Data for: A synapse-specific refractory period for plasticity at individual dendritic spines

How newly formed memories are preserved while brain plasticity is ongoing
has been a source of debate. One idea is that synapses which experienced
recent plasticity become resistant to further plasticity, a type of
metaplasticity often referred to as saturation. Here, we probe the local
dendritic mechanisms that limit plasticity at recently potentiated
synapses. We show that recently potentiated individual synapses exhibit a
synapse-specific refractory period for further potentiation. We further
found that the refractory period is associated with reduced postsynaptic
CaMKII signaling; however, stronger synaptic activation fully restored
CaMKII signaling but only partially restored the ability for further
plasticity. Importantly, the refractory period is released after one hour,
a timing that coincides with the enrichment of several postsynaptic
proteins to pre-plasticity levels. Notably, increasing the level of the
postsynaptic scaffolding protein, PSD95, but not of PSD93, overcomes the
refractory period. Our results support a model in which potentiation at a
single synapse is sufficient to initiate a synapse-specific refractory
period that persists until key postsynaptic proteins regain their
steady-state synaptic levels.