Objective

2

To observe the effects of "olfactory three needles" on cognition

learning and memory abilities

as well as hippocampal microglia (MG) phagocytic activity in vascular dementia (VD) rats

and explore the mechanisms of acupuncture in regulating MG activation and improving remyelination

so as to ameliorate VD.

Methods

2

Among 38 SD rats meeting experimental requirements

9 rats were randomly assigned to a sham-operation group

and the remaining rats underwent permanent bilateral common carotid artery ligation to establish VD model. Eighteen successfully modeled rats were randomly divided into a model group and an electroacupuncture (EA) group

with 9 rats in each one. In the EA group

EA was performed at "olfactory three needles" ("Yintang" [GV24

+

]

and bilateral "Yingxiang" [LI20

]

)

at disperse-dense wave

the frequency of 2 Hz/15 Hz and the current intensity of 1 mA

for 15 min per intervention

once daily. One course was composed of 7 days

and 2 courses were required

with the interval of 2 days. The novel object recognition test was employed to assess the cognition of rats

and the Morris water maze was adopted to observe learning and memory abilities. Luxol fast blue (LFB) staining was performed to evaluate myelin sheath loss in the hippocampus

the Western blot was used to detect the protein expression of triggering receptor expressed on myeloid cells-2 (TREM2) and proteolipid protein (PLP) in the hippocampus; and the immunofluorescence staining was used to detect the positive expression of PLP

sex determining region Y-box 10 (SOX10)

ionized calcium binding adaptor molecule 1 (Iba1)

+

TREM2

+

and Iba1

+

lysosome-associated membrane protein 1 (LAMP1)

+

in the hippocampus.

Results

2

Compared with the sham-operation group

the rats in the model group exhibited the prolonged escape latency on day 3 and 4 (

P

<

0.05

P

<

0.01)

the increase of the total distance traveling (

P

<

0.01) and the decrease of the recognition index (RI) and platform crossing frequency (

P

<

0.01). Compared with the model group

the rats in the EA group showed the shortened escape latency on day 3 and 4 (

P

<

0.05)

the decrease of total distance traveling (

P

<

0.01) and the increase of RI and platform crossing frequency (

P

<

0.05

P

<

0.01). When compared with the sham-operation group

the rats of the model group presented uneven staining

sparse arrangement of myelin sheath fibers

unclear contours

and prominent vacuole-like changes in the hippocampal CA1 region. When compared with the model group

the EA group showed more dense staining

the increase of myelin sheath fibers with more orderly alignment

and fewer vacuolar changes in the hippocampal CA1 region. Compared with the sham-operation group

the model group exhibited the increase of TREM2 protein expression and the decrease of PLP protein expression in the hippocampus (

P

<

0.01)

whereas the EA group showed the up-regulation of TREM2 and PLP protein expression when compared with the model group (

P

<

0.01

P

<

0.05). The positive expression of the hippocampal PLP

SOX10

and Iba1

+

LAMP1

+

in the model group was reduced in comparison with the sham-operation group (

P

<

0.05

P

<

0.01)

and the positive expression of Iba1

+

TREM2

+

was elevated (

P

<

0.05). In the EA group

the positive expression of PLP

SOX10

Iba1

+

TREM2

+

and Iba1

+

LAMP1

+

was higher compared with that in the model group (

P

<

0.05

P

<

0.01).

Conclusion

2

"Olfactory three needles" can improve the learning and memory

and cognitive functions of VD rats

and its mechanism may be associated with the up-regulation of TREM2 and LAMP1 to adjust MG phagocytic activity and intracellular degradation

and promote remyelination.