| Parkinson's disease(PD) is a chronic neurodegenerative disease of nervous system, which is mainly characterized by a progressive degeneration and necrosis of dopaminergic(DAergic) neurons in substantia nigra(SN), as well as the decrease of dopamine(DA) content in striatum. The theory on the oxidative stress-free radicals play a very important role in the death of DAergic neurons in PD, and anti-oxidant therapy is currently regarded as an effective strategy to halt the progression of PD. Therefore, it is clinically significant to explore the effective anti-oxidant drug with mild toxicity.Scorpion venom (SV) is a complex mixture constituted of polypeptides that exhibiting different pharmacological activities. Our previous work found that SV had the effect of clearing out of the oxygen-derived free radicals by in vitro experiments. In addition, SV resisted to the toxicity of excitatory amino acid. Whereas, oxidative stress and excitative neurotoxicity are both involved in the progression of PD. This indicates that SV possibly possesses the therapeutic effect on PD. In this study, the protective effect of SV on DAergic in SN was investigated by the PD model mice treated with l-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP).Meanwhile, the cytomolecular mechanism of SV on therapeutic was also studied.C57BL/6 mice were injected with MPTP( 20mg/kg/day,i.s.c.)for 8 days to establish PD model. Two doses of SV (20mg/kg and 200mg/kg) were respectively given for 2 weeks in the treatment groups. Amimals were examined behaviorally with the pole test, traction test and the swimming test consecutively. The brains were then removed immediately and the striatum were dissected out. Contents of DA and homovanillic acid(HVA) were measured by high-performance liquid chromatography with ultraviolet detection (HPLC-UV); The expression of proenkephalin(PENK) and prodynorphin(PDYN) mRNA were detected by RT-PCR. The remained tissue of brainswere fixed with 4% paraformaldehyde and the coronally 30um-thick sections from mesencephalon were prepared for immunocvtochemistry(ICC).Tyrosine hydroxylase(TH) and glia fabrillary acidic protein(GFAP) were observed by ICC.The results are as followings:1. SV improved the dyskinesia of PD miceIn the pole test, traction test and the swimming test, the model group(MPTP+NS) mice demonstrated dyskinesia, scores obtained from the threebehavioral tests were decreased significantly compared with control group( NS+NS) ; while the scores in treatment groups ( MPTP+SV) showed a markedincrease to some degree.2. SV protected DAergic neurons in substantia nigra compacta (SNc)The ICC of TH showed that, there were seldom TH positive neurons in SNc (p<0.01) in model group (MPTP+NS) ; while there were much more TH positive neurons presented in the treatment groups ( MPTP+SV20, MPTP+SV200) than that in model group (MPTP+NS) (20mg/kg dose group, p<0.01; 200mg/kg dose group, p<0.01).The contents of DA and HVA were detected by HPLC to be decreased approximately by 70% and the ratio of HVA/DA increased in model group (MPTP+NS ) compared with control group ( NS+NS )(p<0.01); In treatment groups (MPTP+SV), the contents of DA and HVA were recovered significantly and the ratio of HVA/DA decreased. (20mg/kg dose group, p<0.05; 200mg/kg dose group, p<0.01).3. SV prevented the proliferation of astrocyte in SNGFAP positive astrocytes were obviously increased fn SN (p<0.01) by ICC in model group (MPTP+NS) ; Compared with control group (NS+NS) , there was no significantly increase of GFAP positive astrocytes in treatment groups (MPTP+SV) (p<0.01).4. SV increased the expression level of PDYN mRNA in striatumRT-PCR demonstrated that, the level of PDYN mRNA expression in model group (MPTP+NS) was declined markedly (p<0.01). On the contrary, the level of PENK mRNA was increased apparently (p<0.05); in the treatment groups (MPTP+SV) , both PDYN mRNA and PENK mRNA were tended to recover at different degree, especially the PPD mRNA in the treament group with high dos...
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