title: Homosynaptic and heterosynaptic inhibition of synaptic tagging and capture of long-term potentiation by previous synaptic activity.
abstract: Long-term potentiation (LTP) is an enhancement of synaptic strength that may contribute to information storage in the mammalian brain. LTP expression can be regulated by previous synaptic activity, a process known as "metaplasticity." Cell-wide occurrence of metaplasticity may regulate synaptic strength. However, few reports have demonstrated metaplasticity at synapses that are silent during activity at converging synaptic inputs. We describe a novel form of cell-wide metaplasticity in hippocampal area CA1. Low-frequency stimulation (LFS) decreased the stability of long-lasting LTP ["late" LTP (L-LTP)] induced later at the same inputs (homosynaptic inhibition) and at other inputs converging on the same postsynaptic cells (heterosynaptic inhibition). Significantly, heterosynaptic inhibition of L-LTP also occurred across basal and apical dendrites ("heterodendritic" inhibition). Because transient early LTP (E-LTP) was not affected by previous LFS, we examined the effects of LFS on the consolidation of E-LTP to L-LTP. The duration of E-LTP induced at one set of inputs can be extended by capturing L-LTP-associated gene products generated by previous activity at other inputs to the same postsynaptic neurons. LFS applied homosynaptically or heterosynaptically before L-LTP induction did not impair synaptic capture by subsequent E-LTP stimulation, suggesting that LFS does not impair L-LTP-associated transcription. In contrast, LFS applied just before E-LTP (homosynaptically or heterosynaptically) prevented synaptic tagging, and capture of L-LTP expression. Thus, LFS inhibits synaptic tagging to impair expression of subsequent L-LTP. Such anterograde inhibition represents a novel way in which synaptic activity can regulate the expression of future long-lasting synaptic plasticity in a cell-wide manner.
authors.affiliation: Laboratory of Synaptic Plasticity, University of Alberta School of Medicine, Edmonton, Alberta, T6G 2H7, Canada.
authors.forename: Jennie Z
authors.initials: JZ
authors.lastname: Young
authors.forename: Peter V
authors.initials: PV
authors.lastname: Nguyen
mesh_terms: D000818:Animals; D003712:Dendrites / Q000378:metabolism; D004558:Electric Stimulation / Q000379:methods; D019706:Excitatory Postsynaptic Potentials; D005260:Female; D015870:Gene Expression; D006624:Hippocampus / Q000502:physiology*; D066298:In Vitro Techniques; D017774:Long-Term Potentiation / Q000502:physiology*; D036881:Long-Term Synaptic Depression / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D009433:Neural Inhibition / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D013997:Time Factors; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D009419:Nerve Tissue Proteins