The Protective Effect of Vitamin E on Locus Coeruleus in Early Model of Parkinson's Disease in Rat: Immunoreactivity Evidence

Background: Free radical formation and oxidative stress might play an important role in the pathogenesis of Parkinson's disease (PD). In vitro data indicate that neuromelanin (NM) pigment is formed the excess cytosolic catecholamine that is not accumulated into synaptic vesicles via the vesicular monoamine transporter 2 (VMAT2). We designed this study to investigate the neuroprotective effects of vitamin E in the early model of PD. Methods: Male rats (n = 40) with unbiased rotational behavior were randomly divided into five groups: sham operated group (SH, n = 8), vehicle-treated SH group (SH + V, n = 8), vitamin E-treated SH group (SH + E, n = 8), vehicle-treated lesion group (L + V, n = 8) and vitamin E-treated lesion group (L + E, n = 8). Unilateral intrastriatal 6-hydroxydopamine (12.5 µl) lesioned rats were treated intramuscularly with α-tocopherol acid succinate (24 I.U/kg, intramuscular [i.m.]) 1 h before surgery and three times per week for 2 month post-surgery. To evaluate the vitamin E pretreatment efficacy, tyrosine hydroxylase (TH) immunoreactivity and immunostaining intensity (ISI) for monoamine transporter 2 were used. Results: THimmunohistochemical analyses showed a reduction of 20% in locus coeruleus (LC) cell number of vitamin E pretreated lesioned group but the cell number dropped to 60% in the lesioned group. The ISI of the cells was measured for VMAT2 in LC. Lesioned groups: 1) had the lowest VMAT2 ISI of all neurons 2) There was an inverse relationship between VMAT2 ISI and NM pigment in the locus and 3) Neurons with the highest VMAT2 ISI also had high TH ISI. Conclusion: The data support the hypothesis that repeated i.m. administration of vitamin E exerts a protective effect on the LC neurons in the early model of PD.