Acute drug effects on habitual and non-habitual responding in crossed high alcohol preferring mice

RATIONALE: Drug reward plays a central role in acquiring drug-seeking behavior. However, subjects may continue using drugs despite negative consequences because self-administration becomes habitual, and divorced from outcome values. Although a history of drug and alcohol use expedite habit acquisition, and in spite of the fact that self-administration leads to intoxication, the acute effects of drugs on habitual responding are not well understood. OBJECTIVES: We sought to observe how acute ethanol and amphetamine affect the balance between habitual and goal-directed behavior, as measured by a fluid-reinforced operant conditioning task. METHODS: Selectively bred crossed high-alcohol-preferring (cHAP) mice were trained on an operant conditioning task reinforced on a variable interval schedule with 1% banana solution, which was subsequently devalued via LiCl pairing in half the animals. Ethanol (1.0 g/kg), amphetamine (2.0 mg/kg), or saline was administered prior to a post-devaluation test. RESULTS: Overall, mice showed habitual behavior, but when divided into high- or low-responding groups based on training response rates, saline-treated, low-responding animals devalued, while saline-treated high-responding animals did not. Furthermore, amphetamine elicited devaluation even in high-responding animals, while ethanol prevented devaluation even in low-responding animals. CONCLUSIONS: These data show that ethanol shifts animals toward behaving habitually. This may illuminate why alcohol-intoxicated individuals display impaired judgment about the relative merits of drinking, and potentially serve as a mechanism by which intoxicated subjects resume previously devalued behaviors, such as comorbid drug use. These findings also show that high variable interval response rates facilitate a shift from goal-directed to habitual behavior

Selected lines and inbred strains. Tools in the hunt for the genes involved in alcoholism

In their quest to elucidate the genetic influences contributing to alcoholism, researchers have long used selected lines and inbred strains of rodents. Selected lines are obtained by repeatedly mating those animals within a population that show extremely high or low values of the desired trait. Inbred strains are generated by mating male and female siblings, irrespective of any particular trait, over several generations. Both of these approaches have provided researchers with extensive knowledge about the genetic and neurobiological mechanisms contributing to alcohol-related traits. However, the use of these models is associated with some limitations, mostly resulting from the inbreeding involved in generating such lines and strains. Nevertheless, these models can offer some advantages over other genetic approaches, such as the analysis of quantitative trait loci or the generation of transgenic and knockout mice

Pharmacologically relevant intake during chronic, free-choice drinking rhythms in selectively bred high alcohol-preferring mice

Multiple lines of high alcohol-preferring (HAP) mice were selectively bred for their intake of 10% ethanol (v/v) during 24-hour daily access over a 4-week period, with the highest drinking lines exhibiting intakes in excess of 20 g/kg/day. We observed circadian drinking patterns and resulting blood ethanol concentrations (BECs) in the HAP lines. We also compared the drinking rhythms and corresponding BECs of the highest drinking HAP lines to those of the C57BL/6J (B6) inbred strain. Adult male and female crossed HAP (cHAP), HAP replicate lines 1, 2, 3 and B6 mice had free-choice access to 10% ethanol and water for 3 weeks prior to bi-hourly assessments of intake throughout the dark portion of the light-dark cycle. All HAP lines reached and maintained a rate of alcohol intake above the rate at which HAP1 mice metabolize alcohol, and BECs were consistent with this finding. Further, cHAP and HAP1 mice maintained an excessive level of intake throughout the dark portion of the cycle, accumulating mean BEC levels of 261.5 ± 18.09 and 217.9 ± 25.02 mg/dl, respectively. B6 mice drank comparatively modestly, and did not accumulate high BEC levels (53.63 + 8.15 mg/dl). Free-choice drinking demonstrated by the HAP1 and cHAP lines may provide a unique opportunity for modeling the excessive intake that often occurs in alcohol-dependent individuals, and allow for exploration of predisposing factors for excessive consumption, as well as the development of physiological, behavioral and toxicological outcomes following alcohol exposure

Emotional reactivity to incentive downshift as a correlated response to selection of high and low alcohol preferring mice and an influencing factor on ethanol intake

