Postmenopausal effects of intrastriatal estrogen on catalepsy and pallidal electroencephalogram in an animal model of Parkinson's disease

The main objective was to test the preventive and treatment effects of central injection of estrogen (ES) on muscular rigidity and pallidal EEG in menopausal rats' model of Parkinson's disease (PD). We hypothesized that intrastriatal pretreatment and post-lesion treatment by estrogen improve the pallidal local EEG and muscular stiffness in animal model of menopause with PD. Forty-eight female Wistar rats (300-350 g) were ovariectomized (OVX) and divided into two main groups: Non-pretreated subgroups; sham (S), lesioned (L), post-lesion treated (LT) and pretreated subgroups; pretreated (Pt), pretreated and then lesioned (PtL), pretreated and post-lesion treated (PtLT). Pallidal local EEG was recorded by a bipolar recording electrode and muscle stiffness was scored by Dekundy's test in freely moving rats. Muscle stiffness and pallidal local EEG were indicated as main outcome measures. In pretreated group the local pallidal EEG was decreased in sham-operated rats compared with non-pretreated group (P<0.01), and SNc lesioning decreased EEG in the non-pretreated (P<0.01), while it increased the EEG in the pretreated group (P<0.01). In both groups administration of ES restore the EEG to the respective sham-operated group (P<0.01). Regarding muscle stiffness, it increased after SNc lesioning in both pretreated and non-pretreated groups and ES administration decreased the rigidity significantly (P<0.05, P<0.001 respectively). However, the lesion-induced rigidity in pretreated groups was significantly less than non-pretreated groups (P<0.05). Because of its modulatory effect estrogen may protect dopaminergic neurons from injury and may interfere with the uptake of 6-hydroxydopamine (6-OHDA) into the nigral dopaminergic neurons or alter dopamine release and uptake in remaining neurons.