Electroacupuncture Alleviates Motor Symptoms and Up-Regulates Vesicular Glutamatergic Transporter 1 Expression in the Subthalamic Nucleus in a Unilateral 6-Hydroxydopamine-Lesioned Hemi-Parkinsonian Rat Model

Abstract

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.

Keywords: Electroacupuncture; Motor behavior; Parkinson’s disease; Vesicular glutamate transporter 1.

Fig. 1

EA at 100 Hz significantly reversed the motor deficits in hemi-parkinsonian rats. A 100 Hz but not 0 Hz EA significantly reversed APO-induced rotational behavior in hemi-parkinsonian rats. B 100 Hz but not 0 Hz EA significantly reversed the latency to falling in the Rotarod test of hemi-parkinsonian rats. Data represent mean ± SEM (n = 10–12 per group; *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001 versus sham rats; ^#P < 0.05 and ^##P < 0.01 versus 100 Hz EA-treated rats).

Fig. 2

EA at 100 Hz had no significant effect on TH expression levels in the SNc and striatum of hemi-parkinsonian rats. A, C Neither 100 Hz nor 0 Hz EA stimulation had significant effects on TH-positive profiles in the lesioned (right) striatum of hemi-parkinsonian rats as shown by immunohistochemical staining. B, D Neither 100 Hz nor 0 Hz EA stimulation had significant effects on TH-positive neurons in the lesioned SNc of hemi-parkinsonian rats as shown by immunohistochemical staining. Scale bars, 1 mm in A and 500 μm in B. Data represent mean ± SEM (n = 4/group; ****P < 0.0001 versus sham rats).

Fig. 3

EA at 100 Hz had no significant effect on the trans-synaptic infection of HSV-GFP neurons in the lesioned STN of hemi-parkinsonian rats. A Neither 100 Hz nor 0 Hz EA had significant effects on the trans-synaptic infection of HSV-GFP neurons in the lesioned STN of hemi-parkinsonian rats as shown by HSV-GFP tracing. B Neither 100 Hz nor 0 Hz EA stimulation had significant effects on the number of trans-synaptically infected HSV-GFP neurons in the lesioned STN of hemi-parkinsonian rats. C Neither 100 Hz nor 0 Hz EA stimulation had significant effects on the normalized number of trans-synaptically infected HSV-GFP neurons in the lesioned STN (the number of HSV-GFP neurons in the STN per 10,000 starter cells in the M1) of hemi-parkinsonian rats. Scale bars, 200 μm. Data represent mean ± SEM (n = 4/group; ****P < 0.0001 versus sham rats on the same ipsilateral (right) side).

Fig. 4

EA at 100 Hz up-regulated VGluT1 expression levels in the lesioned STN of hemi-parkinsonian rats. A, B 100 Hz but not 0 Hz EA up-regulated the expression of VGluT1 protein in the lesioned STN of hemi-parkinsonian rats as shown by Western blotting. C, D 100 Hz but not 0 Hz EA up-regulated the expression of VGluT1 protein in the lesioned STN of hemi-parkinsonian rats as shown by immunohistochemical staining. Data represent mean ± SEM (n = 4/group; *P < 0.05, **P < 0.01 versus sham rats; ^#P < 0.05, ^##P < 0.01 versus 100 Hz EA-treated rats).