Losing a job or significant other are examples of incentive loss that result in negative emotional reactions. The occurrence of negative life events is associated with increased drinking (Keyes, Hatzenbuehler, & Hasin, 2011). Further, certain genotypes are more likely to drink alcohol in response to stressful negative life events (Blomeyer et al., 2008; Covault et al., 2007). Shared genetic factors may contribute to alcohol drinking and emotional reactivity, but this relationship is not currently well understood. We used an incentive downshift paradigm to address whether emotional reactivity is elevated in mice predisposed to drink alcohol. We also investigated if ethanol drinking is influenced in High Alcohol Preferring mice that had been exposed to an incentive downshift. Incentive downshift procedures have been widely utilized to model emotional reactivity, and involve shifting a high reward group to a low reward and comparing the shifted group to a consistently rewarded control group. Here, we show that replicate lines of selectively bred High Alcohol Preferring mice exhibited larger successive negative contrast effects than their corresponding replicate Low Alcohol Preferring lines, providing strong evidence for a genetic association between alcohol drinking and susceptibility to the emotional effects of negative contrast. These mice can be used to study the shared neurological and genetic underpinnings of emotional reactivity and alcohol preference. Unexpectedly, an incentive downshift suppressed ethanol drinking immediately following an incentive downshift. This could be due to a specific effect of negative contrast on ethanol consumption or a suppressive effect on consummatory behavior in general. These data suggest that either alcohol intake does not provide the anticipated negative reinforcement, or that a single test was insufficient for animals to learn to drink following incentive downshift. However, the emotional intensity following incentive downshift provides initial evidence that this type of emotional reactivity may be a predisposing factor in alcoholism

DIFFERENCES IN IMPULSIVITY BETWEEN HIGH-ALCOHOL PREFERRING AND LOW-ALCOHOL PREFERRING MICE IN A DRL TASK

poster abstractHigh impulsivity, the propensity to prefer small immediate rewards to larger delayed rewards, is more observable in alcoholics as well as drug addicts than in non-addicts. However, it remains unclear whether impulsivity precedes and potentially causes substance use disorders. Of particular interest to us is whether the high drinkers differ from low drinkers in their ability to perceive time. In this study we examine differences in impulsivity, as measured by a differential reinforcement of low rates of responding (DRL) task, in mice selectively bred for differences in alcohol consumption, High Alcohol Preferring (HAP-II) and Low Alcohol Preferring (LAP-II) mice. In this task, subjects must inhibit instrumental behavior until an unsignaled DRL interval has elapsed. We hypothesize that due to their previously demonstrated impulsivity, the HAPII mice will perform poorly and receive fewer rewards than LAPII mice. We expect that our results will indicate that due to premature responding, HAPII mice will receive fewer rewards than LAPII mice during the DRL task, but obtain more rewards during a basic fixed interval task, when early responding is not punished. Therefore, alcohol naive HAPII mice will be more impulsive than LAPII mice, as measured by the DRL task. This finding suggests impulsivity is a heritable endophenotype that precedes exposure to alcoholism or drugs

Selection for High Alcohol Preference Drinking in Mice Results in Heightened Sensitivity and Rapid Development of Acute Functional Tolerance to Alcohol’s Ataxic Effects

Selection for High Alcohol Preference Drinking in Mice Results in Heightened Sensitivity and Rapid Development of Acute Functional Tolerance to Alcohol’s Ataxic Effects Brandon M. Fritz , Nicholas J. Grahame , and Stephen L. Boehm II Indiana Alcohol Research Center and Department of Psychology, Indiana University – Purdue University Indianapolis, Indianapolis, IN 46202 Abstract Propensity to develop acute functional (or within session) tolerance to alcohol (ethanol) may influence the amount of alcohol consumed, with higher drinking associated with greater acute functional tolerance (AFT). The goal of the current study was to assess this potential correlated response between alcohol preference and AFT in second and third replicate lines of mice selectively bred for high (HAP2&3) and low (LAP2&3) alcohol preference drinking. Male and female mice were tested for development of AFT on a static dowel task which requires that animals maintain balance on a wooden dowel in order to prevent falling. On test day, each mouse received one (1.75g/kg; Experiment 1) or two (1.75g/kg and 2.0g/kg; Experiment 2) injections of ethanol; an initial administration before being placed on the dowel and in Experiment 2, an additional administration after the first regain of balance on the dowel. Blood samples were taken immediately after loss of balance (when BECs were rising) and at recovery (during falling BECs) in Experiment 1, and after first and second recovery in Experiment 2. It was found that HAP mice fell from the dowel significantly earlier and at lower BECs than LAP mice following the initial injection of ethanol and were therefore more sensitive to its early effects. Furthermore, Experiment 1 detected significantly greater AFT development (BECfalling - BECrising) in HAP mice as compared to LAP mice which occurred within ~30 min, supporting our hypothesis. However, AFT was not different between lines in Experiment 2, indicating that ~30–60 min following alcohol administration, AFT development was similar in both lines. These data show that high alcohol drinking genetically associates with both high initial sensitivity and very early tolerance to the ataxic effects of ethanol

