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We previously demonstrated that Bacopa monnier (L.) WETTST. extract (BME) ameliorated cognitive dysfunction in animal models of dementia by enhancing synaptic plasticity-related signaling in the hippocampus and protecting cholinergic neurons in the medial septum. To further clarify the pharmacological features and availability of BME as a novel anti-dementia agent, we investigated whether BME affects neuronal repair using a mouse model of trimethyltin (TMT)-induced neuronal loss/self-repair in the hippocampus. Mice pretreated with TMT (2.8 mg/kg, intraperitoneally (i.p.)) on day 0 were given BME (50 mg/kg, per os (p.o.)) once daily for 15-30 d. Cognitive performance of the animals was elucidated twice by the object location test and modified Y maze test on days 17-20 (Phase I) and days 32-35 (Phase II) or by the passive avoidance test on Phase II. TMT impaired hippocampus-dependent spatial working memory and amygdala-dependent fear-motivated memory. The administration of BME significantly prevented TMT-induced cognitive deficits. The protective effects of BME on the spatial memory deficits were confirmed by Nissl staining of hippocampal tissues and propidium iodide staining of organotypic hippocampal slice cultures. Immunohistochemical studies conducted on days 17 and 32 revealed that thirty days of treatment with BME increased the number of 5-bromo-2′-deoxyuridine (BrdU)-immunopositive cells in the dentate gyrus region of TMT-treated mice, whereas fifteen days of treatment with BME had no effect. These results suggest that BME ameliorates TMT-induced cognition dysfunction mainly via protecting the hippocampal neurons from TMT-induced hippocampal lesions and partly via promoting neuroregeneration in the dentate gyrus regions.

Bacopa monnieri L. Wettst. (BM) is a botanical component of Ayurvedic medicines and of dietary supplements used worldwide for cognitive health and function. We previously reported that administration of BM alcoholic extract (BME) prevents trimethyltin (TMT)-induced cognitive deficits and hippocampal cell damage and promotes TMT-induced hippocampal neurogenesis. In this study, we demonstrate that administration of BME improves spatial working memory in adolescent (5-week- old) healthy mice but not adult (8-week-old) mice. Moreover, improved spatial working memory was retained even at 4 weeks after terminating 1-week treatment of adolescent mice. One-week BME treatment of adolescent mice significantly enhanced hippocampal BrdU incorporation and expression of genes involved in neurogenesis determined by RNAseq analysis. Cell death, as detected by histochemistry, appeared not to be significant. A significant increase in neurogenesis was observed in the dentate gyrus region 4 weeks after terminating 1-week treatment of adolescent mice with BME. Bacopaside I, an active component of BME, promoted the proliferation of neural progenitor cells in vitro in a concentration-dependent manner via the facilitation of the Akt and ERK1/2 signaling. These results suggest that BME enhances spatial working memory in healthy adolescent mice by promoting hippocampal neurogenesis and that the effects of BME are due, in significant amounts, to bacopaside I.

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This study aimed to clarify the antidementia effects of ethanolic extract of Ocimum sanctum Linn. (OS) and its underlying mechanisms using olfactory bulbectomized (OBX) mice. OBX mice were treated daily with OS or a reference drug, donepezil (DNP). Spatial and nonspatial working memory performance was measured using a modified Y maze test and a novel object recognition test, respectively. Brain tissues of the animals were subjected to histochemical and neurochemical analysis. OS treatment attenuated OBX-induced impairment of spatial and nonspatial working memories. OBX induced degeneration of septal cholinergic neurons, enlargement of the lateral ventricles, and suppression of hippocampal neurogenesis. OS and DNP treatment also depressed these histological damages. OS administration reduced ex vivo activity of acetylcholinesterase in the brain. OBX diminished the expression levels of genes coding vascular endothelial growth factor (VEGF) and VEGF receptor type 2 (VEGFR2). Treatment with OS and DNP reversed OBX-induced decrease in VEGF gene and protein expression levels without affecting the expression of the VEGFR2 gene. These results demonstrate that the administration of OS can lessen the cognitive deficits and neurohistological damages of OBX and that these actions are, at least in part, mediated by the enhancement of central cholinergic systems and VEGF expression.

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