An ultrastructural and histochemical study of the short‐term effects of 6‐hydroxydopamine on adrenergic nerves in the domestic fowl

The effects of 6-hydroxydopamine (6-OHDA) on adrenergic nerves in the domestic fowl have been investigated with ultrastructural and fluorescence histochemical methods.2. 6-OHDA depletes the nerves of catecholamine, initially by displacing it from the storage vesicles. 6-OHDA enters large as well as small vesicles, indicating that large granular vesicles in adrenergic nerves are sites of amine storage.3. Doses of 6-OHDA, insufficient to cause degeneration, still cause loading of the vesicles.4. The effects of various drugs on the action of 6-OHDA indicate that this drug must be taken up by the nerves and reach a critical extragranular axoplasmic concentration before degeneration will occur; 6-OHDA bound in the vesicles plays no part in the degenerative process.