title: Innate immune factors modulate ethanol interaction with GABAergic transmission in mouse central amygdala.
abstract: Excessive ethanol drinking in rodent models may involve activation of the innate immune system, especially toll-like receptor 4 (TLR4) signaling pathways. We used intracellular recording of evoked GABAergic inhibitory postsynaptic potentials (eIPSPs) in central amygdala (CeA) neurons to examine the role of TLR4 activation by lipopolysaccharide (LPS) and deletion of its adapter protein CD14 in acute ethanol effects on the GABAergic system. Ethanol (44, 66 or 100mM) and LPS (25 and 50μg/ml) both augmented eIPSPs in CeA of wild type (WT) mice. Ethanol (44mM) decreased paired-pulse facilitation (PPF), suggesting a presynaptic mechanism of action. Acute LPS (25μg/ml) had no effect on PPF and significantly increased the mean miniature IPSC amplitude, indicating a postsynaptic mechanism of action. Acute LPS pre-treatment potentiated ethanol (44mM) effects on eIPSPs in WT mice and restored ethanol's augmenting effects on the eIPSP amplitude in CD14 knockout (CD14 KO) mice. Both the LPS and ethanol (44-66mM) augmentation of eIPSPs was diminished significantly in most CeA neurons of CD14 KO mice; however, ethanol at the highest concentration tested (100mM) still increased eIPSP amplitudes. By contrast, ethanol pre-treatment occluded LPS augmentation of eIPSPs in WT mice and had no significant effect in CD14 KO mice. Furthermore, (+)-naloxone, a TLR4-MD-2 complex inhibitor, blocked LPS effects on eIPSPs in WT mice and delayed the ethanol-induced potentiation of GABAergic transmission. In CeA neurons of CD14 KO mice, (+)-naloxone alone diminished eIPSPs, and subsequent co-application of 100mM ethanol restored the eIPSPs to baseline levels. In summary, our results indicate that TLR4 and CD14 signaling play an important role in the acute ethanol effects on GABAergic transmission in the CeA and support the idea that CD14 and TLR4 may be therapeutic targets for treatment of alcohol abuse.
authors.affiliation: Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA. Electronic address: mbajo@scripps.edu.
authors.forename: Michal
authors.initials: M
authors.lastname: Bajo
authors.affiliation: Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
authors.forename: Samuel G
authors.initials: SG
authors.lastname: Madamba
authors.affiliation: Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
authors.forename: Marisa
authors.initials: M
authors.lastname: Roberto
authors.affiliation: Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Yuri A
authors.initials: YA
authors.lastname: Blednov
authors.affiliation: Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
authors.forename: Vasudeva N
authors.initials: VN
authors.lastname: Sagi
authors.affiliation: Department of Chemistry, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Roberts
authors.affiliation: Chemical Biology Research Branch, National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism, Rockville, MD 20852, USA.
authors.forename: Kenner C
authors.initials: KC
authors.lastname: Rice
authors.affiliation: Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: R Adron
authors.initials: RA
authors.lastname: Harris
authors.affiliation: Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, 10550 N. Torrey Pines, La Jolla, CA 92037, USA. Electronic address: geobob@scripps.edu.
authors.forename: George R
authors.initials: GR
authors.lastname: Siggins
mesh_terms: D000818:Animals; D066274:Central Amygdaloid Nucleus / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D000431:Ethanol / Q000494:pharmacology*; D007113:Immunity, Innate; D007155:Immunologic Factors / Q000378:metabolism; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects; D018950:Lipopolysaccharide Receptors / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology / Q000633:toxicity; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D011963:Receptors, GABA-A / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D007155:Immunologic Factors; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D011963:Receptors, GABA-A; D051197:Toll-Like Receptor 4; D000431:Ethanol
keywords: Alcohol; Drug abuse; Extended amygdala; Inflammation; LPS; Neuroimmune; Toll-like receptor