Neuroprotective effects of phenylethanoid glycosides from Cistanches salsa against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)induced dopaminergic toxicity in C57 mice

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) has been employed to create a Parkinson's disease-like model in both rodents and primates based primarily on its ability to create a striatal dopamine deficit due to the loss of dopaminergic neurons in the substantia nigra compacta. The present study was carried out to determine the possible effects of phenylethanoid glycosides (PhGs) from Cistanches salsa (C. A. MEY, G. BECK) on attenuating the serious behavioral disorder and increasing dopamine (DA) levels in the striata of MPTP-lesioned C57 mice. MPTP (30 mg/kg i.p. for 4 d) induced serious behavioral disorders and significantly reduced striatal DA levels in C57 mice. In spontaneous motor activity and rotarod tests, obvious behavioral differences were seen between control and model groups. PhGs (10, 50 mg/kg) significantly increased the spontaneous movement number and latent period of mice on the rotating rod (p<0.01). Injections of MPTP 30 mg/kg for 4 d caused a significant reduction in DA, 3,4-dihydroxyphenyl acetic acid, and homovanillic acid in striata analyzed by HPLC-electrochemistry (p<0.01). The neurotoxic effects of MPTP were attenuated by pretreatment with PhGs (10, 50 mg/kg) in a dose-dependent fashion. The apparent neuroprotective effects of PhGs on nigral dopaminergic neurons were also confirmed by the results of immunohistochemical staining. The present in vivo data clearly demonstrate that PhGs can protect dopaminergic neurons against dopamine neurotoxicity induced by MPTP, as suggested by an earlier in vitro study. The neuroprotective effects of PhGs were the first reported for a natural product.