Background: Decreased volume of the hippocampus causes disorders in memory and learning. One of the reasons for the change in the volume of the hippocampus is a change in the number of neurons. Probiotics are living microorganisms whose adequate consumption causes the health effects of the host to appear. Due to the various uses of probiotics and their beneficial effects on the body, they are expected to be able to improve these disorders in cases such as Alzheimer's disease, in which a person's memory and learning are impaired. So, the present study was conducted to investigate the effect of probiotic prophylaxis of Lactobacillus fermentum on neuronal density of hippocampus in CA3, CA2, and CA1 regions in rats with Alzheimer's disease.
Methodology: In the current experimental study, 30 Wistar rats weighing 200-250 g were randomly divided into five groups (control, Alzheimer, 3 treatment groups). In order to induce Streptozotocin Alzheimer, 5 mg/kg doses of stereotaxin (volume of 5 microliters) was injected at each lateral ventricle of the brain. In the treatment groups, Lactobacillus probiotic fermentum was also injected by the dosage of 10^-6, 10^-7, and 10^-8 ML/CFU simultaneous with STZ intraperitoneal injection in 21 days. In the current study, the shuttle box was used to investigate the behavior and to avoid passive learning. One-way analysis of variance (ANOVA) was used to analyze the data resulted from analysis of variance with repetitive measures and to analyze the memory. Data were analyzed using minitab statistical software running Post hoc and ANOVA at a significance level of P<0.05. The curves were drawn using Excel software.
Findings:  A significant decrease was found in the neuronal density of the control group against Alzheimer's group (STZ) (P <0.001), and the comparison between treatment groups (10^-6, 10^-7, 8^-8) and Alzheimer's group (STZ) showed a significant increase (P <0.001).
Conclusion:  It seems that probiotics, with their antioxidant and anti-inflammatory effects, have prevented the development of neuronal lesions and implemented improvement mechanisms. Our study shows that probiotic Lactobacillus fermentum at dilution of 10^-6 has a neurogenic effect and may be used to improve memory and learning.