Takeuchi ( 1 ) 〔 r ' ノ ) ln. fi ' tilrltc ' of lndtt . yrriai Science , The VniversitJ / qf τok . yo ) 、 yee ITP4 −Ol N − methy1 − D − aspartate receptors 〔 NMDARs ) Looated in Lh巳 posLsynapti じ mcmbrane in the s } 「 napse exchange with Lllosc located eutside the synase , providing imp〔,rtallt means fDr regulating the efficacy 〔 } f synaptic transmission . However 、 the mechanislns for the excllange and the outside pool of NMDARs havc not been understood . NMDARs in tle synapsc might exchange

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... 山 those in the plasma membran 巳 wilhin a sccond by latera 且diffusion ( Groc 巳t aL , 2006) . or wi しh the unkllown じytoplasmic pool in minules ( Sharma じt al. , 2006). Here, we examined the dynaniics oll YFP −NMDAR express . ed Ln hippocampal neurons . ( 1) Single− molecu 且 e tracking of NMDAR showed it-diffus . ion outside the synapse , wi 出 imermitしellt tenlporary 亡rapping at dle rece ρ tor cluslers . ( 2 ) In poin亡 一 TIRF − FRAP experilnents using a diffraction limjLcd spot of −l miGrons in diamcter , bleaching a singie in山 vidual NMDAR cluster aL a Limc , the mobile f『action represcntcd − 4090 and 声 20% with a ha げ 一 reco ・ ery time o1 ' 一 ・ 2 min alld −・ 3min in younger ( 7 − daン old) and 〔 )ld じr ( 21 − day old ) neu 【 ・ ons , sllowing 山 at exchanges eccur more s工 ow . ly as neurons mature . ( 3)Arcal TIRF − FRAP experiments , wherc an 訂 ca ol ' ・ −20 microns in diameter was bleached, practically gave thc same result as the poin トEpi −FRAP exanlinations . These results indicate that extcnsive cxchanges occur with the Gytoplasmic pool via ondocyk } sis −exoeytosis tlat occurs near or at thc synapse , and suggest that lateral diffusion of NMDAR ± ' acilitates the trafftc between the synapse and the membranc insertion / internalization siLes .