Browsing by Author "Boehm, Stephen L."
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Item ACTIVATION OF GABAA RECEPTORS AND INHIBITION OF NEUROSTEROID SYNTHESIS HAVE SEPARABLE ESTROUS-DEPENDENT EFFECTS ON BINGE DRINKING IN FEMALE MICE(Office of the Vice Chancellor for Research, 2012-04-13) Melón, Laverne C.; Nolan, Zachary T.; Boehm, Stephen L.Alcohol concentrations relevant to the beginning stages of binge intoxica-tion may selectively activate GABAA receptor subtypes expressing δ-subunit proteins (δ-GABAAR). Indeed, administration of agonists that interact with these δ-GABAAR prior to alcohol access, can abolish binge drinking behavior (Melon and Boehm, 2011). Unfortunately, our ability to manipulate binge drinking in females is dependent upon estrous phase. The present experi-ments were designed to clarify the estrous-dependent effects of activation of δ-GABAAR on binge drinking. Specifically, we were interested in demonstrat-ing whether females display more persistent binge drinking as a function of cycle-dependent changes in the synthesis of endogenous neurosteroids that modulate δ-GABAAR. Using the Drinking-in-the-Dark binge-drinking model, regularly cycling female mice were given 2 hours of daily access to alcohol (20%v/v). Vaginal cytology was assessed after each drinking session to track estrous status. In experiment 1, animals were administered gaboxadol (an agonist with high affinity for δ-GABAAR) prior to their 8th day of access. In experiment 2, these methods were repeated, but mice received vehicle or finasteride (a neurosteroid synthesis inhibitor) 22hr prior to their 8th day of access. Results from experiment 1 demonstrated that diestrus females were insensitive to the significant gaboxadol-induced decrease in binge drinking observed for proestrus, estrus and metestrus females. In experiment 2, ve-hicle and finasteride treated diestrus females exhibited gaboxadol-induced reduction of their binge drinking. Surprisingly, finasteride pretreatment sig-nificantly reduced binge drinking for estrus females. These studies suggest that ovarian-linked changes to extrasynaptic GABAA R and to neurosteroid activity may be important factors in the binge consumption of alcohol for females. Future studies will further explore the role that acute stress during diestrus may play in inhibiting the effects of δ-GABAA R activation on binge drinking.Item Alterations in the rate of binge ethanol consumption: implications for preclinical studies in mice(Wiley Blackwell (Blackwell Publishing), 2014-09) Linsenbardt, David N.; Boehm, Stephen L.; Department of Psychology, IU School of ScienceThe rate at which alcohol (ethanol) is consumed has direct impact on its behavioral and subjective effects. For this reason, alterations in the pattern of ethanol consumption as a function of drinking history might be critical to the development and maintenance of alcoholism. Furthermore, because pharmacological interventions aimed at disrupting the motivation to consume ethanol are dependent on the brain/plasma concentrations present when an individual is most likely to engage in consumption of this substance, characterizing temporal drinking patterns might be useful to determine the timing of such treatments. The primary goal of the present study was to evaluate alterations in the timecourse of daily binge (drinking-in-the-dark; DID) ethanol consumption. We gave 14 daily 2 hour DID ethanol or water access sessions to male C57BL/6J (B6) mice using a state of the art volumetric drinking monitoring device. We then, primarily as a proof-of-principle, used the GABAB allosteric modulator GS39783 (GS) to determine how this compound influenced the timecourse of binge-like ethanol intake. The rate of ethanol consumption increased dramatically over sessions with the majority occurring in the first few minutes of the final session. Additionally, ethanol consumption occurring immediately following access was almost completely abolished in mice pre-treated with GS; an effect which was ethanol-specific only at this early time interval. These data characterize progressive alterations in the rate of ethanol intake using the DID model and suggest that careful consideration of prior ethanol history and timing of drug administration are warranted when interpreting results of pre-clinical drug administration studies.Item Bidirectional enantioselective effects of the GABAB receptor agonist baclofen in two mouse models of excessive ethanol consumption(Elsevier, 2015-02) Kasten, Chelsea R.; Blasingame, Shelby