Innate and Acquired Quinine‐Resistant Alcohol, but not Saccharin, Drinking in Crossed High–Alcohol‐Preferring Mice

Background Alcohol consumption despite aversive consequences is often a key component of an alcoholism diagnosis. Free‐choice alcohol consumption despite bitter quinine adulteration in rodents has been seen following several months of free‐choice drinking, but there has been little study of whether prolonged access to other palatable substances such as saccharin yields quinine resistance. Selectively bred crossed high–alcohol‐preferring (cHAP) mice average blood alcohol levels of over 250 mg/dl during free‐choice access, considerably higher than other models. We hypothesized that higher intakes would yield more rapid development of quinine‐resistant alcohol (QRA) drinking and quinine‐resistant saccharin (QRS) drinking. Methods All experiments used male and female cHAP mice. Experiment 1 compared mice with either 0 or 5 weeks of alcohol drinking history, testing varying (0.032, 0.10, 0.32 g/l) quinine concentrations in ethanol. Experiment 2 examined whether innate QR may exist, comparing animals with a 1 or zero day of drinking history. Experiment 3 examined the effect of varying histories (0, 2, or 5 weeks) of free‐choice 10% alcohol drinking on QR alcohol consumption at high quinine concentrations. Finally, Experiment 4 investigated the development of QRS drinking. Results We found that we could not detect a history effect in commonly used quinine concentrations, indicating that cHAP mice are innately quinine resistant to 0.10 g/l quinine. However, we were able to determine that a 2‐week drinking history was sufficient to induce QRA drinking in cHAP mice at extremely high quinine concentrations (0.74 and 0.32 g/l). However, the history effect was specific to QRA, a saccharin drinking history, did not yield QRS drinking. Conclusions These data suggest that an alcohol drinking history induces maladaptive behaviors, such as drinking in spite of negative consequences, a pattern not seen with saccharin. Furthermore, a strong genetic predisposition to drink may promote an innate aversion resistance compared with commonly used inbred strains

Ethanol consumption in mice: relationships with circadian period and entrainment

A functional connection between the circadian timing system and alcohol consumption is suggested by multiple lines of converging evidence. Ethanol consumption perturbs physiological rhythms in hormone secretion, sleep and body temperature, and conversely, genetic and environmental perturbations of the circadian system can alter alcohol intake. A fundamental property of the circadian pacemaker, the endogenous period of its cycle under free-running conditions, was previously shown to differ between selectively bred High- (HAP) and Low- (LAP) Alcohol Preferring replicate 1 mice. To test whether there is a causal relationship between circadian period and ethanol intake, we induced experimental, rather than genetic, variations in free-running period. Male inbred C57Bl/6J mice and replicate 2 male and female HAP2 and LAP2 mice were entrained to light:dark cycles of 26 h or 22 h or remained in a standard 24 h cycle. Upon discontinuation of the light:dark cycle, experimental animals exhibited longer and shorter free-running periods, respectively. Despite robust effects on circadian period and clear circadian rhythms in drinking, these manipulations failed to alter the daily ethanol intake of the inbred strain or selected lines. Likewise, driving the circadian system at long and short periods produced no change in alcohol intake. In contrast with replicate 1 HAP and LAP lines, there was no difference in free-running period between ethanol naïve HAP2 and LAP2 mice. HAP2 mice, however, were significantly more active than LAP2 mice as measured by general home-cage movement and wheel running, a motivated behavior implicating a selection effect on reward systems. Despite a marked circadian regulation of drinking behavior, the free-running and entrained period of the circadian clock does not determine daily ethanol intake

