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

Drinking rhythms in alcohol preferring mice

Multiple lines of High Alcohol Preferring (HAP) mice were selectively bred for their intake of 10% ethanol (v/v) during 24-h daily access over a four-week period, with the highest drinking lines exhibiting intakes in excess of 20 g/kg/day. Drinking rhythms and corresponding blood ethanol concentrations (BEC) of the highest drinking HAP lines to those of the C57BL/6J (B6) inbred strain. Adult male and female crossed HAP (cHAP), HAP1 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 a reverse 12:12 light dark cycle. In another cohort of cHAP mice, the same procedure was used to assess bi-hourly ethanol intake, and blood samples were taken across the day to look at the pattern of accumulation in these mice. Finally, considering the high level of intake by cHAP mice, we were interested in assessing whether metabolic and functional tolerance develop following chronic free-choice access, which were assessed using 2.0 and 1.75 g/kg challenge doses of 20% ethanol, respectively. 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 at 7-8 hours following lights off, respectively. B6 mice drank comparatively modestly, and did not accumulate high BEC levels (53.63 ± 8.15 mg/dl). In the cHAP cohort, mean BECs were 112.47 ± 19.91 at 2 hours after lights off, 189.00 ± 27.40 at 6 hours after lights off, 193.80 ± 29.66 at 10 hours after lights off, and 89.68 ± 22.19 at 2 hours after lights on. Further, following 3 weeks of ethanol access, cHAP mice had a faster rate of ethanol metabolism and fewer hind slips than water-only exposed mice (ps \u3c .05). In conclusion, the excessive free-choice drinking demonstrated by the HAP1 and cHAP lines, as well as the pattern of sustained high BECs in cHAP mice, challenge the notion that rodents will not reliably and voluntarily sustain ethanol intake at pharmacologically relevant levels. These results suggest that the highest drinking HAP lines may provide a unique opportunity for modeling the excessive intake that has been observed in alcohol-dependent individuals. Further, we observed that cHAP mice develop both metabolic and functional tolerance to the ataxic effects of ethanol following 3 weeks of free-choice access. Together, these findings support HAP mice as translational rodent model of alcoholism, and provide rationale for exploration of the predisposing factors for excessive consumption, as well as the development of physiological, behavioral, and toxicological outcomes following alcohol exposure

Investigating reactivity to incentive downshift as a correlated response to selection for high alcohol preference and a determinant of rash action and alcohol consumption

Losing a job or a significant other are examples of incentive shifts that result in negative emotional reactions. The occurrence of negative life events is associated with increased drinking, and alleviation of negative emotions has been cited as a drinking motive for individuals with problematic drinking patterns (Keyes et al., 2011; Adams et al., 2012). Further, there is evidence that certain genotypes drink alcohol in response to stressful negative life events (Blomeyer et al., 2008; Covault et al., 2007). It is possible that shared genetic factors contribute to both alcohol drinking and emotional reactivity, but there is a critical need for this relationship to be understood. The first aim of this proposal will use an incentive downshift paradigm to address whether emotional reactivity is elevated in mice predisposed to drink alcohol. The second aim of this proposal will address if reactivity to an incentive shift can result in rash action using a differential reinforcement of low rates of responding task, and whether this response is also associated with a predisposition for high drinking. The third aim of this proposal will investigate if experimenter administered ethanol reduces contrast effects, and if an incentive shift increases ethanol consumption in a high drinking line. The overall goal of this proposal is to investigate whether reactivity to incentive shift is an important mechanism underlying alcohol drinking in these mice, and the role an incentive shift may play in producing rash action and influencing ethanol consumption

Selectively bred crossed high-alcohol-preferring mice drink to intoxication and develop functional tolerance, but not locomotor sensitization during free-choice ethanol access

BACKGROUND: Crossed high-alcohol-preferring (cHAP) mice were selectively bred from a cross of the HAP1 × HAP2 replicate lines and demonstrate blood ethanol concentrations (BECs) during free-choice drinking reminiscent of those observed in alcohol-dependent humans. In this report, we investigated the relationship between free-choice drinking, intoxication, tolerance, and sensitization in cHAP mice. We hypothesized that initially mice would become ataxic after drinking alcohol, but that increased drinking over days would be accompanied by increasing tolerance to the ataxic effects of ethanol (EtOH). METHODS: Male and female cHAP mice had free-choice access to 10% EtOH and water (E), while Water mice (W) had access to water alone. In experiment 1, the first drinking experience was monitored during the dark portion of the cycle. Once E mice reached an average intake rate of ≥1.5 g/kg/h, they, along with W mice, were tested for footslips on a balance beam, and BECs were assessed. In experiments 2, 3, and 4, after varying durations of free-choice 10% EtOH access (0, 3, 14, or 21 days), mice were challenged with 20% EtOH and tested for number of footslips on a balance beam or locomotor stimulant response. Blood was sampled for BEC determination. RESULTS: We found that cHAP mice rapidly acquire alcohol intakes that lead to ataxia. Over time, cHAP mice developed behavioral tolerance to the ataxic effects of alcohol, paralleled by escalating alcohol consumption. However, locomotor sensitization did not develop following 14 days of free-choice EtOH access. CONCLUSIONS: Overall, we observed increases in free-choice drinking with extended alcohol access paralleled by increases in functional tolerance, but not locomotor sensitization. These data support our hypothesis that escalating free-choice drinking over days in cHAP mice is driven by tolerance to alcohol's behavioral effects. These data are the first to demonstrate that escalating free-choice consumption is accompanied by increasing alcohol tolerance. In addition to buttressing the hypothesized importance of tolerance in drinking, our findings suggest that cHAP mice may be a unique, translational resource for studying tolerance as a contributor to and consequence of chronic, excessive EtOH consumption