Abstract
Problem statement: Demand for cognitive-enhancing drugs is growing. Numerous medicinal plants possessing antioxidant activity have received much attention as food supplement to improve cognitive function. Quercetin is a potent free radical scavenger and antioxidant. However, the limitations of quercetin: Rapidly metabolized is an obstacle to its use for a cognitive enhancer. In addition, the burden of blood brain barrier can be overcome by nasal administration and liposomes. In the present study, we investigated whether nasal administration of quercetin liposomes could improve spatial memory in healthy adult rats. Approach: Male Wistar rats were pretreated with quercetin liposomes, containing 0.5 mg of quercetin in 20 µL (dose = 20 µg), via right nasal cavity once daily continually for 4 weeks. Evaluation of rodent learning and memory was assessed by Morris water maze test and then all rats were sacrificed for determining the survival and cholinergic neurons densities in hippocampus. Results: Quercetin liposomes via nasal route treated rats exhibited a significant improvement in cognitive performance. In addition, nasal administration of quercetin liposomes also resulted in induced the densities of survival and cholinergic neurons in hippocampus. However, further researches about the precise underlying mechanism are still required. Conclusion: Our studies demonstrate that quercetin liposomes via nasal administration may have a candidate for cognitive enhancer in the future.
Highlights
Memory is a complex process requiring the coordination of many different regions of brain and many neurotransmitter systems
The results showed that the spontaneous behavior as mention earlier did not differ significantly between the control, vehicle (PEG), free liposomes treated group and quercetin liposomes throughout the experimental period
Effect of quercetin liposomes on spatial memory: Hippocampus-dependent spatial memory was assessed with the Morris water maze test
Summary
Memory is a complex process requiring the coordination of many different regions of brain and many neurotransmitter systems. Among the various neurotransmitter systems, the cholinergic system has attracted special attention because lesions leading to loss of cholinergic neurons in the basal forebrain can cause defects of memory (Leanza et al, 1996; Zhang et al, 1996), muscarinic acetylcholine receptor antagonists when given to animals can induce memory deficit (Introini-Collison and McGaugh, 1988) and agonists (Schwarz et al, 1999) as well as cholinesterase inhibitors (Lyketsos et al, 2004) when given to memory impaired animals or dementia patients can improve the memory. Many studies have suggested that reversals in age-related memory declines might be accomplished by increasing the dietary intake possessing high antioxidant activity (Youdim et al, 2002; Andres-Lacueva et al, 2005; Jabeen et al, 2007) and this reversal effect has been claimed to be associated with the antioxidant activity (Raghavendra and Kulkarni, 2001). A large list of herbal extracts possessing high antioxidant activity and improve memory is available in the market
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