Promotion of neuronal differentiation through activation of N‐methyl‐D‐aspartate receptors transiently expressed by undifferentiated neural progenitor cells in fetal rat neocortex

Abstract

Neural progenitor cell is a generic term for undifferentiated cell populations composed of neural stem, neuronal progenitor, and glial progenitor cells with abilities for self-renewal and multipotentiality. In this study, we have attempted to evaluate the possible functional expression of N-methyl-D-aspartate (NMDA) receptors by neural progenitor cells prepared from neocortex of 18-day-old embryonic rats. Cells were cultured in the presence of basic fibroblast growth factor (bFGF) for different periods up to 12 days under floating conditions. Reverse transcription-polymerase chain reaction and fluorescence imaging analyses revealed transient expression of functional NMDA receptors in neurospheres formed by clustered progenitors during the culture with bFGF. A similarly potent increase was seen in the fluorescence intensity after brief exposure to NMDA in cells differentiated after the removal of bFGF under adherent conditions, and an NMDA receptor antagonist invariably prevented these increases by NMDA. Moreover, sustained exposure to NMDA not only inhibited the formation of neurospheres when exposed for 10 days from day 2 to day 12 but also promoted spontaneous and induced differentiation of neurospheres to cells immunoreactive for a neuronal marker protein on immunocytochemistry and Western blotting analyses. These results suggest that functional NMDA receptors may be transiently expressed to play a role in mechanisms underlying the modulation of proliferation along with the determination of subsequent differentiation fate toward a neuronal lineage in neural progenitor cells of developing rat neocortex.

Neurogenesis Mediated by γ-Aminobutyric Acid and Glutamate Signaling

“…In the rat neocortical lower cell layer before culture, mRNA expression was seen for NR1, NR2A-2C, and NR2D subunits of the NMDAR subtype; GluR1 -4 subunits of the AMPAR subtype; and GluR5, GluR6, GluR7, KA1, and KA2 subunits of the KAR subtype on RT-PCR analysis (57). In neocortical neurospheres cultured for 12 days, mRNA expression was similarly seen for NR2A-2C subunits of NMDAR; GluR1 -4 subunits of AMPAR; and GluR5, GluR6, KA1, and KA2 subunits of KAR, but not for NR1 and NR2D subunits of NMDAR and the GluR7 subunit of KAR.…”

Neural stem cells: mechanisms and modeling

“…Evidence based on cultured NSCs supports the finding that nNOS gene expression is involved in the feedback modulation of NSC differentiation by NMDARs (Hu et al, 2008). Interestingly, several other studies using NSC cultures have suggested that NMDA activation could promote the neuronal fate determination of NSCs (Deisseroth et al, 2004;Kitayama et al, 2004;Yoneyama et al, 2008). Hence, the differentiation and proliferation of NSCs is likely subtly regulated by activity within a range; too-high or too-low levels of neuronal activity can both delay the process of neurogenesis.…”

Glycine transporter-1 regulates the proliferation of neural stem/progenitor cells derived from the embryonic mouse hippocampus

“…extracellular glycine is effectively increased by blocking GLYT1 and that this mediates synaptic integration by dual activation of both the glycine receptor and the NMDA receptor [20,21]. Numerous previous studies have shown that proliferation of NPCs is regulated by activation of various receptors and these neurotransmitters; i.e., activation of the GABAA receptor, group I metabotropic glutamate (mGlu) receptor or dopamine D 3 receptor enhances proliferation of NPCs [22][23][24], whereas activation of the NMDA receptor, group III mGlu receptor, or α4β2 nicotinic acetylcholine receptor suppresses proliferative activity [25][26][27][28].…”