Activation of silent synapses with sustained but not decremental long-term potentiation.
Silent synapses display no excitatory post-synaptic currents (EPSCs) at resting potentials, but can conduct at depolarized potentials. In the hippocampal CA1 region of young animals, conversion of silent synapses to functional synapses occurs rapidly after pairing post-synaptic depolarization with 1Hz pre-synaptic stimulation, a protocol that also induces long-term potentiation (LTP). LTP appears to have a decremental phase and a sustained phase. Many studies have shown that decremental LTP can be pharmacologically isolated from sustained LTP, suggesting that they represent two distinct forms, rather than "phases" of LTP that are expressed simultaneously through different mechanisms. We investigated whether silent synapse activation (SSA) is associated specifically with the expression of sustained or decremental LTP. We found that under control conditions, in which sustained and decremental LTP were induced, SSA was observed. However, under conditions in which only decremental LTP was expressed (in the presence of a protein kinase antagonist), SSA did not occur. We conclude that SSA is associated with the expression of sustained LTP, not decremental LTP, and requires protein kinase activation. These findings support the hypothesis that decremental and sustained LTP are expressed through different mechanisms.
Kasten
Michael R
MR
Department of Neurology, Baylor College of Medicine, 6501 Fannin Street, Houston, TX 77030, USA.
Fan
Yuan
Y
Schulz
Paul E
PE
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D019311:Staurosporine / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D004791:Enzyme Inhibitors; D011500:Protein Synthesis Inhibitors; D000841:Anisomycin; D011494:Protein Kinases; D019311:Staurosporine