title: Serotonin Attenuates Feedback Excitation onto O-LM Interneurons.
abstract: The serotonergic system is a subcortical neuromodulatory center that controls cortical information processing in a state-dependent manner. In the hippocampus, serotonin (5-HT) is released by ascending serotonergic fibers from the midbrain raphe nuclei, thereby mediating numerous modulatory functions on various neuronal subtypes. Here, we focus on the neuromodulatory effects of 5-HT on GABAergic inhibitory oriens lacunosum-moleculare (O-LM) cells in the hippocampal area CA1 of the rat. These interneurons are thought to receive primarily local excitatory input and are, via their axonal projections to stratum lacunosum-moleculare, ideally suited to control entorhinal cortex input. We show that 5-HT reduces excitatory glutamatergic transmission onto O-LM interneurons. By means of paired recordings from synaptically connected CA1 pyramidal cells and O-LM interneurons we reveal that this synapse is modulated by 5-HT. Furthermore, we demonstrate that the reduction of glutamatergic transmission by serotonin is likely to be mediated via a decrease of calcium influx into presynaptic terminals of CA1 pyramidal cells. This modulation of excitatory synaptic transmission onto O-LM interneurons by 5-HT might be a mechanism to vary the activation of O-LM interneurons during ongoing network activity and serve as a brain state-dependent switch gating the efficiency of entorhinal cortex input to CA1 pyramidal neurons.
authors.affiliation: Neuroscience Research Center, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Böhm
authors.affiliation: Neuroscience Research Center, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Pangalos
authors.affiliation: Neuroscience Research Center, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany Bernstein Center for Computational Neuroscience Berlin, Humboldt-Universität zu Berlin, 10115 Berlin, Germany Cluster of Excellence "NeuroCure", Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany Einstein Foundation Berlin, 10117 Berlin, Germany Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), c/o Charité - Universitätsmedizin Berlin, Neuroscience Research Center, 10117 Berlin, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schmitz
authors.affiliation: Neuroscience Research Center, Charité - Universitätsmedizin Berlin, 10117 Berlin, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Winterer
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D019256:Cadmium Chloride / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D018728:Entorhinal Cortex / Q000166:cytology / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D025461:Feedback, Physiological / Q000187:drug effects*; D018682:GABA Agents / Q000494:pharmacology; D059330:GABAergic Neurons / Q000187:drug effects*; D018698:Glutamic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D018490:Serotonin Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D018682:GABA Agents; D018490:Serotonin Agents; D012701:Serotonin; D018698:Glutamic Acid; D019256:Cadmium Chloride; D002118:Calcium
keywords: 5-HT; CA1; paired recordings; presynaptic neuromodulation