Neurally mediated increase in dopamine-beta-hydroxylase activity.

The development of a sensitive and specific enzymatic assay for dopamine-beta-hydroxylase has enabled us to measure the activity of this enzyme in several tissues where it has previously been measured. The administration of reserpine leads to an increase in dopamine-beta-hydroxylase activity in the rat adrenal, heart, salivary gland, and in sympathetic ganglia. The increase in the heart is preceded by a small but significant fall. We have confirmed the increase in tyrosine hydroxylase which follows the administration of reserpine and have found that the activity of phenylethanolamine-N-methyltransferase also increases after administration of this drug. The activities of two enzymes not involved in the synthesis of catecholamines, monoamine oxidase and lactate dehydrogenase, are not affected by reserpine treatment. The rise of dopamine-beta-hydroxylase activity in the sympathetic ganglia is blocked by surgical decentralization.