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  Neocortical long-term potentiation and long-term depression: Site of expression investigated by infrared-guided laser stimulation

Eder, M., Zieglgänsberger, W., & Dodt, H. (2002). Neocortical long-term potentiation and long-term depression: Site of expression investigated by infrared-guided laser stimulation. Journal of Neuroscience, 22(17), 7558-7568.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-000E-A163-2 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-000E-A164-F
Genre: Journal Article
Alternative Title : J. Neurosci.

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 Creators:
Eder, M1, Author
Zieglgänsberger, W1, Author
Dodt, HU1, Author
Affiliations:
1Max Planck Institute of Psychiatry, Max Planck Society, ou_1607137              

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Free keywords: caged compounds; expression site; LTP; LTD; neocortex; photostimulation
 Abstract: The synaptic site of expression of long-term potentiation (LTP) and long-term depression (LTD) is still a matter of debate. To address the question of presynaptic versus postsynaptic expression of neocortical LTP and LTD in a direct approach, we measured the glutamate sensitivity of apical dendrites of layer 5 pyramidal neurons during LTP and LTD. We used infrared-guided laser stimulation to release glutamate from its "caged" form with high spatial and temporal resolution. Responses to photolytically released glutamate and synaptically evoked EPSPs were recorded with patch-clamp pipettes from the neuronal somata. LTP and LTD could be induced by electrical stimulation at the same synapses in succession. The NMDA receptor-dependent LTD was accompanied by a decrease in the dendritic glutamate sensitivity, suggesting a postsynaptic expression of neocortical LTD. In contrast, LTP was never accompanied by a change in the dendritic glutamate sensitivity. A possible explanation for this finding is a presynaptic expression of neocortical LTP. Another set of experiments corroborated these results: Photolytic application of glutamate with a frequency of 5 Hz caused a long-lasting Ca2+ and NMDA receptor-dependent decrease in the dendritic glutamate sensitivity. In contrast, LTP of dendritic glutamate sensitivity was never induced by photostimulation, despite several experimental modifications to prevent washout of the induction mechanism and to induce a stronger postsynaptic Ca2+ influx. In conclusion, our findings provide strong evidence for a postsynaptic expression of neocortical LTD and favor a primarily presynaptic locus of neocortical LTP

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Language(s): eng - English
 Dates: 2002-09-01
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 4097
ISI: 000177622800028
 Degree: -

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Title: Journal of Neuroscience
  Alternative Title : J. Neurosci.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: -
Pages: - Volume / Issue: 22 (17) Sequence Number: - Start / End Page: 7558 - 7568 Identifier: ISSN: 0270-6474