Melatonin Improves Learning and Memory Impairment in Chronic Stress Rats

This study aimed to observe the effect of melatonin on chronic stress rats. 60 male rats were randomly divided into five groups: control group (CON group), chronic stress group (CS group), melatonin high dose group (HMT group, 10mg/kg), melatonin middle dose group (MMT group, 5mg/kg), and melatonin low dose group (LMT group, 1mg/kg). Melatonin was daily intragastrically administrated for 4w with stress induction. Ability of spatial learning and memory of rats were determined by morris water maze. Concentration of Ca2+, contents of nitric oxide synthase (NOS) and nitric oxide (NO), and the number of CA3 neurons in hippocampus were tested. Compared with CON group rats, ability of learning and memory were significantly decreased, concentration of Ca2+ and contents of NOS and NO in the hippocampus were significantly increased in CS group rats. The number of CA3 neurons in hippocampus was decreased in CS group rats. As compared with CS group rats, ability of learning and memory were improved in MMT group and LMT group rats, and concentration of Ca2+, contents of NOS and NO in the hippocampus were significantly decreased, and the number of CA3 neurons was decreased in hippocampus. It shows that melatonin improving learning and memory impairment is likely by reducing the calcium and NO in hippocampus.