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Selective enhancement of non‐NMDA receptor‐mediated responses following induction of long‐term potentiation in entorhinal cortex
Author(s) -
Yun Sung Hwan,
Huh Kyoon,
Jung Min Whan
Publication year - 2000
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(200001)35:1<1::aid-syn1>3.0.co;2-l
Subject(s) - long term potentiation , nmda receptor , neuroscience , entorhinal cortex , ltp induction , long term depression , hippocampus , term (time) , chemistry , psychology , receptor , ampa receptor , physics , biochemistry , quantum mechanics
The contribution of NMDA receptors to the expression of long‐term potentiation (LTP) is controversial. In entorhinal cortex (EC) previous studies reported either that LTP was exclusively expressed through NMDA receptors or that both NMDA and non‐NMDA receptors were involved in LTP expression. To reexamine this issue, horizontal entorhinal cortical slices were prepared from adult rats and electrical stimulation was delivered in layer II/III, while field potential recordings were made in layer III. In the standard condition (2.5 mM Mg ++ ), LTP was reliably induced by theta burst stimulation, but was blocked by 100 μM D‐AP5, an NMDA receptor antagonist. This corroborates previous reports that NMDA receptor activation is required for induction of EC LTP. The field potential response was not affected by D‐AP5, but completely blocked by 10 μM CNQX, a non‐NMDA receptor antagonist. This indicates that the expression of LTP is mediated by non‐NMDA receptors in the standard condition. LTP of NMDA receptor‐mediated responses was tested by comparing NMDA responses before and after applying theta burst stimulation in medium containing low magnesium (0.4–1 mM). Theta burst stimulation induced 43.2±9.7% increase of non‐NMDA responses (i.e., AP5‐insensitive fast component) but 5.6±9.0% decrease of the NMDA receptor component (AP5‐sensitive slow component). These results indicate that activation of NMDA receptors is critical for induction of LTP, but LTP expression is mediated by non‐NMDA receptors in EC under these experimental conditions. Synapse 34:1–7, 2000. © 2000 Wiley‐Liss, Inc.