Characterization of NMDA induced depression in rat hippocampus: involvement of AMPA and NMDA receptors.
The involvement of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) vs. N-methyl-d-aspartate (NMDA) receptor mediated changes in NMDA-induced long-term depression (LTD) was assessed by monitoring isolated AMPA, isolated NMDA and composite field excitatory postsynaptic potentials (EPSP) in the CA1 area of acute rat hippocampal slices. Application of NMDA (20-50 microM) for 3-5 min led to LTD of both AMPA and NMDA receptor mediated EPSPs with near equal changes of the responses. However, AMPA EPSPs displayed a faster initial recovery than NMDA EPSPs. In addition, during the first 15-25 min after NMDA application, there was a superimposed potentiation of the later, but not early, part of AMPA EPSPs, implying a prolongation of waveform. In contrast, the NMDA EPSP waveform remained unaltered throughout the experiments. While it has been maintained that NMDA-induced depression is equivalent to stimulus-induced LTD, our results reveal additional complexity, suggesting a multitude of changes, most likely at the postsynaptic receptor level.
Li
Rui
R
Department of Medical Biophysics, Göteborg University, Box 433, SE 405 30 Göteborg, Sweden. rui@mednet.gu.se
Dozmorov
Mikhail
M
Hellberg
Fredrik
F
Tian
Ye
Y
Jilderos
Barbro
B
Wigström
Holger
H
D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D036881:Long-Term Synaptic Depression / Q000187:drug effects* / Q000502:physiology; D016202:N-Methylaspartate / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000819:agonists / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000502:physiology*
D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate