1 Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China 
2 Department of Anatomy, Chongqing Medical University, Chongqing 400016, China 
3 Department of Neurology, the Affiliated Hospital of Zunyi Medical College, Zunyi 563003, China

Abstract 

Objective 
Nitric oxide (NO) was speculated to play an important role in the pathophysiology of cerebral ischemia. Minocycline, a tetracycline derivative, reduced inflammation and protected against cerebral ischemia. To study the neuroprotection mechanism of minocycline for vascular dementia, the influences of minocycline on expressions of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) were observed in the brains of Wistar rats. 
Methods 
The vascular dementia rat model was established by permanent bilateral common carotid arteries occlusion (BCCAO). Wistar rats were divideded into 3 groups randomly: sham-operation group (S group), vascular dementia model group (M group), and minocycline treatment group (MT group). The behaviour was tested with Morris water maze and open-field task. Expressions of iNOS and eNOS were measured by immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). The optical density value was measured by imaging analysis. Percentage of positive cells with iNOS and eNOS expression was analyzed with optical microscope. 
Results 
Minocycline attenuated cognitive impairment. Inducible NOS was significantly down-regulated in MT group, compared with that in M group (P < 0.01), while eNOS was significantly up-regulated, compared with that in M group (P < 0.01). The expressions of iNOS and eNOS in M and MT groups were higher than those in S group (P < 0.01). 
Conclusion 
Minocycline can down-regulate the expression of iNOS and up-regulate the expression of eNOS in vascular dementia, which restrains apoptosis and oxidative stress to protect neural function.

Keywords

vascular dementia; minocycline; nitric oxide synthase

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