Retrograde changes in transglutaminase activity after peripheral nerve injuries

It has been previously demonstrated that transglutaminase activity in rat superior cervical ganglion is rapidly and transiently increased minutes after nerve injury. The present series of experiments sought to determine: (1) whether or not similar changes are expressed by other peripheral neuronal systems, and (2) if injury-induced changes in the enzyme activity can be detected along the injured nerve, and if so do they occur in axons or in non-neuronal cells. In the nodose ganglion transglutaminase activity increased (∼40%) 48 h after the vagus nerve was crushed 25 mm from the ganglion. In the vagus nerve the activity was transiently increased (∼100%) within 1 h, followed by a second increase (∼140%) after 3 h. This occurred only in the proximal nerve stump close to the injury site and not in the section of nerve closer to the ganglion. Comparable enzyme activity was found in unoperated vagus nerve and in distal stumps of previously ligated vagus nerves. In dorsal root ganglia no changes were found for up to 24 h after the sciatic nerve was crushed 40 mm from the ganglion. In the facial nucleus a transient increase was observed after the facial nerve was crushed about 14 mm distally with a peak (∼300) at 3 days and a decline within 14 days. A second lesion of the facial nerve made 12 days following a conditioning lesion led to a rebound of enzyme activity in the facial nucleus. We conclude: (1) early changes in transglutaminase activity may be induced in nerves or ganglia at close proximity to the nerve injury site; (2) in the injured nerve the enzyme activity is probably associated with non-neuronal elements; (3) after nerve injury late changes may occur retrogradely in the region containing parent nerve cell bodies, either in the neurons or perhaps in reactive glial cells.