抄録
Activity-dependent internalization of glutamate receptor (GluR) is an underlying mechanism for the long-term depression (LTD) of synaptic efficacy at synapse between the parallel fiber (PF)-Purkinje cell (PC) in the cerebellum. However, translocation of AMPA-receptor at the dendritic spine has not been examined by image-analysis in PC. Here, we visualize activity-dependent change in AMPA-R distribution by using a monoclonal antibody recognizing extracellular domain of GluR2 and GFP-labeled GluR2 in cultured PC. Surface-expression of GluR2, detected by the monoclonal antibody, was dense at the dendritic spines. Chemical stimulation (40μM Glu+40mM KCl) caused internalization of GluR2, which was enhanced by latrunculin A, a blocker of actin-polymerization, while it was suppressed by jasplakinolide, a blocker of actin-depolymerization. These observations suggest that actin-depolymerization underlies the induction of the activity-dependent GluR2-internalization. Then, we analyzed time-dependent change in the spine-shape and GluR2-distribution in dendrite. Chemical stimulation (Glu+KCl) caused persistent retraction of GFP-GluR2 from the surface of dendritic spines, but the length of spines, visualized by GFP, was shortened by the same stimulation only temporally. Thus, we conclude that LTD-inducing chemical stimulation (Glu+KCl) causes release of GluR2 from F-actin-based scaffolds and translocation of them from synaptic membrane to the intracellular storage site in the dendritic shaft of PC. [J Physiol Sci. 2008;58 Suppl:S126]
