A vesicle superpool spans multiple presynaptic terminals in hippocampal neurons.
Bottom Line: Here, we demonstrate a vesicle pool that is not confined to a synapse but spans multiple terminals.In acute hippocampal slices we show that the mobile vesicle pool is also a feature of native brain tissue.We also demonstrate that superpool vesicles are available to synapses during stimulation, providing an extension of the classical recycling pool.
Affiliation: School of Life Sciences, University of Sussex, Brighton, UK. email@example.comShow MeSH
Related in: MedlinePlus
Mentions: To date, the characterization of intersynaptic vesicle movement has been limited to work in cultured neurons (Chen et al., 2008; Darcy et al., 2006a; Fernandez-Alfonso and Ryan, 2008; Krueger et al., 2003; Westphal et al., 2008), and the relevance of this phenomenon to presynaptic organization in native tissue remains unclear. We addressed this question in acute hippocampal slices using two-photon microscopy to image presynaptic terminals labeled with FM1-43. After dye-loading, we observed discrete fluorescent puncta corresponding to presynaptic terminals in region CA1 as reported previously (Zakharenko et al., 2001) (Figure 3A). These labeled terminals were release competent because their fluorescence destained upon stimulation (Figure 3B). Axonal regions between stable puncta showed bidirectional trafficking of many fluorescent packets, large and small, with both merging and shedding events (Figures 3C and 3D), analogous to vesicle movement in culture (Figure S1) (Darcy et al., 2006a). To quantify vesicle flux at stable synapses, we monitored changes in fluorescence levels of single terminals over time. The cumulative fluorescence change corrected for imaging noise shows a linear profile (n = 39: Figure 3E), indicating that at most synapses fluorescence intensity fluctuates continuously, implying a constant vesicle flux through terminals. Our findings strongly support the idea that a shared pool of functional vesicles is a feature of native hippocampal tissue.
Affiliation: School of Life Sciences, University of Sussex, Brighton, UK. firstname.lastname@example.org