Policosanol protects against Alzheimer's disease-associated spatial cognitive decline in male rats: possible involved mechanisms.

RATIONALE: Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by cognitive decline and synaptic failure. OBJECTIVE: The present study was designed to explore the possible protective effects of policosanol (PCO) on spatial cognitive capacity, long-term potentiation (LTP) induction, oxidant/antioxidant status, and Aß plaques formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aß1-40. METHODS: Healthy adult male Wistar rats were randomly divided into control, sham (ICV injection of 5 µl phosphate-buffered saline), AG (50 mg/kg; P.O., as PCO vehicle), PCO (50 mg/kg; P.O.), AD model (ICV injection of 5 µl Aß), AD + AG (50 mg/kg; P.O.), and AD + PCO (50 mg/kg; P.O.). Treatments were performed for eight consecutive weeks. At the end of the treatment course, spatial learning and memory functions, hippocampal long-term potentiation (LTP) induction, malondialdehyde (MDA), and total thiol group (TTG) levels, as well as the formation of Aß plaques, were examined. RESULTS: The results showed that injection of Aß reduced spatial learning and memory abilities in the Barnes maze test, which was accompanied by decreases in field excitatory postsynaptic potential (fEPSP) slope, population spike (PS) amplitude, and TTG level and increases in Aß plaque accumulation and MDA content. In contrast, PCO treatment improved all the above-mentioned changes in the Aß-infused rats. CONCLUSIONS: The results suggest that amelioration of hippocampal synaptic plasticity impairment, modulation of oxidant/antioxidant status, and inhibition of Aß plaque formation by PCO may be the mechanisms behind its protective effect against AD-associated spatial cognitive decline.

The Protective Effects of Policosanol on Learning and Memory Impairments in a Male Rat Model of Alzheimer's Disease.

Alzheimer's disease (AD), the most common form of dementia, is characterized by a progressive decline in cognitive performance and memory formation. The present study was designed to investigate the effect of policosanol (PCO) on cognitive function, oxidative-antioxidative status, and amyloid-beta (Aß) plaque formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aß1-40. Healthy adult male Wistar rats were randomly divided into seven groups: control, sham (5 µL, ICV injection of phosphate-buffered saline), AD model (5 µL, ICV injection of Aß), acacia gum (50 mg/kg, 8 weeks, gavage), PCO (50 mg/kg, 8 weeks, gavage), AD + acacia gum (50 mg/kg, 8 weeks, gavage), and AD + PCO (50 mg/kg, 8 weeks, gavage). During the ninth and tenth weeks of the study, the cognitive function of the rats was assessed by commonly used behavioral paradigms. Subsequently, oxidative-antioxidative status was examined in the serum. Moreover, compact Aß plaques were detected by Congo red staining. The results showed that injection of Aß impaired recognition memory in the novel object recognition test, reduced the spatial cognitive ability in the Morris water maze, and alleviated retention and recall capability in the passive avoidance task. Additionally, injection of Aß resulted in increased total oxidant status, decreased total antioxidant capacity, and enhanced Aß plaque formation in the rats. Intriguingly, PCO treatment improved all the above-mentioned neuropathological changes in the Aß-induced AD rats. The results suggest that PCO improves Aß-induced cognitive decline, possibly through modulation of oxidative-antioxidative status and inhibition of Aß plaque formation.

Sex differences in spatial learning and memory and hippocampal long-term potentiation at perforant pathway-dentate gyrus (PP-DG) synapses in Wistar rats.

