title: Short- and long-term depression at glutamatergic synapses on hippocampal interneurons by group I mGluR activation.
abstract: Group I metabotropic glutamate receptors (mGluRs) are expressed by many interneurons of the hippocampus. Although they have been implicated in short- and long-term synaptic plasticity of glutamatergic transmission, their roles in modulating transmission to interneurons are incompletely understood. The selective group I mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) acutely depressed transmission at synapses in the feed-forward inhibitory pathway made by Schaffer collaterals on interneurons in the rat hippocampal CA1 sub-field. DHPG elicited a qualitatively similar depression at synapses made by pyramidal neuron axon collaterals on interneurons in the feedback circuit in stratum oriens. Selective blockers revealed a link from mGluR1 to reversible, and mGluR5 to long-lasting, depression. The acute DHPG-induced depression was consistently accompanied by an elevation in paired-pulse ratio, implying a presynaptic decrease in release probability. However, it was also attenuated by blocking G-protein and Ca(2+) signalling within the postsynaptic neuron, arguing for a retrograde signalling cascade. The DHPG-evoked depression was unaffected by antagonists of CB1 and GABA(B) receptors but was occluded when presynaptic P/Q-type Ca(2+) channels were blocked. Finally, high-frequency stimulation delivered to an independent conditioning pathway evoked a heterosynaptic reversible depression, which was sensitive to group I mGluR antagonists. Group I mGluRs thus powerfully modulate synaptic excitation of hippocampal interneurons and mediate inter-synaptic cross-talk. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.
authors.affiliation: UCL Institute of Neurology, University College London, Queen Square, London WC1N 3BG, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Le Duigou
authors.forename: Thomas
authors.initials: T
authors.lastname: Holden
authors.forename: Dimitri M
authors.initials: DM
authors.lastname: Kullmann
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives* / Q000494:pharmacology; D009473:Neuronal Plasticity; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists* / Q000502:physiology; D012118:Resorcinols / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects*
chemical_list: D015220:Calcium Channels; D018690:Excitatory Amino Acid Agonists; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; C104077:metabotropic glutamate receptor type 1; D008734:Methoxyhydroxyphenylglycol; C079215:3,5-dihydroxyphenylglycine; D005998:Glycine; C010117:3,4-dihydroxyphenylglycol