N.; Boehm, Stephen L.; Department of Psychology, School of ScienceThe GABAB receptor agonist baclofen has been studied extensively in preclinical models of alcohol-use disorders, yet results on its efficacy have been uncertain. Racemic baclofen, which is used clinically, can be broken down into separate enantiomers of the drug. Baclofen has been shown to produce enantioselective effects in behavioral assays, including those modeling reflexive and sexual behavior. The current studies sought to characterize the enantioselective effects of baclofen in two separate models of ethanol consumption. The first was a Drinking-in-the-Dark procedure that provides "binge-like" ethanol access to mice by restricting access to a 2-h period, 3 h into the dark cycle. The second was a two-bottle choice procedure that utilized selectively bred High Alcohol Preferring 1 (HAP1) mice to model chronic ethanol access. HAP1 mice are selectively bred to consume pharmacologically relevant amounts of ethanol in a 24-h two-bottle choice paradigm. The results showed that baclofen yields enantioselective effects on ethanol intake in both models, and that these effects are bidirectional. Total ethanol intake was decreased by R(+)-baclofen, while total intake was increased by S(-)-baclofen in the binge-like and chronic drinking models. Whereas overall binge-like saccharin intake was significantly reduced by R(+)-baclofen, chronic intake was not significantly altered. S(-)-baclofen did not significantly alter saccharin intake. Neither enantiomer significantly affected locomotion during binge-like reinforcer consumption. Collectively, these results demonstrate that baclofen produces enantioselective effects on ethanol consumption. More importantly, the modulation of consumption is bidirectional. The opposing enantioselective effects may explain some of the variance seen in published baclofen literature.Item Blockade of Striatal Dopamine D1 Receptors Reduces Quinine-Resistant Alcohol Intake(2019-05) Houck, Christa A.; Grahame, Nicholas J.; Boehm, Stephen L.; Logrip, Marian L.; Hopf, F. WoodwardDrinking despite aversive consequences, or compulsive drinking, is a criterion of alcohol use disorder and can be modeled in rodents by adding bitter quinine into alcohol. Previous studies have shown the development of quinine-resistant ethanol (EtOH) drinking following a drinking history, but used animals that achieved relatively low blood alcohol levels. Selectively bred crossed High Alcohol Preferring (cHAP) mice average over 250 mg/dl during a two-bottle choice procedure. Compulsive drinking is hypothesized to be D1-receptor mediated via the dorsolateral striatum (DLS). We hypothesized that 2 weeks of free-choice EtOH would lead to quinine resistance and intra-DLS infusion of a D1-antagonist, SCH23390, would attenuate quinine-resistant alcohol drinking with no effect on non-conflicted EtOH drinking. Infusion of SCH23390 into the DMS would not affect quinine-resistant drinking. cHAP mice had guide cannulae placed in the DLS or DMS and had either two weeks (2W) of EtOH and water two-bottle choice or were EtOH naïve (0W). Mice were infused with either SCH23390 or saline immediately prior to one 10% EtOH and water test day and SCH23390 did not disturb alcohol drinking. The following day, we adulterated the EtOH with 0.32-g/L quinine (0.89 mM), and mice received the same microinjection. For animals cannulated in the DLS, 2W history group infused with saline drank more quinine-adulterated EtOH than the 0W saline mice. While SCH23390 infused 0W animals looked no different from saline treated mice, it attenuated quinine + EtOH intake in the 2W animals to the level of 0W animals. Interestingly, DMS-cannulated mice demonstrated similar behavior, with SCH23390 reducing EtOH + quinine consumption, while leaving EtOH consumption undisturbed. Quinine resistance following 2 weeks of free-choice EtOH consumption is attenuated by acute administration of a D1-antagonist in the DLS, suggesting that an alcohol history induces compulsivity and that dopamine contributes to this behavior. This is unique to compulsive drinking, as non-conflicted EtOH drinking was unaffected.Item Effect of GABRA2 expression in the central nucleus of the amygdala on anxiety and alcohol's anxiolytic capacity in C57BL/6J mice(2016) Smoker, Michael P.; Boehm, Stephen L.; Lapish, Christopher C.; Czachowski, Cristine Lynn; Grahame, Nicholas J.The GABRA2 gene, which encodes the α2 subunit of GABAA receptors, is one of the genes most frequently associated with