title: Differential regulation of metabotropic glutamate receptor- and AMPA receptor-mediated dendritic Ca2+ signals by presynaptic and postsynaptic activity in hippocampal interneurons.
abstract: Calcium plays a crucial role as a ubiquitous second messenger and has a key influence in many forms of synaptic plasticity in neurons. The spatiotemporal properties of dendritic Ca2+ signals in hippocampal interneurons are relatively unexplored. Here we use two-photon calcium imaging and whole-cell recordings to study properties of dendritic Ca2+ signals mediated by different glutamate receptors and their regulation by synaptic activity in oriens/alveus (O/A) interneurons of rat hippocampus. We demonstrate that O/A interneurons express Ca2+-permeable AMPA receptors (CP-AMPARs) providing fast Ca2+ signals. O/A cells can also coexpress CP-AMPARs, Ca2+-impermeable AMPARs (CI-AMPARs), and group I/II metabotropic glutamate receptors (mGluRs) (including mGluR1a), in the same cell. CI-AMPARs are often associated with mGluRs, resulting in longer-lasting Ca2+ signals than CP-AMPAR-mediated responses. Finally, CP-AMPAR- and mGluR-mediated Ca2+ signals demonstrate distinct voltage dependence and are differentially regulated by presynaptic and postsynaptic activity: weak synaptic stimulation produces Ca2+ signals mediated by CP-AMPARs, whereas stronger stimulation, or weak stimulation coupled with postsynaptic depolarization, recruits Ca2+ signals mediated by mGluRs. Our results suggest that differential activation of specific glutamate receptor-mediated Ca2+ signals within spatially restricted dendritic microdomains may serve distinct signaling functions and endow oriens/alveus interneurons with multiple forms of Ca2+-mediated synaptic plasticity. Specific activation of mGluR-mediated Ca2+ signals by coincident presynaptic and postsynaptic activity fulfills the conditions for Hebbian pairing and likely underlies their important role in long-term potentiation induction at O/A interneuron synapses.
authors.affiliation: Département de Physiologie, Centre de Recherche en Sciences Neurologiques, Université de Montréal, Montréal, Quebec, Canada H3C 3J7.
authors.forename: Lisa
authors.initials: L
authors.lastname: Topolnik
authors.forename: Patrice
authors.initials: P
authors.lastname: Congar
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lacaille
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D003712:Dendrites / Q000502:physiology*; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology*; D017774:Long-Term Potentiation / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000502:physiology*; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D013997:Time Factors
chemical_list: D018091:Receptors, AMPA; D018094:Receptors, Metabotropic Glutamate