Characterization of the Mechanism Underlying the Reversal of Long Term Potentiation by Low Frequency Stimulation at Hippocampal CA1 Synapses ,

doi:10.1074/jbc.M106388200

Characterization of the Mechanism Underlying the Reversal of Long Term Potentiation by Low Frequency Stimulation at Hippocampal CA1 Synapses*,210

From the Department of Pharmacology, College of Medicine, National Cheng-Kung University, Tainan City, Taiwan 701, Republic of China

Abstract

Reversal of long term potentiation (LTP) may function to increase the flexibility and storage capacity of neuronal circuits; however, the underlying mechanisms remain incompletely understood. We show that depotentiation induced by low frequency stimulation (LFS) (2 Hz, 10 min, 1200 pulses) was input-specific and dependent onN-methyl-d-aspartate (NMDA) receptor activation. The ability of LFS to reverse LTP was mimicked by a brief application of NMDA. This NMDA-induced depotentiation was blocked by adenosine A₁ receptor antagonist. However, the reversal of LTP by LFS was unaffected by metabotropic glutamate receptor antagonism. This LFS-induced depotentiation was specifically prevented by protein phosphatase (PP)1 inhibitors, okadaic acid, and calyculin A but not by the PP2A or PP2B inhibitors. Furthermore, by using phosphorylation site-specific antibodies, we found that LFS-induced depotentiation is associated with a persistent dephosphorylation of the GluR1 subunit of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor at serine 831, a protein kinase C and calcium/calmodulin-dependent protein kinase II (CaMKII) substrate, but not at serine 845, a substrate of cAMP-dependent protein kinase. This effect was mimicked by bath-applied adenosine or NMDA and was specifically prevented by okadaic acid. Also, the increased phosphorylation of CaMKII at threonine 286 and the decreased PP activity seen with LTP were overcome by LFS, adenosine, or NMDA application. These results suggest that LFS erases LTP through an NMDA receptor-mediated activation of PP1 to dephosphorylate amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and CaMKII in the CA1 region of the hippocampus.

Footnotes

↵* This work was supported by Research Grant 89-B-FA08-1-4 from the Academic Excellence Program of the Ministry of Education of Taiwan, Republic of China.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵210 The on-line version of this article (available athttp://www.jbc.org) contains a figure.
↵‡ To whom correspondence should be addressed: Dept. of Pharmacology, College of Medicine, National Cheng-Kung University, No. 1, Ta-Hsiue Rd., Tainan City 701, Taiwan, Republic of China. Tel.: 886-6-2353535 (Ext. 5498); Fax: 886-6-2749296; E-mail: richard@mail.ncku.edu.tw.
Published, JBC Papers in Press, October 25, 2001, DOI 10.1074/jbc.M106388200
Abbreviations:

LTP

long term potentiation

LFS

low frequency stimulation

NMDA

N-methyl-d-aspartate

PKA

protein kinase A

PKC

protein kinase C

PP

protein phosphatase

AMPA

?

CaMKII

calcium/calmodulin-dependent protein kinase II

ACSF

artificial cerebral spinal fluid

fEPSPs

field excitatory postsynaptic potentials

DPCPX

8-Cyclopentyl-1,3-dipropylxanthine

d-APV

d-2-amino-5-phosphonovalerate

AIDA

aminoindan-1,5-dicarboxylic acid

mGluR

metabotropic glutamate receptor

MCPG

α-methyl-4-carboxyphenylglycine

MAP

mitogen-activated protein
- Received July 9, 2001.
- Revision received September 28, 2001.
The American Society for Biochemistry and Molecular Biology, Inc.