alcohol-related behavior in human studies (Demers, Bogdan, & Agrawal, 2014). Polymorphisms in GABRA2 have been found to be associated with alcohol dependence, changes in drinking frequency, and alcohol’s stimulating and euphoric effects (Arias et al., 2014; Dick et al., 2014; Edenberg et al., 2004). However, the GABRA2-alcohol relationship may not be direct, as anxiety and impulsiveness have been found to be mediating factors (Enoch, Schwartz, Albaugh, Virkkunen, & Goldman, 2006; Villafuerte, Strumba, Stoltenberg, Zucker, & Burmeister, 2013). Comorbidity of anxiety and alcohol use disorders is both prevalent and clinically relevant (J. P. Smith & Randall, 2012), and GABAA receptors play a significant role in each. Benzodiazepines, primary pharmacologic treatments for anxiety disorders and alcohol withdrawal, facilitate signaling at GABAA receptors, and their anxiolytic effects appear to depend on the presence of α2 subunits in these receptors (Low et al., 2000). The amygdala is widely implicated in both anxiety disorders as well as addiction (Janak & Tye, 2015), and its central nucleus is an important mediator of responses to both alcohol- and stress-related stimuli (Roberto, Gilpin, & Siggins, 2012), some of which may be related to GABRA2 expression within this region (Jin et al., 2014). The aim of the current study was to explore the role of Gabra2 (mouse ortholog of GABRA2) expression within the central nucleus of the amygdala (CeA) in anxiety-related behavior and alcohol’s anxiolytic effects in mice. C57BL/6J (B6) mice underwent surgery for bilateral infusion of GFP-tagged lentivirus targeting Gabra2 or a scramble control lentivirus into the CeA. Following 12-13 days of recovery, mice were assessed for anxiety-like behavior in the elevated plus maze (EPM) naïve or following IP injection of 0, 0.75, or 1.5 g/kg ethanol. After assessment, brains were extracted and sectioned through the CeA. Finally, GFP was quantified, the CeA was collected via laser microdissection, and α2 protein was quantified via ELISA. In mice expressing GFP in the CeA, α2 protein concentrations were lower for Virus mice relative to Control mice. The EPM was anxiogenic, and alcohol was found to be anxiolytic. In naïve mice, while there was no difference between Control mice and Virus mice on any behavioral measure, there were significant correlations between CeA α2 protein concentration and time spent in closed arms as well as both total and average time spent in open arms. In mice receiving injection of 0, 0.75, or 1.5 g/kg ethanol, there was a main effect of dose on several behavioral measures, but no interaction between viral condition and dose, and only a main effect of viral condition on average time spent in closed arms. There were no significant correlations between CeA α2 protein concentration and behavioral measures within any injected dose. These results are consistent with GABRA2-anxiety associations and effects of Gabra2 manipulation on anxiety-like behavior. Furthermore, they suggest that CeA α2 protein concentration is positively related to basal anxiety, which could affect alcohol use through various routes. However, these results also suggest that CeA α2 protein concentration is not related to alcohol’s anxiolytic capacity, at least when acutely administered in alcohol-naïve animals.Item The effect of prior alcohol consumption on the ataxic response to alcohol in high-alcohol preferring mice(Elsevier, 2014-12) Fritz, Brandon M.; Boehm, Stephen L.; Department of Psychiatry, IU School of MedicineWe have previously shown that ethanol-naïve high-alcohol preferring (HAP) mice, genetically predisposed to consume large quantities of alcohol, exhibited heightened sensitivity and more rapid acute functional tolerance (AFT) to alcohol-induced ataxia compared to low-alcohol preferring mice. The goal of the present study was to evaluate the effect of prior alcohol self-administration on these responses in HAP mice. Naïve male and female adult HAP mice from the second replicate of selection (HAP2) underwent 18 days of 24-h, 2-bottle choice drinking for 10% ethanol vs. water, or water only. After 18 days of fluid access, mice were tested for ataxic sensitivity and rapid AFT following a 1.75 g/kg injection of ethanol on a static dowel apparatus in Experiment 1. In Experiment 2, a separate group of mice was tested for more protracted AFT development using a dual-injection approach where a second, larger (2.0 g/kg) injection of ethanol was given following the initial recovery of performance on the task. HAP2 