Antiamnesic and Neuroprotective Effects of an Aqueous Extract of Ziziphus jujuba Mill. (Rhamnaceae) on Scopolamine-Induced Cognitive Impairments in Rats.

Etienne Djeuzong,Théophile Dimo,Lewale Stéphanie,Jean P Djientcheu,Danide Nguedia,Antoine K Kandeda,Jonas Kouamouo,Séfirin Djiogue,Florence Ngueguim,Alin Ciobica

doi:10.1155/2021/5577163

Abstract

Background Alzheimer's disease is a neurological condition that affects about 44 million people worldwide. The available treatments target symptoms rather than the underlying causes. Ziziphus jujuba (Rhamnaceae) is widely used in traditional Cameroonian medicine to treat diabetes, pain, infections, and dementia. Previous studies reported that Z. jujuba aqueous macerate improves working memory impairment, but no study on the antiamnesic effect of a concoction of Z. jujuba in rats has been performed. Therefore, this study aimed to assess the antiamnesic and neuroprotective effects of an aqueous extract of Z. jujuba on scopolamine-induced cognitive impairments in rats. Methods Learning and memory impairments were induced in rats by administering scopolamine (1 mg/kg, i.p.) to 58 rats for 15 days. Rats that developed learning and memory impairments in Morris water maze and Y-maze paradigms were divided into 7 groups (8 rats each) and treated daily for 15 days as follows: the normal control group received distilled water (10 ml/kg, p.o.), the negative control group received distilled water (10 ml/kg, p.o.), positive control groups either received donepezil (1.2 mg/kg, p.o.) or tacrine (10 mg/kg, p.o.), and the three test groups were given the extract (29, 57, and 114 mg/kg, p.o.). At the end of treatments, learning and memory impairments were determined using the same paradigms. Animals were then euthanized, and biochemical parameters of oxidative stress, inflammation, and apoptosis were analyzed in the hippocampus and prefrontal cortex. Results On the 4th day of the acquisition phase in the Morris water maze, Z. jujuba (29 and 114 mg/kg) reduced (p < 0.001) the latency to reach the platform, while in the retention phase, Z. jujuba (57 and 114 mg/kg) decreased (p < 0.001) the time to reach the platform and increased the time in the target quadrant (p < 0.05) compared to control. Surprisingly, the extract failed to affect spontaneous alternations in the Y-maze. Furthermore, the extract (29, 57, and 114 mg/kg) reversed (p < 0.001) scopolamine-induced oxidative stress, inflammation, and apoptosis. This was supported by the reduction of neuronal alterations in the hippocampus and prefrontal cortex. Conclusions Compared to donepezil, a standard drug against Alzheimer's disease, these findings suggest that Z. jujuba extract possesses antiamnesic and neuroprotective effects, and these effects are mediated in part through antioxidant, anti-inflammatory, and antiapoptotic activities. These findings help to explain its use in treating psychiatric disorders in Cameroon's folk medicine.

Highlights

Alzheimer’s disease (AD) is the most common form of dementia (60–70% of cases) [1]
Administration of scopolamine in the negative control group significantly (p < 0.001) increased the latency to reach the platform when compared to the normal control group (Figure 2(a))
Previous studies demonstrated that an aqueous macerate of Z. jujuba alleviates working memory impairment and restores neurochemical changes in the prefrontal cortex of D-galactosetreated rats [22]

Summary

Introduction

Alzheimer’s disease (AD) is the most common form of dementia (60–70% of cases) [1]. It is an irreversible and progressive neurodegenerative disorder of the central nervous system that occurs gradually and leads to memory loss, unusual behavior, and personality changes [1, 2]. Scopolamine, a muscarinic cholinergic receptor antagonist, is used as a pharmacological experimental model for inducing cognitive impairments and memory disorders in animals. Cognitive behaviors, such as ataxia, anxiety, depression, short-term memory, reference memory, and attention are affected by injections of scopolamine in rodents [1]. Both the hippocampus and prefrontal cortex are susceptible to oxidative stress, and excessive oxidative stress induces memory deficiency by damaging synaptic plasticity and causing inflammation and neuronal cell death [2]. A standard drug against Alzheimer’s disease, these findings suggest that Z. jujuba extract possesses antiamnesic and neuroprotective effects, and these effects are mediated in part through antioxidant, anti-inflammatory, and antiapoptotic activities. ese findings help to explain its use in treating psychiatric disorders in Cameroon’s folk medicine

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