Persistent but Labile Synaptic Plasticity at Excitatory Synapses.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Molecular and Cellular Neuroscience

Background:

• Short-term synaptic plasticity enables synapses to retain recent activity records, crucial for brain computations.
• Multiple overlapping forms of synaptic plasticity influence neural information transfer.

Purpose of the Study:

• To investigate the mechanisms of labile long-term potentiation (LTP), a form of short-term plasticity, in hippocampal and prefrontal cortex (PFC) synapses.
• To differentiate labile LTP from N-methyl-D-aspartate receptor (NMDAR)-dependent potentiation.

Main Methods:

• Experiments were conducted on hippocampal and PFC synapses in rats and mice, with NMDARs blocked.
• Synapse-specific potentiation was assessed, along with paired pulse ratio changes.
• The roles of presynaptic Ca2+ influx, protein kinase activation, RIM1α, and synaptotagmin-7 were examined.

Main Results:

• Labile LTP was induced by high-frequency stimulation and rapidly discharged by subsequent activation, but persisted during quiescence.
• This potentiation was NMDAR-independent, synapse-specific, and associated with increased release probability.
• Initiation required presynaptic Ca2+ and protein kinase activation, but not RIM1α or synaptotagmin-7.

Conclusions:

• Labile LTP represents a distinct NMDAR-independent form of synaptic plasticity in the hippocampus and mPFC.
• It allows for transient information storage, erased by controlled presynaptic activity.
• Labile LTP may play a role in hippocampal and prefrontal cortical functions, including short-term and working memory.