Neuroprotective effect of Celastrus paniculatus on chronic stress-induced cognitive impairment

Discussion

The current study intended to assess the beneficial effect of CPoil treatment on spatial learning and memory and anxiety in chronically stressed rats. We showed that chronic restraint stress for 21 days resulted in impaired spatial learning and memory in RAM task. Furthermore, stressed animals exhibited working memory impairment in T-maze task. Chronic stress resulted in enhanced anxiety-like behavior in the EPM. The data are in consistent with the previous studies suggesting compromised memory functions and enhanced anxiety in chronic stress models.[3,4,5,6]

Interestingly, chronic treatment with CP oil for 14 days reversed stress-induced spatial learning and memory impairment in RAM task as shown by enhanced percentage correct choices and reduced RMEs. Working memory is also restored back to normal after CP oil treatment. CP oil showed anxiolytic action in this chronic stress model by increasing number of entries and time spent in the open arms of EPM. Interestingly, vehicle treatment to stressed rats did not show any improvement in spatial learning, working memory, and anxiety behavior. This confirms the beneficial effect of CP on stress-induced cognitive deficits.

The precise mechanism responsible for beneficial effects of CP oil against chronic stress-induced cognitive dysfunctions is not known, but it may be due to its antioxidant and neuroprotective effects.[10,18,19] Previous studies examined the effects of CP on learning and memory in different behavioral tasks.[12,20,21] When tested in a raised platform shock-avoidance task, CP-treated group (400 mg/kg once daily for 3 days) displayed a significantly improved learning compared to vehicle control group.[20] Another study by Nalini et al. reported that CP oil treatment for 15 days (850 mg/kg once daily) enhanced retention in passive avoidance task.[21] In addition, previous study from our laboratory demonstrated cognitive-enhancing effect of CP in naive animals.[12] Hence, the current study is consistent with previous studies with regard to the ability of CP in augmenting cognitive performance in different memory tasks.

Methanolic extract of CPshowed a dose-dependent free radical scavenging action and a protective effect on H2O2-induced cytotoxicity and DNA damage in human nonimmortalized fibroblasts.[22] Furthermore, CP water extracts protected cultured forebrain neuronal cells by reducing lipid peroxidation and enhancing the antioxidant enzyme catalase activity.[18] CP water extract showed neuroprotective action against glutamate-induced toxicity in neuronal cultures and reversibly inhibited N-methyl-D-aspartate-activated whole currents.[19] Previous study has shown cognitive-enhancing efficacy of CP in normal animals.[12] An improvement in learning and memory in both the shuttle box and step-through paradigm was seen after aqueous seed extract of CP.[23] Chronic oral administration of CP seed oil (50, 200, or 400 mg/kg) for 14 days completely reversed the scopolamine (0.5 mg/kg)-induced learning deficits.[21,13]

Tham khảo  Cultivated Garlic

Previous studies demonstrated the anti-anxiety activity of CP. The petroleum ether extract of seeds showed anti-anxiety activity by significantly reduced punishment and reward associated inhibition of operant behavior in rats at different doses.[24] CP oil exhibited significant anxiolytic activity in the EPM and thirsty rat conflict paradigm.[24,25] Further, CP did not produce any sedative effect and reversed anxiolytic effect of 5-HT1A partial agonist buspirone in the open-field test, indicating its effect on serotonergic neurotransmission.[25]