Lab Anim Res.  2018 Dec;34(4):239-247. 10.5625/lar.2018.34.4.239.

Bacopa monnieri extract improves novel object recognition, cell proliferation, neuroblast differentiation, brain-derived neurotrophic factor, and phosphorylation of cAMP response element-binding protein in the dentate gyrus

• Kwon HJ
• Jung HY
• Hahn KR
• Kim W
• Kim JW
• Yoo DY
• Yoon YS
• Hwang IK
• Kim DW

• KMID: 2459301
• DOI: http://doi.org/10.5625/lar.2018.34.4.239

Abstract

Bacopa monnieri is a medicinal plant with a long history of use in Ayurveda, especially in the treatment of poor memory and cognitive deficits. In the present study, we hypothesized that Bacopa monnieri extract (BME) can improve memory via increased cell proliferation and neuroblast differentiation in the dentate gyrus. BME was administered to 7-week-old mice once a day for 4 weeks and a novel object recognition memory test was performed. Thereafter, the mice were euthanized followed by immunohistochemistry analysis for Ki67, doublecortin (DCX), and phosphorylated cAMP response element-binding protein (CREB), and western blot analysis of brain-derived neurotrophic factor (BDNF). BME-treated mice showed moderate increases in the exploration of new objects when compared with that of familiar objects, leading to a significant higher discrimination index compared with vehicle-treated mice. Ki67 and DCX immunohistochemistry showed a facilitation of cell proliferation and neuroblast differentiation following the administration of BME in the dentate gyrus. In addition, administration of BME significantly elevated the BDNF protein expression in the hippocampal dentate gyrus, and increased CREB phosphorylation in the dentate gyrus. These data suggest that BME improves novel object recognition by increasing the cell proliferation and neuroblast differentiation in the dentate gyrus, and this may be closely related to elevated levels of BDNF and CREB phosphorylation in the dentate gyrus.

Keyword

Bacopa monnieri extract; dentate gyrus; novel object recognition; neurogenesis; brain-derived neurotrophic factor

MeSH Terms

Animals
Bacopa*
Blotting, Western
Brain-Derived Neurotrophic Factor*
Cell Proliferation*
Cognition Disorders
Cyclic AMP Response Element-Binding Protein*
Dentate Gyrus*
Discrimination (Psychology)
Immunohistochemistry
Memory
Mice
Neurogenesis
Phosphorylation*
Plants, Medicinal
Brain-Derived Neurotrophic Factor
Cyclic AMP Response Element-Binding Protein

Figure

• 

  Figure 1 Exploration time (n=10 per group) in training and testing trials, and discrimination index in the testing trial of familiar vs. new objects during the testing day of the novel object recognition test in control, vehicle-treated, and Bacopa monnieri extract (BME)-treated mice (n=10 per group; *P<0.05, vs. familiar object; aP<0.05, vs. control group; bP<0.05, vs. vehicle-treated group). All data are shown as % exploration time±SEM.

• 

  Figure 2 Ki67 immunohistochemistry in the dentate gyrus of control, vehicle-treated, and Bacopa monnieri extract (BME)-treated mice. Ki67-positive nuclei are most abundantly detected in the subgranular zone of dentate gyrus in BME-treated mice. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer. Scale bar=50 µm. The relative number of Ki67-positive nuclei in the dentate gyrus per section for each group are shown as a percentage of the value (n=5 per group; aP<0.05, vs. control group; bP<0.05, vs. vehicle-treated group). Data are presented as mean±SEM.

• 

  Figure 3 Immunohistochemistry for doublecortin (DCX) in the dentate gyrus of control, vehicle-treated, and Bacopa monnieri extract (BME)-treated mice. In the BME-treated group, DCX immunoreactive neuroblasts and their dendrites are most abundantly observed in the dentate gyrus. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer. Scale bar= 50 µm. The relative optical densities (RODs) expressed as a percentage of the value representing the DCX immunoreactivity in the dentate gyrus of the control group are shown. The number of DCX-immunoreactive neuroblasts in the dentate gyrus per section for each group are also shown (n=5 per group; aP<0.05, vs. control group; bP<0.05, vs. vehicle-treated group). Data are presented as mean±SEM.

• 

  Figure 4 Immunohistochemistry for phosphorylated cAMP response element-binding protein (pCREB) in the dentate gyrus of control, vehicle-treated, and Bacopa monnieri extract (BME)-treated mice. Strong and abundant pCREB-positive nuclei are observed in the subgranular zone in BME-treated mice. GCL, granule cell layer; ML, molecular layer; PL, polymorphic layer. Scale bar=50 µm. The relative number of pCREB-positive nuclei in the dentate gyrus per section for each group are shown as a percentage of the value (n=5 per group; aP<0.05, vs. control group; bP<0.05, vs. vehicle-treated group). Data are presented as mean±SEM.

• 

  Figure 5 Western blot analysis showing the percentage BDNF expression in hippocampal dentate gyrus of control, vehicle-treated, and Bacopa monnieri extract (BME)-treated groups (n=5 per group; aP<0.05, vs. control group; bP<0.05, vs. vehicle-treated group). Data are presented as mean±SEM.

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