title: mGluR1/5 subtype-specific calcium signalling and induction of long-term potentiation in rat hippocampal oriens/alveus interneurones.
abstract: Hippocampal inhibitory interneurones demonstrate pathway- and synapse-specific rules of transmission and plasticity, which are key determinants of their role in controlling pyramidal cell excitability. Mechanisms underlying long-term changes at interneurone excitatory synapses, despite their importance, remain largely unknown. We use two-photon calcium imaging and whole-cell recordings to determine the Ca2+ signalling mechanisms linked specifically to group I metabotropic glutamate receptors (mGluR1alpha and mGluR5) and their role in hebbian long-term potentiation (LTP) in oriens/alveus (O/A) interneurones. We demonstrate that mGluR1alpha activation elicits dendritic Ca2+ signals resulting from Ca2+ influx via transient receptor potential (TRP) channels and Ca2+ release from intracellular stores. By contrast, mGluR5 activation produces dendritic Ca2+ transients mediated exclusively by intracellular Ca2+ release. Using Western blot analysis and immunocytochemistry, we show mGluR1alpha-specific extracellular signal-regulated kinase (ERK1/2) activation via Src in CA1 hippocampus and, in particular, in O/A interneurones. Moreover, we find that mGluR1alpha/TRP Ca2+ signals in interneurone dendrites are dependent on activation of the Src/ERK cascade. Finally, this mGluR1alpha-specific Ca2+ signalling controls LTP at interneurone synapses since blocking either TRP channels or Src/ERK and intracellular Ca2+ release prevents LTP induction. Thus, our findings uncover a novel molecular mechanism of interneurone-specific Ca2+ signalling, critical in regulating synaptic excitability in hippocampal networks.
authors.affiliation: Département de Physiologie, Centre de Recherche en Sciences Neurologiques, Université de Montréal, Case Postale 6128, Succursale Centre-Ville, Montréal, Qc, Canada H3C 3J7.
authors.forename: Lisa
authors.initials: L
authors.lastname: Topolnik
authors.forename: Mounia
authors.initials: M
authors.lastname: Azzi
authors.forename: France
authors.initials: F
authors.lastname: Morin
authors.forename: André
authors.initials: A
authors.lastname: Kougioumoutzakis
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lacaille
mesh_terms: D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000201:enzymology*; D017774:Long-Term Potentiation; D008564:Membrane Potentials; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000378:metabolism*; D012118:Resorcinols / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000201:enzymology; D009435:Synaptic Transmission; D050052:TRPC Cation Channels / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D001565:Benzoates; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C578937:Grm5 protein, rat; D011725:Pyridines; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D012118:Resorcinols; D050052:TRPC Cation Channels; C104077:metabotropic glutamate receptor type 1; C079694:alpha-methyl-4-carboxyphenylglycine; C079215:3,5-dihydroxyphenylglycine; C121465:6-methyl-2-(phenylethynyl)pyridine; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium; D005998:Glycine