• Modeling Mechanism：

  L-DOPA is a classic drug for treating Parkinson's disease, which is converted into dopamine in the brain to exert its replacement therapy effect. In a hemi-Parkinson's disease (hemi-PD) model constructed by unilateral destruction of striatal dopaminergic neurons with 6-hydroxydopamine (6-OHDA), due to the large number of dopaminergic neurons missing, the dopamine converted from exogenous L-DOPA cannot be reuptaken normally. It is mainly released non-specifically through serotonergic neurons, resulting in an abnormally high concentration of dopamine in the synaptic cleft. Excessive dopamine continuously overactivates downstream signaling of dopamine D1 receptors, leading to abnormal activation of the AKT/mTOR/S6K and CREB/ΔFosB pathways in the striatum (ST), ultimately inducing levodopa-induced dyskinesia (LID), thus simulating the core complication that occurs in clinical Parkinson's disease patients after long-term use of L-DOPA.

• Related Products：

  L-DOPA (T0848)

• Modeling Method：

  Experimental Subject：

  Mice: ICR strain, male, 6 weeks old, body weight 30–34 g

  Dosage and Administration Route：

  ① Core modelling (PD model establishment): 6-OHDA (8 μg/μL) dissolved in physiological saline containing 0.1% ascorbic acid, stereotaxically injected into the right striatum (coordinates: AP 0.5 mm anterior to the anterior fontanelle, ML 2.0 mm lateral, DV -3.0 mm depth), injection rate 0.5 μL/min,total volume 2 μL; sham group (SHAM): physiological saline containing 0.1% ascorbic acid, stereotaxic injection at identical coordinates;
  ② Core modelling (LID model induction): L-DOPA (80 mg/kg)+benzydamine (20 mg/kg) administered orally;
  ③ Group treatment: PD group: 6-OHDA lesionation only, no L-DOPA; LID group: 6-OHDA lesionation+L-DOPA+saline (vehicle control, oral); Positive control group: 6-OHDA lesionation+L-DOPA+amantadine (40 mg/kg, oral).

  Dosing Frequency and Duration Model：

  PD model establishment: Single injection on day 0;
  LID model induction and group treatment: Once daily from day 21 for 28 consecutive days

• Validation：

  1. Behavioral Validation (Core Indicators): - Dyskinesia Score (AIMs Test): The total scores for axial, limb, oral, and motor dyskinesia were significantly higher in the LID group, peaking at 60 minutes, with the total AUC increasing ≥3 times compared to the PD group (p<0.001); - Motor Function Validation (Cylinder Test): The use rate of the contralateral forepaw in the PD group was significantly reduced (≥30% lower than in the SHAM group), recovering after L-DOPA intervention, and the 5-HTP/amantadine group did not affect the motor improvement efficacy of L-DOPA; 2. Molecular Indicators: - Signaling Pathways: The expression of striatal P-AKT (S473), P-mTOR (S2481), P-S6K (T389), P-CREB (S133), and ΔFosB proteins was 2-3 times higher than in the PD group (p<0.01); - Pathway Specificity: Did not affect D1/DARPP32/ERK Signal (distinguishing it from the mechanism of action of amantadine); 3. Histological verification: - Damage rate of striatal dopaminergic neurons ≥70% (verifiable by tyrosine hydroxylase TH immunohistochemistry).

*Precautions： One hour after L-DOPA administration on day 49, the patient was euthanized by cervical dislocation, and the right striatum was rapidly dissected.

*References：Choi Y,et,al. 5-Hydroxytryptophan Reduces Levodopa-Induced Dyskinesia via Regulating AKT/mTOR/S6K and CREB/ΔFosB Signals in a Mouse Model of Parkinson's Disease. Biomol Ther (Seoul). 2023 Jul 1;31(4):402-410.