Gj. Sengstock et al., INFUSION OF IRON INTO THE RAT SUBSTANTIA-NIGRA - NIGRAL PATHOLOGY ANDDOSE-DEPENDENT LOSS OF STRIATAL DOPAMINERGIC MARKERS, Journal of neuroscience research, 35(1), 1993, pp. 67-82
Iron has recently been suggested to contribute to the pathogenesis of
Parkinson's disease (PD) because of the finding of increased iron leve
ls in the substantia nigra pars compacta (SNc) above those of control
patients. Iron is capable of catalyzing numerous reactions which could
lead to free radical formation and oxidative damage to DNA, proteins,
lipid membranes, and other biological molecules. Neurodegeneration in
the SNc of the PD brain may be a consequence of increased iron, which
promotes these cytotoxic reactions. To test whether excess iron could
play a causative role in the degeneration of nigral neurons, we infus
ed 1.25-6.3 nmol of iron into the rat substantia nigra (SN) unilateral
ly utilizing two different infusion protocols. All infusates were isos
motic and pH-balanced in a citrate-bicarbonate vehicle. Animals were d
ecapitated at either 1 or 2 months postinfusion. Striatal tissue was a
ssayed for biogenic amines by HPLC and the remaining brainstem was pro
cessed for histological analysis. Iron-stained coronal sections reveal
ed 1) no left/right staining difference with vehicle infusion, 2) a do
se-dependent iron accumulation in the infused SN that was restricted t
o the zona compacta and dorsal-most zona reticularis when the lowest i
ron concentration was infused, and 3) a dose-dependent reduction in SN
volume. Thionine-stained sections revealed neuronal loss and accompan
ying reactive gliosis within an area that corresponded closely to that
of increased iron staining. These degenerative changes were more exte
nsive in animals infused via a side-by side vs. a sequential protocol.
Neurochemically, there was a highly significant correlation between t
he amount of iron infused intranigrally and magnitude of reductions in
striatal DA, DOPAC, and HVA within the ipsilateral striatum. These da
ta indicate that iron infusion into the SN can cause degenerative chan
ges within the SN and that these changes can be restricted to the SNc
region when low amounts of iron are infused. The data further support
the hypothesis that iron-induced degeneration may contribute to the pa
thogenesis of PD.