Cognitive enhancing, anti-acetylcholinesterase, and antioxidant properties of Tagetes patula on scopolamine-induced amnesia in mice

Abstract

Background: Alzheimer’s disease is a progressive neurodegenerative disorder characterized by a gradual decline in memory associated with shrinkage of brain tissue and loss of neurons with a diminished level of the central cholinergic neurotransmitter acetylcholine. Objective: The present study was performed to examine the effect of ethanolic extract of Tagetes patula (EETP) on cognitive impairment induced by scopolamine, a muscarinic antagonist, in mice. Materials and Methods: Rats were treated with EETP and donepezil for 15 successive days followed by treatment with scopolamine (1 mg/kg) for 3 days. The changes in behavioral, biochemical, and neurotransmitters were assessed in rats. Cognitive functions were assessed using step‐through latency on a passive avoidance apparatus and Morris water maze test. Antioxidants parametes such as superoxide dismutase (SOD), glutathione reductase (GR), lipid peroxidation (LPO), and nitrates were assessed. Neurotransmitters including acetylcholinesterase (AChE), dopamine (DA), and serotonin were also assessed, and neuronal damage was also analyzed. Results: Scopolamine‐treated rats showed impaired learning and memory, increased activity of AChE, LPO and decreased levels of SOD, reduced glutathione, nitrates, serotonin, and DA. The EETP significantly reversed the scopolamine‐induced cognitive impairment in mice was measured by the passive avoidance test. In addition, EETP decreased escape latency in the Morris water maze. In probe trail session, EETP increased the latency time in the target quadrant. Ex vivo EETP inhibited AChE activity in the mice brain. EETP treated mice significantly increased the SOD, GR, nitrates, DA, and serotonin levels, and decreased the level of LPO when compared with scopolamine‐treated mice. Conclusion: These results indicate that EETP may exert anti‐amnesic effect through both by anti‐AChE and antioxidant mechanisms. Key words: Cognition, Morris water maze, passive avoidance, scopolamine, Tagetes patula, transfer latency