Recuperative effect of estrogen on rotenone-induced experimental model of Parkinson's disease in rats

Parkinson's disease (PD) is described as the loss of dopaminergic neurons located in the substantia nigra (SN) region of the brain and a progressive motor failure. Increased frequency of PD in women, especially after menopause, suggests the effect of estrogen. This view has been supported with empirical studies. Therefore, the effect of estrogen in an experimental model of Parkinson's disease induced by rotenone was investigated. A total of 32 female Wistar Albino rats were randomly assigned to four groups (control group, ovariectomy group, Parkinson's group, Parkinson's + estrogen group). The Parkinson's group received rotenone subcutanously at the dose of 2.5 mg/kg bw, on the 1st, 2nd, 3rd 4th, 6th, 9th, 12th, 15th, 18th, and 21st days animals in the Parkinson's + estrogen group received retonon as in the Parkinson's group and was additionally subcutaneously given estrogen (implant containing 0.5 mg 17 β-estradiol lasting for 21 days). The rats were subjected to rotarod, pole, and swimming tests at the end of the experiment for comparison of their motor activities, and then, histopathological and biochemical analyses were performed on the tissues that were extracted. The rotarod results revealed that Parkinson's group had the shortest time (32.33 ± 3.98 sn) than the groups of control (92.50 ± 12.60 s) ovariectomy (71.42 ± 10.58 s), and Parkinson's + estrogen (71.37 ± 9.26 s). The results of pole disclosed that return and landing time prolonged for Parkinson's group when compared with other groups (return time for control 2.98 ± 0.38 s, ovariectomy 3.02 ± 0.75 s, Parkinson 5.91 ± 0.33 s, Parkinson's + estrogen 3.48 ± 0.42 s and landing time for control 5.30 ± 0.59 s, ovariectomy 5.45 ± 0.73 s, Parkinson 9.80 ± 0.90 s, Parkinson's + estrogen 5.37 ± 1.02 s). Parkinson's group had longest (90.71 ± 12.56 s) swimming time to reach the target when compared with control (33.16 ± 8.68 s), ovariectomy (47.37 ± 12.19 s), and Parkinson's + estrogen (49.82 ± 5.78 s). Histopathological examination indicated a significant difference in tyrosine hydroxylase-stained cells (dopaminergic neurons and dopamine) between the Parkinson's + estrogen group and the Parkinson's group. The biochemical analyses of Caspas-3 activation in SN and striatum (STR) was significantly different between the Parkinson's + estrogen group and the Parkinson's group, but this difference was not observed in STR while evaluating Bcl-2. The results of this study suggested that estrogen may have a recuperative effect on PD.