Amygdala stimulation modulates hippocampal synaptic plasticity
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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Communicated by James L. McGaugh, University of California, Irvine, CA, August 19, 2004 (received for review February 5, 2004)
Abstract
Experience-dependent synaptic plasticity is a fundamental feature of neural networks involved in the encoding of information, and the capability of synapses to express plasticity is itself activity-dependent. Here, we introduce a “low-frequency burst stimulation” protocol, which can readily induce both long-term potentiation (LTP) and long-term depression (LTD) at in vivo medial perforant path–dentate gyrus synapses. By varying stimulation parameters, we were able to build a stimulus–response map of synaptic plasticity as a LTP–LTD continuum. The response curve displayed a bidirectional shift toward LTP and LTD, depending on the degree and timing of neural activity of the basolateral amygdala. The range of this plastic modulation was also modified by past activity of the basolateral amygdala, suggesting that the amygdala can arrange its ability to regulate the dentate plastic responses. The effects of the BLA activation were replicated by stimulation of the lateral perforant path and, hence, BLA stimulation may recruit the lateral entorhinal cortex. These results represent a high-order dimension of heterosynaptic modulations of hippocampal synaptic plasticity.
Footnotes
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↵ * To whom correspondence should be addressed. E-mail: ikegaya{at}tk.air.jp.
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Abbreviations: BCM, Bienenstock–Cooper–Monro; BLA, basolateral amygdala; CSD, current source density; DG, dentate gyrus; fEPSP, field excitatory postsynaptic potential; LFBS, low-frequency burst stimulation; LTP, long-term potentiation; LTD, long-term depression; MPP, medial perforant path; LPP, lateral perforant path; TBS, theta-burst stimulation.
- Copyright © 2004, The National Academy of Sciences
