Ultrastructure of dorsal root projections in the toad spinal cord. An experimental neuroanatomical study following transection of dorsal root.

The distribution and the modalities of termination of the dorsal root afferents in the toad spinal cord have been investigated. The morphological changes of degenerating fibres and boutons at different survival times after root transection have been followed. Degenerating boutons were clearly identified due to the occurrence of both the dark and the filamentous types of degeneration similar to that described in cats. Most of the central endings of the primary afferents terminated in the dorsal horn of the spinal cord; however, degenerating boutons were also observed in the ventral horn region of the gray matter. The density of the degenerating elements located in the ventral gray was always lower than that observed in the dorsal horn. Dark and filamentous boutons which were present in the motoneuronal region, did not appear to be in synaptic contact with the soma of the motoneurons.