Browsing by Author "Homanics, Gregg E."

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    Genetic and Pharmacologic Manipulation of TLR4 Has Minimal Impact on Ethanol Consumption in Rodents
    (Society for Neuroscience, 2017-02-01) Harris, R. Adron; Bajo, Michal; Bell, Richard L.; Blednov, Yuri A.; Varodayan, Florence P.; Truitt, Jay M.; de Guglielmo, Giordano; Lasek, Amy W.; Logrip, Marian L.; Vendruscolo, Leandro F.; Roberts, Amanda J.; Roberts, Edward; George, Olivier; Mayfield, Jody; Billiar, Timothy R.; Hackam, David J.; Mayfield, R. Dayne; Koob, George F.; Roberto, Marisa; Homanics, Gregg E.; Psychiatry, School of Medicine
    Toll-like receptor 4 (TLR4) is a critical component of innate immune signaling and has been implicated in alcohol responses in preclinical and clinical models. Members of the Integrative Neuroscience Initiative on Alcoholism (INIA-Neuroimmune) consortium tested the hypothesis that TLR4 mediates excessive ethanol drinking using the following models: (1) Tlr4 knock-out (KO) rats, (2) selective knockdown of Tlr4 mRNA in mouse nucleus accumbens (NAc), and (3) injection of the TLR4 antagonist (+)-naloxone in mice. Lipopolysaccharide (LPS) decreased food/water intake and body weight in ethanol-naive and ethanol-trained wild-type (WT), but not Tlr4 KO rats. There were no consistent genotypic differences in two-bottle choice chronic ethanol intake or operant self-administration in rats before or after dependence. In mice, (+)-naloxone did not decrease drinking-in-the-dark and only modestly inhibited dependence-driven consumption at the highest dose. Tlr4 knockdown in mouse NAc did not decrease drinking in the two-bottle choice continuous or intermittent access tests. However, the latency to ethanol-induced loss of righting reflex increased and the duration decreased in KO versus WT rats. In rat central amygdala neurons, deletion of Tlr4 altered GABAA receptor function, but not GABA release. Although there were no genotype differences in acute ethanol effects before or after chronic intermittent ethanol exposure, genotype differences were observed after LPS exposure. Using different species and sexes, different methods to inhibit TLR4 signaling, and different ethanol consumption tests, our comprehensive studies indicate that TLR4 may play a role in ethanol-induced sedation and GABAA receptor function, but does not regulate excessive drinking directly and would not be an effective therapeutic target., SIGNIFICANCE STATEMENT Toll-like receptor 4 (TLR4) is a key mediator of innate immune signaling and has been implicated in alcohol responses in animal models and human alcoholics. Members of the Integrative Neuroscience Initiative on Alcoholism (INIA-Neuroimmune) consortium participated in the first comprehensive study across multiple laboratories to test the hypothesis that TLR4 regulates excessive alcohol consumption in different species and different models of chronic, dependence-driven, and binge-like drinking. Although TLR4 was not a critical determinant of excessive drinking, it was important in the acute sedative effects of alcohol. Current research efforts are directed at determining which neuroimmune pathways mediate excessive alcohol drinking and these findings will help to prioritize relevant pathways and potential therapeutic targets.
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    Influence of nonsynaptic α1 glycine receptors on ethanol consumption and place preference
    (Wiley, 2019-03-18) Muñoz, Braulio; Gallegos, Scarlet; Peters, Christian; Murath, Pablo; Lovinger, David M.; Homanics, Gregg E.; Aguayo, Luis G.; Pharmacology and Toxicology, School of Medicine
    Alcohol abuse leads to great medical, social, and economic burdens throughout the world. It is believed that the rewarding actions of alcohol are mediated by alterations in the mesolimbic dopaminergic system leading to increased levels of dopamine in the nucleus accumbens (nAc). Little is known about the role that ligand gated ion channels (LGIC), such as glycine receptors (GlyR), have in regulating levels of ethanol intake and place preference. In this study, we used Knock-in (KI) mice that have ethanol insensitive α1 GlyRs (KK385/386AA) and a combination of electrophysiological and behavioral approaches to examine how expression of ethanol resistant α1 GlyRs in brain neurons might affect binge drinking and conditioned place preference. Data show that tonic α1 GlyR-mediated currents that modulate accumbal excitability were exclusively sensitive to ethanol only in WT mice. Behavioral studies showed that the KI mice have a higher intake of ethanol upon first exposure to drinking and greater conditioned place preference to ethanol, suggesting that α1 GlyRs in the brain have a protective role against abuse. This study suggests that non-synaptic α1 containing GlyRs have a role in motivational and early reinforcing effects of ethanol and opens a novel opportunity for pharmacotherapy development to treat alcohol use disorders.
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    A long non‐coding RNA (Lrap) modulates brain gene expression and levels of alcohol consumption in rats
    (Wiley, 2021-03) Saba, Laura M.; Hoffman, Paula L.; Homanics, Gregg E.; Mahaffey, Spencer; Daulatabad, Swapna Vidhur; Janga, Sarath Chandra; Tabakoff, Boris; BioHealth Informatics, School of Informatics and Computing
    LncRNAs are important regulators of quantitative and qualitative features of the transcriptome. We have used QTL and other statistical analyses to identify a gene coexpression module associated with alcohol consumption. The "hub gene" of this module, Lrap (Long non-coding RNA for alcohol preference), was an unannotated transcript resembling a lncRNA. We used partial correlation analyses to establish that Lrap is a major contributor to the integrity of the coexpression module. Using CRISPR/Cas9 technology, we disrupted an exon of Lrap in Wistar rats. Measures of alcohol consumption in wild type, heterozygous and knockout rats showed that disruption of Lrap produced increases in alcohol consumption/alcohol preference. The disruption of Lrap also produced changes in expression of over 700 other transcripts. Furthermore, it became apparent that Lrap may have a function in alternative splicing of the affected transcripts. The GO category of "Response to Ethanol" emerged as one of the top candidates in an enrichment analysis of the differentially expressed transcripts. We validate the role of Lrap as a mediator of alcohol consumption by rats, and also implicate Lrap as a modifier of the expression and splicing of a large number of brain transcripts. A defined subset of these transcripts significantly impacts alcohol consumption by rats (and possibly humans). Our work shows the pleiotropic nature of non-coding elements of the genome, the power of network analysis in identifying the critical elements influencing phenotypes, and the fact that not all changes produced by genetic editing are critical for the concomitant changes in phenotype.