Research reportHigh frequency electro-acupuncture enhances striatum DAT and D1 receptor expression, but decreases D2 receptor level in 6-OHDA lesioned rats

The direct effects of electro-acupuncture (EA) on the dopaminergic neurotransmitter system in Parkinson's disease (PD) patients remain elusive. In the present study, 0, 2 or 100 Hz EA was applied to acupoints Sanyinjiao (SP6), Yanglingquan (GB34) and Zusanli (ST36) in a rat model unilaterally lesioned by 6-hydroxydopamine. Rotational behavior tests were performed and the animals were then decapitated. Levels of striatal dopamine (DA), dopamine transporter, and D1- and D2-like DA receptors were subsequently evaluated. EA at 100 Hz was shown to significantly enhance survival of dopaminergic neurons in the substantia nigra (52.10 ± 11.41% of the level on the non-lesioned rats vs. 21.22 ± 5.52% in the non-EA group, P < 0.05) and reduce motor deficits (207.80 ± 31.14 vs. 476.11 ± 68.80 turns/30 min, P < 0.05), whereas it only slightly restored the 6-hydroxydopamine-induced loss of striatal DA (P > 0.05 vs. the non-EA group). There was a 253.78% increase in dopamine transporter protein expression in the striatum in the 100 Hz EA group (P < 0.05 vs. the non-EA group). Moreover, high frequency EA induced increases in striatal D1-like receptor mRNA and protein levels of 81.88% and 62.62%, respectively (P < 0.001 and P < 0.05 vs. the non-EA group). However, the D2-like DA receptor up-regulation observed in the non-EA group was suppressed in high frequency group (P > 0.05 vs. the sham operation group). These findings suggest that high-frequency EA might work by acting on presynaptic dopamine transporter and postsynaptic dopamine receptors simultaneously to achieve a therapeutic effect in PD patients and models. This might shed some light on the mechanism by which EA affects the DA neurotransmitter system.

► 100 Hz EA halted DA neuron degeneration, improved behavior in 6-OHDA lesioned rats. ► 100 Hz EA raised the DA level in the ST although the difference was not significant. ► High frequency EA increases the DAT level in the ST and SN simultaneously. ► 100 Hz EA suppressed D2R up-regulation secondary to 6-OHDA lesioning. ► The D1R expression level was obviously elevated after high-frequency EA.