Experience-Dependent Formation and Recruitment of Large Vesicles from Reserve Pool

Abstract

The sizes and contents of transmitter-filled vesicles have been shown to vary depending on experimental manipulations resulting in altered quantal sizes. However, whether such a presynaptic regulation of quantal size can be induced under physiological conditions as a potential alternative mechanism to alter the strength of synaptic transmission is unknown. Here we show that presynaptic vesicles of glutamatergic synapses of Drosophila neuromuscular junctions increase in size as a result of high natural crawling activities of larvae, leading to larger quantal sizes and enhanced evoked synaptic transmission. We further show that these larger vesicles are formed during a period of enhanced replenishment of the reserve pool of vesicles, from which they are recruited via a PKA- and actin-dependent mechanism. Our results demonstrate that natural behavior can induce the formation, recruitment, and release of larger vesicles in an experience-dependent manner and hence provide evidence for an additional mechanism of synaptic potentiation.

Activity-dependent retrograde laminin A signaling regulates synapse growth at Drosophila neuromuscular junctions

“…Larvae stayed in food without much crawling but were highly motile when food was deprived. Within 2 h of deprivation, the NMJ size remained the same, as previously reported (18). With 8-h food deprivation, the NMJ size was enlarged significantly (Fig.…”

“…Higher crawling activity can be induced by rearing larvae at higher temperatures or in starvation, leading to larger dimensions of NMJs with more terminal branches and synaptic boutons (18)(19)(20). Whereas the NMJ morphology showed no difference in larvae reared at 17, 22, 25, and 27°C ( Fig.…”

Wnt Signaling in Neuromuscular Junction Development

“…In addition, larval NMJs undergo structural and functional modifications in response to experience and electrical activity (Budnik et al 1990;Sigrist et al 2003;Steinert et al 2006;Ataman et al 2008;Koon et al 2011), offering a powerful experimental system to study the molecular processes underlying synaptic growth and plasticity.…”

Temperature-Dependent Developmental Plasticity ofDrosophilaNeurons: Cell-Autonomous Roles of Membrane Excitability, Ca2+Influx, and cAMP Signaling

“…These temperature effects seem to be mediated by an increase in presynaptic excitability (Zhong and Wu, 2004), reminiscent of the enhanced motor axon ramification in hyperexcitable K ϩ channel mutants (Budnik et al, 1990;Zhong et al, 1992). However, at elevated temperatures, enhanced neuronal growth may result from trophic interaction involving both central pattern generator activity and muscle contraction (Sigrist et al, 2003;Steinert et al, 2006). Hence, it is important to delineate cellautonomous components from those requiring cell-cell interactions in temperature-dependent neuronal plasticity.…”