Pairing Neutral Cues with Alcohol Intoxication: New Findings in Executive and Attention Networks

Rationale: Alcohol-associated stimuli capture attention, yet drinkers differ in the precise stimuli that become paired with intoxication. Objectives: Extending our prior work to examine the influence of alcoholism risk factors, we paired abstract visual stimuli with intravenous alcohol delivered covertly and examined brain responses to these Pavlovian conditioned stimuli in fMRI when subjects were not intoxicated. Methods: Sixty healthy drinkers performed task-irrelevant alcohol conditioning that presented geometric shapes as conditioned stimuli. Shapes were paired with a rapidly rising alcohol limb (CS+) using intravenous alcohol infusion targeting a final peak breath alcohol concentration of 0.045 g/dL or saline (CS−) infusion at matched rates. On day two, subjects performed monetary delay discounting outside the scanner to assess delay tolerance and then underwent event-related fMRI while performing the same task with CS+, CS−, and an irrelevant symbol. Results: CS+ elicited stronger activation than CS− in frontoparietal executive/attention and orbitofrontal reward-associated networks. Risk factors including family history, recent drinking, sex, and age of drinking onset did not relate to the [CS+ > CS−] activation. Delay-tolerant choice and [CS+ > CS−] activation in right inferior parietal cortex were positively related. Conclusions: Networks governing executive attention and reward showed enhanced responses to stimuli experimentally paired with intoxication, with the right parietal cortex implicated in both alcohol cue pairing and intertemporal choice. While different from our previous study results in 14 men, we believe this paradigm in a large sample of male and female drinkers offers novel insights into Pavlovian processes less affected by idiosyncratic drug associations

Effects of nicotine on alcohol drinking in female mice selectively-bred for high or low alcohol preference

Background Studies show that repeated nicotine use associates with high alcohol consumption in humans, and that nicotine exposure sometimes increases alcohol consumption in animal models. However, the relative roles of genetic predisposition to high alcohol consumption, the alcohol drinking patterns, and the timing of nicotine exposure both with respect to alcohol drinking and developmental stage remain unclear. The studies here manipulated all these variables, using mice selectively bred for differences in free-choice alcohol consumption to elucidate the role of genetics and nicotine exposure in alcohol consumption behaviors. Methods In Experiments 1 and 2, we assessed the effects of repeated nicotine (0, 0.5 or 1.5 mg/kg) injections immediately before binge-like (drinking-in-the-dark; Experiment 1) or during free-choice alcohol access (Experiment 2) on these alcohol drinking behaviors (immediately after injections and during re-exposure to alcohol access 14 days later) in adult high- (HAP2) and low-alcohol preferring (LAP2) female mice (co-exposure model). In Experiments 3 and 4, we assessed the effects of repeated nicotine (0, 0.5 or 1.5 mg/kg) injections 14 days prior to binge-like and free-choice alcohol access on these alcohol drinking behaviors in adolescent HAP2 and LAP2 female mice (Experiment 3) or adult HAP2 female mice (Experiment 4). Results In Experiment 1, we found that repeated nicotine (0.5 and 1.5 mg/kg) and alcohol co-exposure significantly increased binge-like drinking behavior in HAP2 but not LAP2 mice during the re-exposure phase after a 14-day abstinence period. In Experiment 2, 1.5 mg/kg nicotine injections significantly reduced free-choice alcohol intake and preference in the 3rd hour post-injection in HAP2 but not LAP2 mice. No significant effects of nicotine treatment on binge-like or free-choice alcohol drinking were observed in Experiments 3 and 4. Conclusions These results show that the temporal parameters of nicotine and alcohol exposure, pattern of alcohol access, and genetic predisposition for alcohol preference influence nicotine's effects on alcohol consumption. These findings in selectively bred mice suggest that humans with a genetic history of alcohol-use disorders may be more vulnerable to develop nicotine and alcohol co-use disorders