Priming of group 2 metabotropic glutamate receptors facilitates induction of long-term depression in the dentate gyrus of freely moving rats.
Activation of group 1 metabotropic glutamate receptors (mGluRs) has been shown to facilitate the induction of tetanically evoked long-term potentiation in vivo, whereas group 2 mGluR antagonists inhibit long-term depression (LTD) in the CA1 region. LTD has not been successfully demonstrated to date in the dentate gyrus of freely moving rats. In this study, it was found that 1-Hz low-frequency stimulation (LFS) when applied via a stimulating electrode chronically implanted in the perforant path, evoked short-term depression (STD) of field excitatory post-synaptic potentials and population spikes measured from the dentate gyrus granule cell layer. Application of the group 2 mGluR agonists (S)-4-carboxyphenylglycine (4C3HPG) or (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) prior to LFS facilitated the expression of LTD. Application of the group 2 mGluR antagonist (2S)-alpha-ethylglutamic acid (EGLU) prior to agonist application prevented the facilitating effect of the agonists on LFS-induced depression. EGLU did not influence the expression of LFS-induced STD. Neither 4C3HPG, DCG-IV nor EGLU had an effect on basal synaptic transmission at the concentrations used. The present study demonstrates that priming of group 2 mGluRs leads to induction of persistent LTD in the dentate gyrus in vivo, consistent with a role for group 2 mGluRs in metaplasticity.
Manahan-Vaughan
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Leibniz Institute for Neurobiology, Department of Neurophysiology, Magdeburg, Germany. manahan@ifn-magdeburg.de
D000818:Animals; D001565:Benzoates / Q000494:pharmacology*; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology; D003521:Cyclopropanes / Q000494:pharmacology*; D018891:Dentate Gyrus / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology*; D005971:Glutamates / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000502:physiology*
D001565:Benzoates; D003521:Cyclopropanes; D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; D018094:Receptors, Metabotropic Glutamate; C108822:metabotropic glutamate receptor 2; C104077:metabotropic glutamate receptor type 1; C017302:alpha-ethylglutamic acid; C082313:2-(2,3-dicarboxycyclopropyl)glycine; C079693:4-carboxyphenylglycine; D005998:Glycine