mice that had prior access to alcohol exhibited a blunted ataxic response to the acute alcohol challenge, but this pre-exposure did not alter rapid within-session AFT capacity in Experiment 1 or more protracted AFT capacity in Experiment 2. These findings suggest that the typically observed increase in alcohol consumption in these mice may be influenced by ataxic functional tolerance development, but is not mediated by a greater capacity for ethanol exposure to positively influence within-session ataxic tolerance.Item Genetic relationship between predisposition for binge alcohol consumption and blunted sensitivity to adverse effects of alcohol in mice(Wiley Blackwell (Blackwell Publishing), 2014-05) Fritz, Brandon M.; Cordero, Kristy A.; Barkley-Levenson, Amanda M.; Metten, Pamela; Crabbe, John C.; Boehm, Stephen L.; Department of Psychology, IU School of ScienceBACKGROUND: Initial sensitivity to ethanol (EtOH) and the capacity to develop acute functional tolerance (AFT) to its adverse effects may influence the amount of alcohol consumed and may also predict future alcohol use patterns. The current study assessed sensitivity and AFT to the ataxic and hypnotic effects of EtOH in the first replicate of mice (HDID-1) selectively bred for high blood EtOH concentrations (BECs) following limited access to EtOH in the Drinking in the Dark (DID) paradigm. METHODS: Naïve male and female HDID-1 and HS/Npt mice from the progenitor stock were evaluated in 3 separate experiments. In Experiments 1 and 2, EtOH-induced ataxia was assessed using the static dowel task. In Experiment 3, EtOH-induced hypnosis was assessed by using modified restraint tubes to measure the loss of righting reflex (LORR). RESULTS: HDID-1 mice exhibited reduced initial sensitivity to both EtOH-induced ataxia (p < 0.001) and hypnosis (p < 0.05) relative to HS/Npt mice. AFT was calculated by subtracting the BEC at loss of function from the BEC at recovery (Experiments 1 and 3) or by subtracting BEC at an initial recovery from the BEC at a second recovery following an additional alcohol dose (Experiment 2). The dowel test yielded no line differences in AFT, but HS/Npt mice developed slightly greater AFT to EtOH-induced LORR than HDID-1 (p < 0.05). CONCLUSIONS: These results suggest that HDID-1 mice exhibit aspects of blunted ataxic and hypnotic sensitivity to EtOH which may influence their high EtOH intake via DID, but do not display widely different development of AFT. These findings differ from previous findings with the high alcohol-preferring (HAP) selected mouse lines, suggesting that genetic predisposition for binge, versus other forms of excessive alcohol consumption, is associated with unique responses to EtOH-induced motor incoordination.Item Guanabenz Reverses a Key Behavioral Change Caused by Latent Toxoplasmosis in Mice by Reducing Neuroinflammation(American Society for Microbiology, 2019-04-30) Martynowicz, Jennifer; Augusto, Leonardo; Wek, Ronald C.; Boehm, Stephen L.; Sullivan, William J., Jr.; Microbiology and Immunology, School of MedicineToxoplasma gondii is an intracellular parasite that has infected one-third of humans. The infection is permanent because the replicative form (tachyzoite) converts into a latent tissue cyst form (bradyzoite) that evades host immunity and is impervious to current drugs. The continued presence of these parasitic cysts hinders treatment and leads to chronic infection that has been linked to behavioral changes in rodents and neurological disease in humans. How these behavioral changes occur, and whether they are due to parasite manipulation or the host response to infection, remains an outstanding question. We previously showed that guanabenz possesses antiparasitic activity; here, we show that guanabenz reproducibly lowers brain cyst burden up to 80% in chronically infected male and female BALB/cJ mice when given intraperitoneally but not when administered by gavage or in food. Regardless of the administration route, guanabenz reverses Toxoplasma-induced hyperactivity in latently infected mice. In contrast, guanabenz increases cyst burden when given to chronically infected C57BL/6J mice yet still reverses Toxoplasma-induced hyperactivity. Examination of the brains from chronically infected BALB/cJ and C57BL/6J mice shows that guanabenz decreases inflammation and perivascular cuffing in each strain. Our study establishes a robust model for cyst reduction in BALB/cJ mice and shows for the first time that it is possible to reverse a key behavioral change associated with