High 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. (C) 2012 Elsevier B.V. All rights reserved.