Effects of Eugenol on Alzheimer's Disease-like Manifestations in Insulin-and Aβ-Induced Rat Models

Eugenol is a phenylpropene having antidepressant properties. We investigated the effect of eugenol on amyloid plaques as a hallmark of Alzheimer’s disease (AD) in two AD rat models. In the latter, betaamyloid (Aβ) and insulin amyloid fibrils were injected into the rat hippocampus. After a one week lapse, the rats were treated with 0.01 and 0.02 mg/kg eugenol for two weeks. Passive avoidance learning and memory performance was assessed by measuring the step-through latency (STL). Amyloid plaques in the hippocampus were quantitatively evaluated and statistically analyzed using image processing software and ANOVA. Aβ amyloid was a more potent inducer of the signs related to Alzheimer’s disease than insulin. Eugenol at a 0.01 mg/kg dose improved memory and reduced the number of amyloid plaques significantly (P < 0.001). Possible mechanisms are proposed for the inhibitory effects of eugenol on hippocampus plaques.