title: Synaptic properties of SOM- and CCK-expressing cells in dentate gyrus interneuron networks.
abstract: Hippocampal GABAergic cells are highly heterogeneous, but the functional significance of this diversity is not fully understood. By using paired recordings of synaptically connected interneurons in slice preparations of the rat and mouse dentate gyrus (DG), we show that morphologically identified interneurons form complex neuronal networks. Synaptic inhibitory interactions exist between cholecystokinin (CCK)-expressing hilar commissural associational path (HICAP) cells and among somatostatin (SOM)-containing hilar perforant path-associated (HIPP) interneurons. Moreover, both interneuron types inhibit parvalbumin (PV)-expressing perisomatic inhibitory basket cells (BCs), whereas BCs and HICAPs rarely target HIPP cells. HICAP and HIPP cells produce slow, weak, and unreliable inhibition onto postsynaptic interneurons. The time course of inhibitory signaling is defined by the identity of the presynaptic and postsynaptic cell. It is the slowest for HIPP-HIPP, intermediately slow for HICAP-HICAP, but fast for BC-BC synapses. GABA release at interneuron-interneuron synapses also shows cell type-specific short-term dynamics, ranging from multiple-pulse facilitation at HICAP-HICAP, biphasic modulation at HIPP-HIPP to depression at BC-BC synapses. Although dendritic inhibition at HICAP-BC and HIPP-BC synapses appears weak and slow, channelrhodopsin 2-mediated excitation of SOM terminals demonstrates that they effectively control the activity of target interneurons. They markedly reduce the discharge probability but sharpen the temporal precision of action potential generation. Thus, dendritic inhibition seems to play an important role in determining the activity pattern of GABAergic interneuron populations and thereby the flow of information through the DG circuitry.
authors.affiliation: Physiologisches Institut I, Systemic and Cellular Neuroscience, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany, and.
authors.forename: Shakuntala
authors.initials: S
authors.lastname: Savanthrapadian
authors.affiliation: Physiologisches Institut I, Systemic and Cellular Neuroscience, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany, and.
authors.forename: Thomas
authors.initials: T
authors.lastname: Meyer
authors.affiliation: Physiologisches Institut I, Systemic and Cellular Neuroscience, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany, and.
authors.forename: Claudio
authors.initials: C
authors.lastname: Elgueta
authors.affiliation: Institute for Integrative Neuroanatomy and NeuroCure Cluster, Charité Berlin, 10115 Berlin, Germany.
authors.forename: Sam A
authors.initials: SA
authors.lastname: Booker
authors.affiliation: Institute for Integrative Neuroanatomy and NeuroCure Cluster, Charité Berlin, 10115 Berlin, Germany.
authors.forename: Imre
authors.initials: I
authors.lastname: Vida
authors.affiliation: Physiologisches Institut I, Systemic and Cellular Neuroscience, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany, and marlene.bartos@physiologie.uni-freiburg.de.
authors.forename: Marlene
authors.initials: M
authors.lastname: Bartos
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000075402:Channelrhodopsins; D002766:Cholecystokinin / Q000235:genetics / Q000378:metabolism*; D018891:Dentate Gyrus / Q000166:cytology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000235:genetics; D007395:Interneurons / Q000145:classification / Q000502:physiology*; D008239:Lysine / Q000031:analogs & derivatives / Q000378:metabolism; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D009415:Nerve Net / Q000502:physiology*; D010320:Parvalbumins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013004:Somatostatin / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000502:physiology*
chemical_list: D000075402:Channelrhodopsins; D010320:Parvalbumins; D049452:Green Fluorescent Proteins; D013004:Somatostatin; D002766:Cholecystokinin; C013411:biocytin; D008239:Lysine
keywords: GABA; cholecystokinin; dentate gyrus; interneuron; somatostatin; synaptic transmission