title: Slow synaptic transmission mediated by TRPV1 channels in CA3 interneurons of the hippocampus.
abstract: Metabotropic glutamate receptors (mGluRs) modulate various neuronal functions in the central nervous system. Many studies reported that mGluRs have linkages to neuronal disorders such as schizophrenia and autism related disorders, indicating that mGluRs are involved in critical functions of the neuronal circuits. To study this possibility further, we recorded mGluR-induced synaptic responses in the interneurons of the CA3 stratum radiatum using rat hippocampal organotypic slice cultures. Electrical stimulation in the CA3 pyramidal cell layer evoked a slow inward current in the interneurons at a holding potential of -70mV in the presence of antagonists for AMPA/kainate receptors, NMDA receptors, GABAA receptors and GABAB receptors. The slow inward current was blocked in the absence of extracellular calcium, suggesting that this was a synaptic response. The slow excitatory postsynaptic current (EPSC) reversed near 0mV, reflecting an increase in a non-selective cationic conductance. The slow EPSC is mediated by group I mGluRs, as it was blocked by AP3, a group I mGluR antagonist. Neither a calcium chelator BAPTA nor a phospholipase C (PLC) inhibitor U73122 affected the slow EPSC. La(3+), a general TRP channel blocker or capsazepine, a selective TRPV1 channel antagonist significantly suppressed the slow EPSC. DHPG, a selective group I mGluRs agonist induced an inward current, which was suppressed by capsazepine. These results indicate that in the interneurons of the hippocampal CA3 stratum radiatum group I mGluRs activate TRPV1 channels independently of PLC and intracellular Ca(2+), resulting in the slow EPSC in the interneurons.
authors.affiliation: Department of Psychiatry, Kobe University Graduate School of Medicine, Japan; Division of Neurophysiology, Kobe University Graduate School of Medicine, Japan.
authors.forename: Noriomi
authors.initials: N
authors.lastname: Eguchi
authors.affiliation: Department of Psychiatry, Kobe University Graduate School of Medicine, Japan.
authors.forename: Akitoyo
authors.initials: A
authors.lastname: Hishimoto
authors.affiliation: Department of Psychiatry, Kobe University Graduate School of Medicine, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sora
authors.affiliation: Division of Neurophysiology, Kobe University Graduate School of Medicine, Japan; Faculty of Health Sciences, Kobe University Graduate School of Health Sciences, Japan. Electronic address: mori@gold.kobe-u.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Mori
mesh_terms: D000818:Animals; D056654:CA3 Region, Hippocampal / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D019706:Excitatory Postsynaptic Potentials; D006624:Hippocampus / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D042541:Intracellular Space / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology; D009435:Synaptic Transmission; D050916:TRPV Cation Channels / Q000502:physiology*; D046509:Tissue Culture Techniques; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D018094:Receptors, Metabotropic Glutamate; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C104077:metabotropic glutamate receptor type 1; D010738:Type C Phospholipases; D002118:Calcium
keywords: Hippocampus; Interneurons; Intracellular calcium; PLC; TRPV1; mGluR