Evaluation Of Motor Coordination And Gastrointestinal Function In Parkinson’s Disease Transgenic Mice Carrying Human Mutant Alpha-synuclein(A53T)

Parkinson’s disease(PD) is one of the most common neurodegenerative diseases, with a prevalence rate around 2% among people aged over 60, and even more higher in elderly people. PD is characterized pathologically by the selective loss of dopaminergic neurons in the substantia nigra(SN) and the depletion of striatal dopamine content. Alpha-synuclein is persistently found to be the major component of the hallmark neuronal inclusions named Lewy bodies.It is widely accepted that Braak proposed a staging procedure for the inclusion body pathology associated with PD. The Lewy body pathology appears in the SN and other nuclein of the basal mid- and forebrain when the disease progresses to the SN in stage 3 to 4, which is related to the motor symptoms PD patients diagnosed clinically. In sporadic PD patients, before the movement symptoms, 98.6% of the patients can suffer from several non-motor symptoms, including dysosmia, constipation, sleep disorders, cardiovascular dysfunction and so on. The non-motor symptoms are attracting more attention. The gastrointestinal dysfunction is most popular among the non-motor symptoms with more than 80% incidence, especially delayed gastric emptying, which is found in 70%-100% PD patients.In the present study, we investigated whether and when movement behavior and gastrointestinal dysfunction occurred in the PD transgenic mice carrying human mutant alpha-synuclein(A53T). We also aimed to unveil the central mechanism of gastrointestinal dysfunction in PD. To explore this issue, we evaluated the changes of motor coordination by rotarod test and observed the number of dopaminergic neurons in the SN by immunofluorescent methods. Using gastric emptying and small intestinal propulsion method, we detected the gastrointestinal function. The results were as follows:1. Identification of A53 T PD transgenic mice by polymerase chain reaction. The samplefrom transgenic mice showed a bright band in 248 bp, which coincided with the expected position of mutant alpha-synuclein c DNA fragments. These results confirmed that mutant alpha-synuclein gene has been integrated into the mice genome, and can be stable in batches.2. The residence time of female A53 T PD transgenic mice of 23-24 months on rotating treadmills was decreased by 75% compared with that of the age- and sex- matched WT mice(P<0.05). There was no difference observed in 16-17 months and 19-20 months female A53 T PD transgenic mice when compared with WT mice.3. The residence time of 19-20 months male A53 T PD transgenic mice on rotating treadmills was decreased by 55% compared with that of the age- and sex- matched WT mice(P<0.05). There was no difference observed in 12-13 months and 16-17 months male A53 T PD transgenic mice when compared the WT mice.4. The number of dopaminergic neurons in the SN was observed decreased by 15.4% and 20.1% in 17 months and 19 months female PD transgenic mice, respectively, compared with the age- and sex- matched WT mice(P<0.05). However, no difference was observed in 12 months and 15 months groups.5. The number of dopaminergic neurons in the SN was decreased by 18.90%, 22.30% and 38.0% in 15 months, 17 months and 19 months male PD transgenic mice, respectively, compared with that of the age- and sex- matched WT mice(P<0.05). No difference was observed in 12 months group.6. Gastric emptying rate in 17 months female PD transgenic mice was increased by 50% compared with WT mice(P<0.05). No difference was observed in 15 months and 19 months group. Small intestinal motility in 15 months female A53 T PD transgenic mice was decreased by 24.8% compared with WT mice(P<0.05). No difference of small intestinal motility was observed in 17 months and 19 months groups.7. Gastric emptying rate in 15 months male A53 T PD transgenic mice was observed increased by 45% compared with the corresponding WT mice(P<0.05). However, gastric emptying rate in 17 months male A53 T PD transgenic mice was decreased by 30%, compared with WT mice(P<0.05). No significant difference of small intestinal motility was observed in 15 months and 17 months groups.These results suggest that both movement coordination and gastrointestinal function impairment occurred earlier in male A53 T PD transgenic mice when compared to female transgenic mice. Movement coordination disorders were accompanied by the decreased number of dopaminergic neurons, which proceeded gastrointestinal dysfunction. The results show that gastrointestinal dysfunction in early stages of PD might be the target of PD early diagnosis and intervention. The mechanisms underlying gastrointestinal dysfunction remains to be further investigated in the early stages of PD.