The role of axonal transport in the regulation of enzyme activity in sympathetic ganglia of adult rats

The relationship of perikaryal and presynaptic enzyme activity to axonal transport was studied in adult sympathetic neurons in the rat superior cervical ganglion (SCG). Surgical axotomy or local colchicine application to the postganglionic nerves resulted in a significant decrease in ganglionic tyrosine hydroxylase (T-OH) activity without a significant alteration in choline acetyltransferase activity. Colchicine did not appear to block axonal impulse conduction since pupillary and eyelid function remained normal. Consequently, the reduced T-OH activity resulted from alteration of other axonal functions. Axotomy or colchicine application decreased T-OH activity in decentralized ganglia, suggesting that the depression of perikaryal T-OH was not secondary to altered orthograde transsynaptic interactions. Colchicine did not prevent transsynaptic induction of T-OH by reserpine, suggesting that axonal transport is not necessary for enzyme induction. Nerve growth factor (NGF) treatment partially prevented the effects of colchicine application. It is concluded that in adult sympathetic neurons both orthograde transsynaptic mechanisms and the retrograde transport of NGF normally govern perikaryal T-OH activity.