Effect of astaxanthin on short-term memory and levels of acetylcholinesterase (AChe) and mitochondrial complex 1 in scopolamine treated mice

Alzheimer's disease (AD) is a neurological disorder that eventually will cause memory loss and cognitive decline. To date, there is no pure treatment to cure AD. Current medication of AD can temporarily slow down Alzheimer's symptoms and improve the quality of life of patients but still show a lot of side effects. Astaxanthin was used in this study as it has antioxidants property. This study was performed to evaluate the effectiveness of astaxanthin in short-term memory and levels of acetylcholinesterase (AChE) and mitochondrial complex 1 in mice. Twenty-five mice were divided into five groups; control group, memory deficit group (MDG), group 1, group 2 and group 3. Mice in MDG, group 1, 2 and 3 were injected with 3mg/kg of scopolarnine once daily through intraperitoneally (i.p.) for 28 days. However, on day 22, mice in group 1, 2 and 3 were administered with incremental dosage of astaxanthin that is 12.5, 25 and 50 mg/kg respectively for 7 days. The administration of astaxanthin was given once daily and orally (p.o.). In addition, mice in control group were administered with 0.5ml/100g of 0.9% normal saline once daily via intraperitoneally (i.p.) for 28 days. The short-term memory was tested in behavioural test by using Morris Water Maze (MWM). Meanwhile, test on levels of acetylcholinesterase (AChE) and mitochondrial complex 1 were tested in laboratory. In behavioural test, the effect of 3mg/kg of Scopolamine showed an increase in total distance travelled by the mice especially in MDG on day 1 to 21. On day 22 to 28, mice in astaxanthin-treated group showed a gradually decrease in total distance travelled compared to MDG. The shortest total distance travelled among these three astaxanthin-treated groups were shown in mice in group 3 (50mg/kg astaxanthin). Meanwhile, the level of AChE in MDG was higher compared to control group. In comparison of mice in astaxanthin-treated group and MDG, mice in group 3 showed lower level of acetylcholinesterase compared to MDG. Lastly, in mitochondrial Complex 1 test, mice in MDG showed lower level of free radicals reduction at Complex 1 compared to control group. Meanwhile, mice in group 3 which were administered with 50mg/kg astaxanthin, showed higher level of free radicals reduction at Complex 1 compared to MDG. The rest showed no difference.