latent toxoplasmosis. The rescue from parasite-induced hyperactivity correlates with a decrease in neuroinflammation rather than reduced cyst counts, suggesting that some behavioral changes arise from host responses to infection.IMPORTANCE Toxoplasma gondii is a common parasite of animals, including up to one-third of humans. The single-celled parasite persists within hosts for the duration of their life as tissue cysts, giving rise to chronic infection. Latent toxoplasmosis is correlated with neurological dysfunction in humans and results in dramatic behavioral changes in rodents. When infected, mice and rats adapt behaviors that make them more likely to be devoured by cats, the only host that supports the sexual stage of the parasite. In this study, we establish a new mouse model of tissue cyst depletion using a drug called guanabenz and show that it is possible to reverse a key behavior change back to normal in infected animals. We also show that the mechanism appears to have nothing to do with parasite cyst burden but rather the degree of neuroinflammation produced by chronic infection.Item Identifying the role of pre-and postsynaptic GABAB receptors in behavior.(Elsevier, 2015-10) Kasten, Chelsea R.; Boehm, Stephen L.; Department of Psychology, School of ScienceAlthough many reviews exist characterizing the molecular differences of GABAB receptor isoforms, there is no current review of the in vivo effects of these isoforms. The current review focuses on whether the GABAB1a and GABAB1b isoforms contribute differentially to behaviors in isoform knockout mice. The roles of these receptors have primarily been characterized in cognitive, anxiety, and depressive phenotypes. Currently, the field supports a role of GABAB1a in memory maintenance and protection against an anhedonic phenotype, whereas GABAB1b appears to be involved in memory formation and a susceptibility to developing an anhedonic phenotype. Although GABAB receptors have been strongly implicated in drug abuse phenotypes, no isoform-specific work has been done in this field. Future directions include developing site-specific isoform knockdown to identify the role of different brain regions in behavior, as well as identifying how these isoforms are involved in development of behavioral phenotypes.Item Relative fluid novelty differentially alters the time course of limited-access ethanol and water intake in selectively bred high-alcohol-preferring mice(Wiley Blackwell (Blackwell Publishing), 2015-04) Linsenbardt, David N.; Boehm, Stephen L.; Department of Psychology, School of ScienceBACKGROUND: The influence of previous alcohol (ethanol [EtOH])-drinking experience on increasing the rate and amount of future EtOH consumption might be a genetically regulated phenomenon critical to the development and maintenance of repeated excessive EtOH abuse. We have recently found evidence supporting this view, wherein inbred C57BL/6J (B6) mice develop progressive increases in the rate of binge EtOH consumption over repeated drinking-in-the-dark (DID) EtOH access sessions (i.e., "front loading"). The primary goal of this study was to evaluate identical parameters in high-alcohol-preferring (HAP) mice to determine whether similar temporal alterations in limited-access EtOH drinking develop in a population selected for high EtOH preference/intake under continuous (24-hour) access conditions. METHODS: Using specialized volumetric drinking devices, HAP mice received 14 daily 2-hour DID EtOH or water access sessions. A subset of these mice was then given 1 day access to the opposite assigned fluid on day 15. Home cage locomotor activity was recorded concomitantly on each day of these studies. The possibility of behavioral/metabolic tolerance was evaluated on day 16 using experimenter-administered EtOH. RESULTS: The amount of EtOH consumed within the first 15 minutes of access increased markedly over days. However, in contrast to previous observations in B6 mice, EtOH front loading was also observed on day 15 in mice that only had previous DID experience with water. Furthermore, a decrease in the amount of water consumed within the first 15 minutes of access compared to animals given repeated water access was observed on day 15 in mice with 14 previous days of EtOH access. CONCLUSIONS: These data further illustrate the complexity and importance of the temporal aspects of limited-access EtOH consumption and suggest that previous procedural/fluid experience in HAP mice selectively alters the time course of EtOH and water consumption.