Effects of electroacupuncture on synaptic plasticity of hippocampal neurons in model rats with Alzheimer disease

Song LUO; Shuguang YU; Ting HAN

ABSTRACT

BACKGROUND:

Electroacupuncture has a good clinical effect on Alzheimer disease, but its mechanism remains unclear.

OBJECTIVE:

To observe the effect of electroacupuncture on number of synaptic numeric density (Nv), surface density (Sv) and average size of synaptic conjunction and ultrastructure in hippocampal CA3 area of neurons of model rats with Alzheimer disease (AD).

DESIGN:

Completely randomized grouping and controlled study.

SETTING:

Department of Traditional Chinese Medicine of Sichuan Provincial People's Hospital; College of Acupuncture & Moxibustion and Massage of Chengdu University of Traditional Chinese Medicine.MATERIALS A total of 50 male SD rats of 24-month old weighing (480±20) g and 6 male rats of 3-month old weighing (250±15) g were selected in this study. Passage water maze (2.1×1.7×0.6) m3 was made of black glasses with 40 cm deep water and 4 caecums. WQ1002F Hans electrically heated distilling apparatus was used.

METHODS:

The experiment was carried out at the Grade Ⅲ Animal Experimental Center of Chengdu University of Traditional Chinese Medicine between, September 2002 and June 2003. ① Old SD rats were grouped on the basis of water-maze test results. Firstly, 6 young rats were submitted to water-maze test at 8 days before modeling for 4 continuous days to obtain average escaping latency. Secondly, 50 old rats were accepted in the water-maze test at 4 continuous days before modeling to obtain average escaping latency. A total of 36 rats whose latencies were less than average values plus one standard deviation of young rats were regarded as normal old rats. Among them, 12 rats were randomly divided into control group and sham operation group with 6 in each. Another 24 rats were transected at fornix-fimbria AD modeling. Thirdly, 24 modeling rats were all adopted in the water-maze test at 2 days after modeling. Rats whose latencies were more than average value plus two standard deviation of young rats were chosen as AD model. Twelve AD models were randomly divided into model group and electroacupuncture group with 6 in each.② On the 6th day after modeling, rats in electroacupuncture group were acupunctured at Baihui (Du20) of 0.5 inch in slope, Yongquan (K1),Taixi (K3) and Xuehai(Sp10) of 0.3 inch in depth with No. 30 milli-needle (3.33 cm); Then, electrically heated distilling apparatus was used with successive waves, 20 Hz in frequency and 2-4 V in voltage. Tolerant stress of rats at quiet state was regarded as the standard value (2 mA),the needle was maintained for 30 minutes, and the acupuncture was done once a day for totally 20 successive days. Rats in control group sham operation group (cerebral cortex was exposured at the same site as model rats, and fornix-fimbria was not cut off) and model group were only fixed but treated with nothing. ③ After treatment, ultrastructure in hippocampal CA3 area of rats was observed with transmission electron microscope;synapse numbers and cross-point numbers between synaptic conjunction and test line were counted with stereological technique; stereological parameters, such as numeric density (Nv), area surface (Sv) and average size of synaptic conjunction, which could reflect plastic changes of synaptic form, were calculated at the same time. ④ Differences between every two groups were compared with t test at regular variance and t'test at irregular variance.MAIN OUTCOME

MEASURES:

Comparisons of numeric density (Nv),surface density (Sv) and average size of synaptic conjunction.

RESULTS:

A total of 24 old rats were involved in the final analysis with 6 in each group. ① Ultrastructure Synaptic density of control and sham operation group was higher than that of model group, and average area of synapse was smaller;, synaptic density of electroacupuncture group increased compared with that of model group, and average area of synapse was smaller. ② Numeric density and surface density in hippocampal CA3 area in model and electroacupuncture group were lower than those of control group and sham operation group (P ＜ 0.05). There was no significant difference between sham operation group and control group (P ＞ 0.05), and those of electroacupuncture group were higher than those of model group (P ＜ 0.01). ③ Average size of synaptic conjunction in hippocampal CA3 of model and electroacupuncture group was higher than that of control and sham operation group (P ＜ 0.05). There was no significant difference between sham operation group and control group (P ＞ 0.05), and the value of electroacupuncture group was lower than that of model group (P ＜ 0.01).

CONCLUSION:

Electrotherapy can repair synaptic form and inhibit synaptic degeneration of hippocampal neurons in AD rats.