Action of 6‐hydroxydopamine on lamb sympathetic ganglia, vas deferens and adrenal medulla: a combined histochemical, ultrastructural and biochemical comparison with the effects of reserpine

The effects of a single dose of 6‐hydroxydopamine (6‐OHDA) compared with those of chronic reserpine treatment were studied in lamb sympathetic neurones and adrenal medulla by a combination of fluorescence histochemistry, electron microscopy and radiochemical assay. In sympathetic ganglia, 6‐OHDA produced a rise in noradrenaline concentration within 24 h, and falls in tyrosine hydroxylase and monoamine oxidase activities, whereas reserpine caused a fall in noradrenaline, a rise in tyrosine hydroxylase activity and no change in monoamine oxidase activity. The fluorescence of intra‐ and postganglionic axons increased greatly within 24 h of 6‐OHDA, and there was a corresponding accumulation of large dense‐core vesicles within many axons whose neurotubules were disrupted. The changes were almost reversed after 3 weeks. In the vas deferens, the concentration of noradrenaline and tyrosine hydroxylase and monoamine oxidase activities had all fallen 24 h after 6‐OHDA treatment and had started to recover 3 weeks later. In the adrenal medulla, 6‐OHDA did not alter NA concentrations but increased tyrosine hydroxylase activity whereas reserpine depleted noradrenaline and increased tyrosine hydroxylase activity. The changes produced in sympathetic ganglia by 6‐OHDA may be due both to a direct action on the axoplasmic transport of noradrenaline containing vesicles and indirectly to the reaction of the neurones to loss of the integrity of their axons. 1971 British Pharmacological Society