RESUMO
N-methyl-D-aspartate receptors (NMDARs) are known to play critical roles in the development of the nervous system, and their expression is regulated in an activity-dependent fashion during development. However, the regulation of NMDAR expression after circuit formation is less well understood. To examine this, we performed patch-clamp recordings from chick cerebral neurons in an activity-controlled culture. Analysis of NMDAR channels from neurons before synapse formation showed that there are two components in channel open kinetics. The major slow component is clearly blocked by ifenprodil, a specific inhibitor of NR2B-containing NMDARs. In contrast, slow component of NMDAR channel opening from neurons after synapse formation became minor and ifenprodil had little effect on the NMDAR channel openings. Furthermore, this change is reversibly regulated by neuronal activity, in that suppression induces the re-expression of NR2B-containing NMDARs, even after circuit formation.
Assuntos
Potenciais de Ação/fisiologia , Inibição Neural/fisiologia , Neurônios/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Transmissão Sináptica/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Células Cultivadas , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/crescimento & desenvolvimento , Embrião de Galinha , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Inibição Neural/efeitos dos fármacos , Vias Neurais/citologia , Vias Neurais/efeitos dos fármacos , Vias Neurais/crescimento & desenvolvimento , Neurônios/efeitos dos fármacos , Piperidinas/farmacologia , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Bloqueadores dos Canais de Sódio/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Tetrodotoxina/farmacologiaRESUMO
Although a subpopulation of mRNAs has been identified as translocated to the dendrites or the synaptic regions of neurons, the translocational mechanism has not been elucidated. To find mRNAs enriched in synapses, we compared the synaptosomal mRNAs with those from whole forebrain using differential display (DD). We cloned one of these mRNAs, which encoded a novel 31 kDa protein (PMES-2). PMES-2 mRNA was specifically transcribed in the brain and was present in the dendrites of the hippocampal neurons. PMES-2 protein was partly localized in the postsynaptic density. Although this protein is very similar to human NABC1 protein, its function is still unknown.