Long-term persistence of GAD activity in injured crayfish CNS tissue.

Crayfish CNS fibers were isolated in vivo from their cell bodies, from cellular connections in the CNS, and from peripheral sensory and effector cells. The glutamic acid decarboxylase (GAD) activity of the experimental tissues was about half of that of the sham-operated and unoperated control tissues by two weeks after surgery and remained at about that level during the ensuing six weeks. During that time, there was no significant behavioral, electrophysiological, or histological evidence of regeneration of nerve fibers across the lesion sites. The crush-isolated connectives possessed many intact axon profiles and non-neuronal cell nuclei. The long-term persistence of GAD activity in the injured CNS tissue may reflect the involvement of glial cells in maintaining neurotransmitter levels.