Protective Effects Of Icariin Combined With Total Panax Notoginseng Saponins On Vascular Dementia Rats

The prevalence of dementia grows from 1% in people aged 60 years to about 50% in those aged 95 and older. Vascular dementia (VD) is the second most common form of dementia, ranking after Alzheimer's disease, and is likely to have an increasing impact in an aging population. So far, no effective drugs and therapies have been found to treat the disease. Our previous study showed that icariin combined with panax notoginseng saponins displayed ameliorating effects on Alzheimer's disease model rats induced by β-amyloid peptide 25-35 lateral ventricle injection, so we investigated the neuroprotective effects of this combination on vascular dementia model rats.Based on the pathological mechanisms of vascular dementia (VD) in both Traditional Chinese Medicine and modern medical sciences, as well as the recent studies on the invigorating and nootropic effects of Herba Epimedii (HE) and Radix Notoginseng (RN) or the VD animal models, we adopted the modern isolation methods to study the active components of these two herbs. Icariin (ICA) and panax notoginseng saponins (PNS) were extracted from HE and RN respectively, and by combined administration of two extracts, we further investigated their therapeutic effects on learning and memory capabilities in VD model rats, to provide some experimental evidence for the preventive and therapeutic effects, as well as the relevant mechanisms of the combination in VD treatment.1. Effects of ICA combined with PNS on learning and memory ability of VD rats induced by bilateral common carotid arteries occlusion combined with SNP(i.P.)After trained by eight-arm radial electric maze, rats were operated as above andfollowed by one week of drug treatment. Spatial learning and memory ability were evaluated by eight-arm radial electric maze and step-down passive avoidance taskafter a period of drug therapy. The result showed that the learning and memory abilities of VD rats significantly decreased compared with that in the vehicle-treated group, through eight-arm radial electric maze test (PO.05) and step-down passive avoidance test (PO.05). The combination (ICA+PNS 5+40, 10+80 mg/kg) significantly protected and improved all the evaluated indexes of the model groups after two weeks(PO.05).2. Mechanisms of ICA combined with PNS on spatial learning and memory abilities in VD model rats.2.1 Effects of ICA combined with PNS on whole blood viscosity of VD rats induced by bilateral common carotid arteries occlusion combined with SNP(i-P)After behavioral assay, rats were anesthetized with 10% chloral hydrate (350mg/kg, i.p.) and blood sample was collected from abdominal aorta with syringe. Under shear rate 5s"1 and 30s"1, whole blood viscosity (r^a) of vehicle-treated group increased significantly compared with sham-operated group (P<0.05). Administrations of ICA and PNS combination could significantly lower whole blood viscosity under shear rate 5s"1 and 30s"1 (P<0.05). It suggests that the combination can improve high blood viscosity induced by bilateral common carotid arteries occlusion combined with SNP (i.p.).2.2 Effects of ICA combined with PNS on AchE activity of VD rats induced by bilateral common carotid arteries occlusion combined with SNP (i.p.)Rats were killed by decapitation after blood sample collected. The whole brain was homogenized in 9 vol of ice-cold normal saline. It is shown that treatment with ICA and PNS combination significantly reduced postischemia-enhanced AchE activity as compared to sham-operated group, which suggests that the combination has potential effects on cholinergic protection.2.3 Effects of ICA combined with PNS on ATPase activity of VD rats induced by bilateral common carotid arteries occlusion combined with SNP (i.p.)Rats were killed by decapitation after blood sample collected. The whole brainwas homogenized in 9 vol of ice-cold normal saline. It is shown that ICA+PNS( 10+80 mg/kg) elevated Na+-K+-ATPase activity in the brain(P<0.05), ICA+PNS(5+40 mg/kg) elevated Ca2+-Mg2+-ATPase activity in the brain (PO.05), indicating that the combination has a potential effect on maintaining ion gradients across biological membranes.2.4 Effects of ICA combined with PNS on morphology of hippocampus of VD rats induced by bilateral common carotid arteries occlusion combined with SNP (i.p.)Rats were killed by decapitation 1 week after surgery. In sham-operated animals, CA1 pyramidal neurons were laid in three to four layers and presented round and large nuclei and clear nucleoli. Widespread damage was evident in the repetitive ischemic-reperfusion animals treated with saline. Pyramidal neurons either presented a densely stained shrunken appearance with minimal cytoplasm or had disappeared. In contrast, majority of the CA1 neurons were rescued in rats treated with ICA and PNS combination (5440 mg/kg).2.5 Effects of ICA combined with PNS on plasma ET content of VD rats induced by bilateral common carotid arteries occlusion combined with SNP(i-P)After behavioral assay, rats were anesthetized with 10% chloral hydrate (350mg/kg, i.p.) and blood sample was collected from abdominal aorta with syringe. Plasma ET content was determined by radioimmunometry. It was shown that there was no significant difference between sham-operated and vehicle-treated group, which suggests that the combination took ameliorating effects on VD rats through a ET-independent way.Conclusions1. ICA combined with PNS could significantly improve the spatial learning and memory abilities of VD model rats induced by cerebral repetitive ischemia-reperfusion combined with SNP (i.p.), which suggests that the combination may have preventive and therapeutic effects on VD.2. ICA combined with PNS could significantly improve whole blood viscosity abnormality induced by cerebral repetitive ischemia-reperfusion combined with SNP (i.p.), which suggests that the combination have promoting blood flow effects on VD.3. ICA combined with PNS can inhibit AchE activity of VD rats induced by cerebral repetitive ischemia-reperfusion combined with SNP (i.p.). It suggests that improving cholinergic function may be one of the mechanisms involved in spatial learning and memory abilities improving.4. ICA combined with PNS can elevate ATPase activity of VD rats induced by cerebral repetitive ischemia-reperfusion combined with SNP (i.p.). It suggests that maintaining ion homeostasis may be one of the mechanisms involved in spatial learning and memory abilities improving.5. It was shown that there was no significant difference in plasma ET content after surgery, which suggests that ET wasn't involved in spatial learning and memory abilities improving in this model.