a pathway through which metrizamide migrates into the intramedullary cavity.