PT  - JOURNAL ARTICLE
AU  - Bruno Pradier
AU  - Katherine Lanning
AU  - Katherine T. Taljan
AU  - Colin J. Feuille
AU  - M. Aurel Nagy
AU  - Julie A. Kauer
TI  - Persistent but labile synaptic plasticity at excitatory synapses
AID  - 10.1523/JNEUROSCI.2772-17.2018
DP  - 2018 May 25
TA  - The Journal of Neuroscience
PG  - 2772-17
4099  - http://www.jneurosci.org/content/early/2018/05/25/JNEUROSCI.2772-17.2018.short
4100  - http://www.jneurosci.org/content/early/2018/05/25/JNEUROSCI.2772-17.2018.full
AB  - Short-term synaptic plasticity contributes to many computations in the brain, and allows synapses to keep a finite record of recent activity. Here we have investigated the mechanisms underlying an intriguing form of short-term plasticity termed labile-LTP, at hippocampal and prefrontal cortex synapses in male rats and male and female mice. In the hippocampus, labile-LTP is triggered by high-frequency activation of presynaptic axons and is rapidly discharged with further activation of those axons. However, if the synapses are quiescent, they remain potentiated until further presynaptic activation. To distinguish labile-LTP from NMDAR-dependent forms of potentiation, we blocked NMDARs in all experiments. Labile-LTP was synapse-specific, and was accompanied by a decreased paired-pulse ratio, consistent with an increased release probability. Presynaptic Ca2+ and protein kinase activation during the tetanus appeared to be required for its initiation. Labile-LTP was not reversed by a PKC inhibitor, and did not require either RIM1α or synaptotagmin 7, proteins implicated in other forms of presynaptic short-term plasticity. Similar NMDAR-independent potentiation could be elicited at synapses in medial prefrontal cortex. Labile-LTP allows for rapid information storage that is erased under controlled circumstances, and could have a role in a variety of hippocampal and prefrontal cortical computations related to short-term memory.SIGNIFICANCE STATEMENTChanges in synaptic strength are thought to represent information storage relevant to particular nervous system tasks. A single synapse can exhibit multiple overlapping forms of plasticity that shape information transfer from presynaptic to postsynaptic neuron. Here we investigate the mechanisms underlying labile-LTP, an NMDAR-independent form of plasticity induced at hippocampal synapses. The potentiation is maintained for long periods as long as the synapses are infrequently active, but with regular activation, the synapses are depotentiated. Similar NMDAR-independent potentiation can also be induced at L2/3-to-L5 synapses in medial prefrontal cortex (mPFC). Labile-LTP requires a rise in presynaptic Ca2+ and protein kinase activation, but is unaffected in RIM1α or synaptotagmin-7 mutant mice. Labile-LTP may contribute to short-term or working memory in hippocampus and mPFC.