Early rapid and transient increase in ornithine decarboxylase activity within sympathetic neurons after axonal injury.

The activity of ornithine decarboxylase (ODC) was examined in the rat superior cervical ganglion during development and after postganglionic axotomy. During development the enzyme activity in the ganglion was transiently elevated at 19 days gestation (2 days before birth) and then declined to low adult activities by 5 days after birth. After axotomy the enzyme activity in the ganglion was rapidly increased. As early as 2 h after the injury the activity was increased to 200% and by 10 h it attained a peak of 453% above control values. The activity then rapidly declined to a lower value of about 200% above control by 24 h, where it remained as long as 5 days and then returned to control values by 10 days postoperative. The early increase in ODC activity was demonstrated by inhibitor cytochemistry to occur within neuronal cell bodies. The ODC activity was also increased after preganglionic nerve transection (denervation) (275%), end organ removal (60%), and 6-hydroxydopamine treatment (75%). We conclude that increased ODC activity is one of the earliest events in the reaction of the nerve cell body to axonal injury, and that increased ODC activity is a common feature of drastic metabolic alterations in neurons of the superior cervical ganglion.