Aggravation of 6-hydroxydopamine-induced dopaminergic lesions in metallothionein-I and -II knock-out mouse brain.

The effects of two major isoforms of metallothioneins (MTs), MT-I and -II, on dopaminergic neurotoxicity of 6-hydroxydopamine (6-OHDA) were examined using intracerebroventricularly 6-OHDA-injected MT-I, II knock-out (KO) mice. The loss of dopamine neurons in the substantia nigra pars compacta induced by the 6-OHDA injection was significantly aggravated in the MT-I, II KO mice, compared with that in the 6-OHDA-injected wild-type mice. The present results, taken together with the antioxidant properties of MT-I and -II suggest that MT-I and -II exert neuroprotective effects against the dopaminergic neurotoxicity of 6-OHDA at the nigral cell body by scavenging free radicals.