BACKGROUND: Recent studies show that gender may have a significant impact on brain functions. However, the reports of sex effects on spatial ability and synaptic plasticity in rodents are divergent and controversial. Here spatial learning and memory was measured in male and female rats by using Morris water maze (MWM) task. Moreover, to assess sex difference in hippocampal synaptic plasticity we examined hippocampal long-term potentiation (LTP) at perforant pathway-dentate gyrus (PP-DG) synapses. RESULTS: In MWM task, male rats outperformed female rats, as they had significantly shorter swim distance and escape latency to find the hidden platform during training days. During spatial reference memory test, female rats spent less time and traveled less distance in the target zone. Male rats also had larger LTP at PP-DG synapses, which was evident in the high magnitude of population spike (PS) potentiation and the field excitatory post synaptic potentials (fEPSP) slope. CONCLUSIONS: Taken together, our results suggest that sex differences in the LTP at PP-DG synapses, possibly contribute to the observed sex difference in spatial learning and memory.

Effects of vanillic acid on Aß1-40-induced oxidative stress and learning and memory deficit in male rats.

Alzheimer's disease (AD) is a neurodegenerative disease, in which the accumulation of ß-amyloid (Aß) peptide in the extracellular space causes a progressive reduction in cognitive performance. Aß stimulates active oxygen species generation leading to oxidative stress and neural cell death. Vanillic Acid (VA) is the oxidant form of vanillin widely found in vanilla beans. VA has many properties, such as suppressing apoptosis and eliminating the harmful effects of oxidative stress in animal models. The VA effects on impaired learning and memory in Aß rats were assessed. Forty adults male Wistar rats were assigned to the following five groups in random: the control, sham (received saline (vehicle) via intracerebroventricular (ICV) injection), Aß (received Aß1-40 via ICV injection), VA (50 mg/kg by oral gavage once a day through four weeks), and Aß + VA (50 mg/kg) groups. Open field test, novel object recognition (NOR) test, Morris water maze (MWM) test, and passive avoidance learning (PAL) task were performed, and finally, we determined the malondialdehyde (MDA), total antioxidant capacity (TAC) and total oxidant status (TOS) levels. Aß decreased the cognitive memory in NOR, spatial memory in MWM, and passive avoidance memory in PAL tests. In contrast, VA improved learning and memory in the treated group. Aß significantly increased MDA and TOS and decreased TAC levels, whereas VA treatment significantly reversed TAC, TOS and MDA levels. In conclusion, VA decreased the Aß effects on learning and memory by suppressing oxidative stress and can be regarded as a neuroprotective substance in AD.

Vanillic acid attenuates amyloid ß1-40-induced long-term potentiation deficit in male rats: an in vivo investigation.

Objectives: Alzheimer disease (AD) is a neurodegenerative disorderliness that involves deductible progressive cognition function caused by amyloid-beta (Aß) peptide accumulation in the interstitial space. The increase of Aß stimulates all kinds of active oxygen and causes oxidative stress and apoptosis. In this investigation, we researched the neuroprotective impacts of vanillic acid (VA) on the Aß-induced (Aß1-40) long-term potentiation (LTP) of the hippocampus - a commonly probed synaptic plasticity model that happens at the same time as memory and learning - in the AD rats.Methods: Forty-five male Wistar rats were categorized into five groups (n = 8 rats/group, 200-220 g), and studied as control (standard diet), sham (vehicle), VA (50 mg/kg), Aß and Aß + VA (50 mg/kg) groups. In vivo electrophysiological recordings were implemented after the stereotaxic surgery to gauge the excitatory postsynaptic potential (EPSP) slope and population spike (PS) amplitude in the dentate gyrus of the hippocampus. By the stimulation at high-frequency of the perforate pathway, long-term potentiation (LTP) was induced. To assess the plasma levels of malondialdehyde (MDA) and total thiol group (TTG), blood samples were garnered.Results: In the Aß-injected rats, EPSP slope, and PS amplitude were significantly reduced after the induction of LTP. Thus, the findings demonstrate that VA decreases the impacts of Aß on LTP; also, the treatments through VA neuroprotective against the negative effects of Aß on the synaptic plasticity of the hippocampus can decrease the MDA levels and also increase the TTG levels significantly.Discussion: Therefore, based on this experiment on male rats, VA has neuroprotective effects and antioxidants benefits against the Aß-mediated inhibition of long-term potentiation.