Target dependence of Nissl body ultrastructure in cat thoracic motoneurones

The effects on Nissl body (NB) ultrastructure of muscle reinnervation or neuroma formation were determined in cytochemically identified cat thoracic motoneurones subjected to axotomy by either nerve crush or nerve section with proximal ligation. Normal NB ultrastructure comprised highly ordered lamellae of rough endoplasmic reticulum (RER) with associated linear arrays of unbound polyribosomes. This ultrastructural orderliness was lost following axotomy, with or without light microscopic chromatolysis. While NBs were seen in the light microscope at late stages following both nerve crush or ligation, normal NB ultrastructure was only observed following nerve crush. An inductive effect of the periphery on NB ultrastructure is proposed and the implication of NB ultrastructure discussed in relation to protein synthesis.