Neurons generated from adult rat hippocampal stem cells form functional glutamatergic and GABAergic synapses in vitro

Basic fibroblast growth factor-responsive neural stem cells (NSCs) derived from adult rat hippocampus were earlier demonstrated to generate neurons an d glia. These stem-cell-derived neurons express GABA, acetylcholinesterase, tyrosine hydroxylase, or calbindin. It has not been clear, however, whethe r or not these stem-cell-derived neurons are able to form functional synaps es. In the present study, we investigated the development of synapse format ion by adult hippocampus-derived neural stem cells. NSCs from adult rat hip pocampi and primary embryonic rat hippocampal neurons were cocultured on a glial feeder layer. Immunofluorescence studies revealed that some of the NS Cs became immunoreactive for microtubule-associated protein 2ab, neurofilam ent 200, synaptobrevin, or synaptophysin. These cells possessed properties of functional neurons such as action potentials and miniature postsynaptic currents (mPSCs). The elicited mPSCs with rapid kinetics were blocked by 6, 7-dinitroquinoxaline-2,3-dione (DNQX), but not by bicuculline (excitatory m PSCs). The remaining mPSCs had slower kinetics and were blocked by bicucull ine, but not by DNQX (inhibitory mPSCs). We considered that the neurons der ived from the adult NSCs expressed both non-NMDA glutamate receptors and th e GABA(A) receptors and formed functional synapses. Our results demonstrate that adult NSCs can differentiate into neurons with functional glutamaterg ic and GABAergic synaptic transmission in vitro and support the concept tha t such neurons could integrate into the neuronal circuitry. (C) 2000 Academ ic Press.