Therapeutic effect of Melissa officinalis in an amyloid-β rat model of Alzheimer’s disease

Introduction: Medicinal herbs have several components with different pharmacological effects. It has been described that Melissa officinalis is able to improve memory in different models of learning. Nevertheless, its influence has not been studied in animal models of AD. Here, we studied the potential therapeutic effect of M. officinalis in intracerebroventricular (i.c.v) amyloid-β (Aβ) model of Alzheimer’s disease (AD).Methods: Male Wistar rats weighing ۲۶۰-۳۳۰ g received the hydro-alcoholic extract of M. officinalis (۵۰, ۱۰۰, ۲۰۰, ۴۰۰ mg/kg; P.O), chronically for ۳۰ consecutive days. The control group received solvent of the drug. Memory retrieval was assessed, using the passive avoidance task. Three groups of the rats received Aβ (۱-۴۲; ۱۰ μg/rat bilaterally; i.c.v). One group received DMSO ۱% (۲ μL/rat; i.c.v). Twenty days later memory retrieval was assessed. The Aβ-treated rats, received M. officinalis (۵۰, ۱۰۰ mg/kg; P.O) or saline (۱ mL/kg; P.O), chronically for ۳۰ consecutive days. The DMSO ۱%-treated rats received saline (۱ mL/kg; P.O).Results: The hydro-alcoholic extract of M. officinalis (۵۰, ۱۰۰, ۲۰۰, ۴۰۰ mg/kg; P.O) did not have a significant effect on step-through latency (STL). Aβ impaired memory retrieval by decreasing STL and increasing the time spent in the dark compartment (TDC). M. officinalis (۵۰, ۱۰۰ mg/kg; P.O) improved memory retrieval in AD rats by increasing STL and decreasing TDC, significantly.Conclusion: The outcomes of the study show that M. officinalis has a therapeutic effect in the Aβ model of AD. It seems that the extracts of M. officinalis can be suggested as a powerful therapeutic herb for AD patients.