Protective Effects of Oral Vitamin C on Memory and Learning Impairment and Attenuation of Synaptic Plasticity induced by Intracerebroventricular Injection of Beta-amyloid Peptide in Male Rats

Abstract

Background: In neurodegenerative diseases, like Alzheimer’s disease (AD), learning and memory, and neural plasticity are impaired. Vitamin C (Vit C), as an antioxidant, protects tissues against oxidative stress. In this study, the neuroprotection and the effectiveness of Vit C in the prevention and treatment of AD in a rat model of AD induced by intracerebroventricular (ICV) injection of amyloid-beta (Aβ) were studied using behavioral tests and electrophysiological methods. Methods: 50 male Wistar rats were randomly assigned to five groups (n=10 rats /group): Control, Sham, AD, Vit C, and AD+Vit C. After treatment (2 months), animals were assessed by learning and memory tests, including the new object recognition (NOR), passive avoidance learning (PAL), and Morris water maze (MWM) tests. Then, using the electrophysiological method, synaptic plasticity in the hippocampus was assessed and Vit C effects on long-term potentiation (LTP) were examined.Results: ICV injection of Aβ to the AD group reduced memory in the NOR, PAL, and MWM behavioral tests. Also, Vit C reduced learning and memory impairment due to Aβ injection in rats. Aβ caused the inhibition of LTP in dentate gyrus (DG) granule cells by reducing the slope of the excitatory postsynaptic potential (EPSP) and the amplitude of the population spike (PS) in the AD group. Conclusions: These results showed that Vit C reduced the impairment in synaptic plasticity induced by Aβ in DG of the hippocampus. Vit C supplementation through its antioxidant properties can improve the impaired synaptic plasticity and memory induced by Aβ and can be applied as a neuroprotective agent.