ABSTRACT Rehmannia glutinosa is a traditional Chinese medical herb and has a long history in cognitive deficits therapy. Its ther-apeutic efficacy has been confirmed by clinical studies. In this study, we attempted to investigate the effects of catalpol, an iridoid from Rehmannia glutinosa, on cognitive and behavioral function of aged rats with memory loss. 22 - 24 month Sprague-Dawley spontaneous rats of memory loss with aging were selected by step-down type passive avoidance test and randomly allocated to two groups: the aged rats with memory loss (control group) and the catal- pol-treated (5 mg/kg) group. We performed open-field and Y-maze test to evaluate special performance and behavior response before and after catalpol treatment for 5 and 10 days. Growth-associated protein (GAP-43) in hippocampus and frontal cortex was measured using immunohistochemistry and quantitative Western Blotting. The results showed that catalpol could significantly improve not only spatial learning and memory but also locomotor activity and ex-plora- tory behavior of aged rats with memory loss. GAP-43 protein in hippocampal CA3 region and dentate granule of catal- pol-treated rats was significantly enhanced than that of control group. Western blot analysis demonstrated a catal- pol-associated increase of GAP-43 in hippocampus of catalpol-treated rats and correlated with spatial memory, loco- motor activity and exploratory behavior. However, there was no difference in GAP-43 protein in frontal cortex between two groups. These results indicated that catalpol could enhance spatial performance and behavioral responses in aged rats with memory loss, and the mechanism may involve up-regulation of GAP-43 level of hippocampus in the brain. It also suggested that catalpol may be a useful natural drug for Alzheimer’s disease (AD) treatment by modulating hippo- campal neuroplasticity.
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