CHANGES OF ENZYME PATTERN IN THE SYMPATHETIC NERVOUS SYSTEM OF ADULT MICE AFTER SUBMAXILLARY GLAND REMOVAL; RESPONSE TO EXOGENOUS NERVE GROWTH FACTOR

—Removal of the submaxillary glands, the apparent site of NGF synthesis in adult mice, caused a decrease in the activity of all the enzymes involved in the biosynthesis of noradrenaline in the peripheral sympathetic nervous system. Thus, tyrosine hydroxylase (phenylalanine 4-monooxygenase, EC 1.14.16.1) DOPA decarboxylase (EC 4.1.1.28.) and dopamine β-hydroxylase (EC 1.14.17.1.) showed reduced activity 10 days after removal of the submaxillary glands in both superior cervical and stellate ganglia. This decrease in enzyme activity persisted up to 100 days after surgery. The fourth enzyme studied, choline acetyl-transferase (EC 2.3.1.6.) which is exclusively localized within the presynaptic cholinergic terminals of the ganglia was not affected by sialectomy. A dose of 50 μg NGF/animal/day given over 4 days was only able to restore the enzyme activity to control levels in the superior cervical ganglia of sialectomized mice whereas in stellate ganglia the enzyme activities rose above control levels to a similar extent in sialectomized and non-sialectomized animals. These results provide biochemical evidence that NGF may play a role not only during the growth and normal development of the peripheral sympathetic nervous system but also in the maintenance of its functional integrity in the adult animal.