EVIDENCE THAT 6-HYDROXYDOPAMINE DECREASES SYNTHESIS OF DOPAMINE--HYDROXYLASE IN SYMPATHETIC GANGLIA

¹ Department of Pharmacology, Mayo Medical School, Rochester, Minnesota

Administration of 6-hydroxydopamine (200 mg/kg i.v.) led to a decrease in the activity of dopamine--hydroxylase (DBH) in sympathetic ganglia of the rat. In superior cervical ganglia, this decrease was not prevented by prior administration of reserpine (2 mg/kg s.c.). The effects of 6-OH-dopamine on the subcellular distribution of DBH in stellate ganglia were: 1) an initial but transient decrease in soluble DBH activity and 2) a later parallel decline in both soluble and particulate DBH activity. Measurements of the accumulation of DBH activity above a ligature on the sciatic nerve indicated that 6-OH-dopamine administration led to transport at normal velocities of smaller than normal amounts of DBH. Turnover experiments in stellate ganglia revealed a dramatic reduction of the apparent rate of synthesis of DBH that coincided with the time when enzyme activity first began to fall rapidly. On the other hand, 6-OH-dopamine had no effect on incorporation of ³H-leucine into HClO₄-insoluble material and led to a slight but significant increase in protein content in stellate ganglia.

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