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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 561/1/91    most recent jphysiol.2004.072546v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Huang, C.-C. Articles by Hsu, K.-S. Search for Related Content PubMed PubMed Citation Articles by Huang, C.-C. Articles by Hsu, K.-S.

¹ Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan 701, Taiwan

Reversal of long-term potentiation (LTP) by long trains of low-frequency stimulation is generally referred to as depotentiation. One of the intriguing aspects of depotentiation is that the magnitude of depotentiation is inversely proportional to the time lag of depotentiation stimulation following LTP induction. Although the mechanisms underlying depotentiation have been widely explored, the factors that regulate the susceptibility of LTP to depotentiation stimulation remain largely unclear. We now report that multiple trains of high-frequency stimulation provide immediate synaptic resistance to depotentiation stimulation at the mossy fibre–CA3 synapses. The synaptic resistance to depotentiation stimulation depends on the amount of synaptic stimulation used to induce LTP; it is prevented by protein synthesis inhibitors and is input specific. In contrast, neither the transection of mossy fibre axons near granule cell somata nor the application of RNA synthesis inhibitors influences synaptic resistance to depotentiation stimulation. We also provide evidence that the induction of depotentiation is regulated by GABA_B receptors. Application of a GABA_B receptor antagonist significantly promoted the synaptic resistance to depotentiation stimulation, whereas inhibition of GABA transport delayed the onset of this synaptic resistance. These results suggest that local protein synthesis is required for the development of synaptic resistance to depotentiation stimulation, whereas the activation of GABA_B receptors promotes the susceptibility to depotentiation stimulation. These two factors may crucially regulate the reversal and stability of long-term information storage.

(Received 23 July 2004; accepted after revision 31 August 2004; first published online 2 September 2004)
Corresponding author K.-S. Hsu: Department of Pharmacology, College of Medicine, National Cheng Kung University, No. 1, Ta-Hsiue Road, Tainan 701, Taiwan. Email: richard{at}mail.ncku.edu.tw

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