Distribution of zinc in the substantia nigra of rats treated with 6-hydroxydopamine

To study the relationship between tissue accumulation of Zinc (Zn) and neurodegeneration in the nigrostriatal dopaminergic pathway,⁶⁵Zn distribution in this pathway was examined after unilateral injection of 6-hydroxydopamine (6-OHDA) into the substantia nigra of rats. When⁶⁵ZnCl₂ was intravenously injected 4 days after treatment with 6-OHDA,⁶⁵Zn was concentrated in the ipsilateral substantia nigra 6 days after⁶⁵Zn injection. On the other hand, 19 d after treatment with 6-OHDA,⁶⁵Zn distribution in the ipsilateral substantia nigra was decreased to the level of the contralateral one. When NH₄ ⁹⁹TcO₄, which cannot go through the blood-brain barrier, was injected into rats 4 d after treatment with 6-OHDA,⁹⁹Tc was concentrated in the ipsilateral substantia nigra 30 min after⁹⁹Tc injection, but no longer detectable 6 d after injection. These results suggest that Zn is necessary for a repair process called replacement gliosis after the death of neurons and that excess Zn does not accumulate in the lesion after completion of the gliosis.