Caudal end of the rat spinal dorsal horn.

We have previously demonstrated that the transformation of the caudal spinal cord through the conus medullaris to the filum terminale takes place in three steps. In the conus medullaris the twin layers of CGRP-immunoreactive and IB4-labeled primary afferent fibers as well as the translucent portion of the superficial dorsal horn equivalent to the substantia gelatinosa discontinue before the complete removal of the dorsal horn. Parallel with these changes VGLUT1-immunoreactive myelinated primary afferent fibers arborize not only in the deep layers but also in the entire extension of the remaining dorsal horn, while scattered CGRP fibers still remains at the margin of and deep in the dorsal horn.

Neurochemical architecture of the filum terminale in the rat.

Contrary to the widespread assumption, the filum terminale in the rat possesses a precise glial and neuronal organization. The processes of glial fibrillary acidic protein-stained astrocytes form a rich, three dimensional array. The crescent shaped white matter could be outlined with antibody detecting oligodendrocytes.

The caudal end of the rat spinal cord: transformation to and ultrastructure of the filum terminale.

Contrary to the current belief, the spinal cord of the rat does not terminate with the conus terminalis (CT), but its basic components (central canal, gray matter, white matter) continue in the filum terminale (FT). Proceeding caudally in the conus terminalis, first the motoneuron cell column discontinues in the ventral horn. More caudally the dorsal horns separate from the intermediate zone, and discontinue.