Entacapone promotes hippocampal neurogenesis in mice

Entacapone,a catechol-O-methyltransferase inhibitor,can strengthen the therapeutic effects of levodopa on the treatment of Parkinson’s disease.However,few studies are reported on whether entacapone can affect hippocampal neurogenesis in mice.To investigate the effects of entacapone,a modulator of dopamine,on proliferating cells and immature neurons in the mouse hippocampal dentate gyrus,60 mice(7 weeks old)were randomly divided into a vehicle-treated group and the groups treated with 10,50,or 200 mg/kg entacapone.The results showed that 50 and 200 mg/kg entacapone increased the exploration time for novel object recognition.Immunohistochemical staining results revealed that after entacapone treatment,the numbers of Ki67-positive proliferating cells,doublecortin-positive immature neurons,and phosphorylated cAMP response element-binding protein(pCREB)-positive cells were significantly increased.Western blot analysis results revealed that treatment with tyrosine kinase receptor B(TrkB)receptor antagonist significantly decreased the exploration time for novel object recognition and inhibited the expression of phosphorylated TrkB and brain-derived neurotrophic factor(BDNF).Entacapone treatment antagonized the effects of TrkB receptor antagonist.These results suggest that entacapone treatment promoted hippocampal neurogenesis and improved memory function through activating the BDNF-TrkB-pCREB pathway.This study was approved by the Institutional Animal Care and Use Committee of Seoul National University(approval No.SNU-130730-1)on February 24,2014.

Activation of glycine site and GluN2B subunit of NMDA receptors is necessary for ERK/CREB signaling cascade in rostral anterior cingulate cortex in rats:Implications for affective pain

Objective The rostral anterior cingulate cortex （rACC） is implicated in processing the emotional component of pain. N-methyl-D-aspartate receptors （NMDARs） are highly expressed in the rACC and mediate painrelated affect by activating a signaling pathway that involves cyclic adenosine monophosphate （cAMP）/protein ki- nase A （PKA） and/or extracellular regulated kinase （ERK）/cAMP-response element-binding protein （CREB）. The present study investigated the contributions of the NMDAR glycine site and GluN2B subunit to the activation of ERK and CREB both in vitro and in vivo in rat rACC. Methods Immunohistochemistry and Western blot analy- sis were used to separately assess the expression of phospho-ERK （pERK） and phospho-CREB （pCREB） in vitro and in vivo. Double immunostaining was also used to determine the colocalization of pERK and pCREB. Results Both bath application of NMDA in brain slices in vitro and intraplantar injection of formalin into the rat hindpaw in vivo induced significant up-regulation of pERK and pCREB in the rACC, which was inhibited by the NMDAR antago- nist DL-2-amino-5-phospho-novaleric acid. Selective blockade of the NMDAR GluN2B subunit and the glycine- binding site, or degradation of endogenous D-serine, a co-agonist for the glycine site, significantly decreased the up- regulation of pERK and pCREB expression in the rACC. Further, the activated ERK predominantly colocalized with CREB. Conclusion Either the glycine site or the GluN2B subunit of NMDARs participates in the phosphorylation of ERK and CREB induced by bath application of NMDA in brain slices or hindpaw injection of 5% formalin in rats, and these might be fundamental molecular mechanisms underlying pain affect.