Cod liver oil (CLO) is a rich source of omega-3 fatty acids (FA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The existing data suggest that EPA and DHA are the active agents of fish oil. In this study, we tested a hypothesis that the active constituents of CLO alleviate the negative impact of prolonged restraint stress on cognitive functions of male Wistar rats. Specifically, we attempted to characterize the preventive action of long-lasting treatment with CLO [0.375 ml/100 g body weight (equivalent to a dose of 300 mg/kg DHA and 225 mg/kg EPA), p.o. for 21 days] against an impairment caused by chronic restraint stress (2 h daily for 21 days) on recall as tested in a passive avoidance situation and on the spatial reference and working memory tested in a Barnes maze as well as on locomotor activity and anxiety behavior tested respectively in an open field and elevated plus-maze. We found that CLO administration statistically significantly (p < 0.01, both) prevented the deleterious effects of chronic restraint stress on recall and the spatial memory.
It is recognized that chronic stress is an important risk factor for the development of several cognitive impairments involving working memory. Working memory refers to the memory in which the information to be remembered changes from trial-to-trial and should be assessed in a task able to detect retrieval of that information. In the present study, we tested the hypothesis that preventive administration of Hypericum perforatum (also named St John's wort) may counteract the working memory impairments caused by repeated stress. Specifically, we attempted to characterize the preventive action of long-lasting treatment with St John's wort (350 mg/kg, p.o.) on the spatial working memory impairments caused by chronic restraint stress (2 h daily for 21 days) or durable medication with exogenous corticosterone (5 mg/kg, s.c.) in male Wistar rats. Spatial working memory was tested in Barnes maze (BM) and in the Morris water maze (MWM). We found that H. perforatum prevented the deleterious effects of both chronic restraint stress and prolonged corticosterone on working memory measured in both tests. The herb significantly improved hippocampus dependent spatial working memory in comparison with control (p < 0.01) and alleviated some other negative effects of stress on cognitive functions.
St. John's wort (Hypericum perforatum) is one of the leading psychotherapeutic phytomedicines. Beneficial effects of this herb in the treatment of mild to moderate depression are well known. In this study we tested a hypothesis that St. John's wort alleviates age-related memory impairments by increasing the levels of cyclic adenosine 3', 5'-monophosphate response element binding protein (CREB) and phosphorylated CREB (pCREB) in hippocampus. Middleaged rats (18 month-old) displayed a decline in the acquisition of spatial working memory (p < 0.001) in the Morris water maze (MWM). Chronic administration of Hypericum perforatum (HP) (350 mg/kg for 21 days), potently and significantly improved the processing of spatial information in the aged rats (p < 0.001). Also the herb increased the levels of pCREB in the aged rat's hippocampus (p < 0.01) as measured by western immunoblotting. Aging caused significant locomotor impairments as tested in the open field (p < 0.001) but not in the MWM test. However, these were unaffected by treatment with HP. Thus, this study indicates that St. John's wort effectively prevents aging-induced deterioration of spatial memory in 18 month-old rats, possibly by the activation of CREB regulated genes associated with memory formation. It appears that mechanism is probably inactive in young rats.
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