Alterations in synaptic pasticity caused by St. John's wort may mitigate negative effects of stress on spatial working memory
St. John’s wort (Hypericum perforatum) is one of the popular herbal drugs in Europe and USA. We have recently described benefi cial effects of this herb in the treatment of stress-evoked memory impairments. The aim of the present study was to test a hypothesis that St. John’s wort alleviates stress- and corticosterone-related memory impairments by restoring levels of synaptic plasticity proteins: neuromoduline (GAP-43) and synaptophysin (SYP) in hippocampus and prefrontal cortex. Stressed and corticosterone treated rats presented a signifi cantly delayed acquisition of spatial working memory (P<0.001) in the Barnes maze (BM). Chronic administration of H. perforatum (350 mg kg-1 for 21 days) potently and signifi cantly improved processing of spatial information in the stressed and corticosterone treated rats (P<0.001). Also the herb increased levels of GAP-43 and SYP, in both St. John’s wort treated rat’s hippocampus (P<0.05 and P>0.05, respectively) and prefrontal cortex (P<0.05 and P<0.05) as measured by western immunoblotting. We found that H. perforatum prevented the deleterious effects of both chronic restraint stress and prolonged corticosterone treatment on working memory measured in BM test. These fi ndings indicate that at least part of the benefi cial effect of H. perforatum on memory may be mediated by GAP-43 and SYP proteins.