シナプス前部・後部構造の形態変化の同時観察

抄録

Dendritic spines are highly motile structures, but how spines move while keeping their contacts with presynaptic varicosities is not clear. To analyze movements of these synaptic structures simultaneously, we labeled CA1 pyramidal cells with green fluorescent protein and CA3 pyramidal cells with rhodamine-dextran in hippocampal slice cultures. We obtained stable expression of GFP in a limited population of CA1 pyramidal neurons by using transgenic mice with a Cre-loxP recombination system. CA3 pyramidal neurons of the slice cultures were loaded with rhodamine-dextran by electroporation. Labeled varicosities of CA3 pyramidal cells and spines of CA1 pyramidal cells were visualized using two-photon microscopy to detect close association of the two components. Time-lapse imaging revealed that they performed rapid morphological changes without losing their contacts. The extent of overall structural changes between varicosities and spines was correlated, while the direction of short-term volume changes was regulated independently. Furthermore, dendritic morphological changes induced by electrical stimulation had little effect on their association. These results suggest that synaptic junctions provide stable attachment sites functioning to correlate presynaptic and postsynaptic motility. [J Physiol Sci. 2006;56 Suppl:S30]