Effects of xiusanzhen acupuncture on hippocampal CA1 region damage and microglia activation in rats with vascular dementia: A trigeminal nerve perspective

This study aimed to observe the effects of xiusanzhen acupuncture (olfactory three-needling therapy) on the behavior, hippocampal histopathology and microglial (MG) activation of rats with vascular dementia (VD), and to assess the role of the trigeminal nerve. Sprague-Dawley (SD) rats were randomly assigned to the sham-operation, model, xiusanzhen , and trigeminal neurotomy groups ( n = 15 per group). Bilateral common carotid artery ligation was performed to prepare the VD models. Models of trigeminal neurotomy were prepared through the excision of the frontal nerve and infraorbital nerve. Xiusanzhen acupuncture was delivered via electric stimulation. The acupoints selected were bilateral “Yingxiang (LI20)” and “Yintang (EX-HN3)”, and the stimulation parameters were as follows: disperse-dense wave, at a frequency of 2/15HZ and intensity of 1 mA. The course of treatment was once daily, with one course lasting five days, followed by an interval of two days, yielding a total of four courses. Behavioral changes were detected using the Morris water maze, changes in histomorphology in the hippocampal CA1 region were determined with hematoxylin and eosin (HE) staining, and MG activation in the hippocampal CA1 region was detected using immunofluorescence. The escape latency: From days 3 to 5, the escape latency was higher in the model group compared to the sham-operation group ( P < 0.05), but was lower in the xiusanzhen group compared to the model and trigeminal neurotomy groups ( P < 0.05). The frequency for platform crossing and swimming distance: both were reduced in the model group compared to the sham-operation group ( P < 0.01); and were elevated in the xiusanzhen group compared to the model group and trigeminal neurotomy group ( P < 0.01). Hippocampal pathomorphological changes: In the sham-operation group, the morphological structure and nucleoli were well-defined; in the model group and the trigeminal neurotomy group, cell numbers were reduced and karyopyknosis increased; while in the xiusanzhen group, the cell numbers were elevated and karyopyknosis was reduced compared with the model group. MG: the positive rate was higher in the model group compared to the sham-operation group ( P < 0.05); lower in the xiusanzhen group compared to the model group ( P < 0.05); and higher in the trigeminal neurotomy group compared to the xiusanzhen group ( P < 0.05). Xiusanzhen acupuncture attenuates cognitive impairment in VD rats, inhibits MG activation, and reduces hippocampal tissue damage. Its effects depend on the structural integrity of the trigeminal nerve.