Persistent Escalation of Alcohol Drinking in C57BL/6J Mice With Intermittent Access to 20% Ethanol

Abstract

Background Intermittent access to drugs of abuse, as opposed to continuous access, is hypothesized to induce a kindling-type transition from moderate to escalated use, leading to dependence. Intermittent 24-hour cycles of ethanol access and deprivation can generate high levels of voluntary ethanol drinking in rats. Methods The current study uses C57BL/6J mice (B6) in an intermittent access to 20% ethanol protocol to escalate ethanol drinking levels. Adult male and female B6 mice were given intermittent access to 20% ethanol on alternating days of the week with water available ad libitum. Ethanol consumption during the initial 2 hours of access was compared to a short term, limited access “binge” drinking procedure, similar to drinking-in-the-dark (DID). B6 mice were also assessed for ethanol dependence with handling-induced convulsion (HIC), a reliable measure of withdrawal severity. Results After 3 weeks, male mice given intermittent access to ethanol achieved high stable levels of ethanol drinking in excess of 20 g/kg/24h, reaching above 100 mg/dl BEC, and showed a significantly higher ethanol preference than mice given continuous access to ethanol. Also, mice given intermittent access drank about twice as much as DID mice in the initial 2-hour access period. B6 mice that underwent the intermittent access protocol for longer periods of time displayed more severe signs of alcohol withdrawal. Additionally, female B6 mice were given intermittent access to ethanol and drank significantly more than males (ca. 30 g/kg/24h). Discussion The intermittent access method in B6 mice is advantageous because it induces escalated, voluntary, and preferential per os ethanol intake, behavior that may mimic a cardinal feature of human alcohol dependence, though the exact nature and site of ethanol acting in the brain and blood as a result of intermittent access has yet to be determined.

Involvement of Activated Brain Stress Responsive Systems in Excessive and “Relapse” Alcohol Drinking in Rodent Models: Implications for Therapeutics

“…Consistent with previous studies in mice [Hall et al, 2001;Racz et al, 2008;Hwa et al, 2011;Yoo et al, 2012] and rats (recently reviewed by Becker and Koob 2016), we confirm sex differences in alcohol drinking, with higher alcohol intake in females. The genotype differences in alcohol intake between hypothalamic POMC deficient and wildtype mice are much greater in females than in males.…”

“…It was not clear, however, whether there is an involvement of β-endorphin in regulation of alcohol drinking, as earlier studies using β-endorphin deficient mice show inconsistent results by different groups [Grisel et al, 1999;Grahame et al, 2000;Racz et al, 2008] (Table 2) deficiency resulting from selective deletion of Pomc enhancers [Lam et al, 2015]. Specifically, we determine the effect of tissue-specific Pomc gene manipulation on: (a) "binge" drinking in a DID model [Rhodes et al, 2005]; (b) acquisition and escalation of excessive alcohol drinking in a chronic intermittent access (IA) model [Wise, 1973;Simms et al, 2008;Hwa et al, 2011], and (c) "relapse" drinking in an alcohol deprivation effect (ADE) model in mice of both sexes [Holter and Spanagel, 1999;Heyser et al, 2003]. The wild-type mice exposed to DID rapidly establish stable alcohol drinking behavior with more intake in females, whereas hypothalamic POMC deficient mice of both sexes have less alcohol intake and less preference.…”

Moderate-dose Regular Lifelong Alcohol Intake Changes the Intestinal Flora, Protects against Aging, and Keeps Spatial Memory in the Senescence-accelerated Mouse Prone 8 (SAMP8) Model

“…The intake of a low dose of EtOH, 1% EtOH, by SAMP8 model, did not increase the drinking volume as observed for addiction. A previous study reported that C57BL/6 mice showed a high alcohol preference, escalating their drinking volume, and adaptation to the high concentration of EtOH (54). However, why the liquid consumption was lesser in the EtOH group than in the water group until about 50 weeks of age in this study remains unknown.…”

Compulsive drug use and its neural substrates

“…In that study, rats that received intermittent access to alcohol (i.e., every other day) showed a gradual increase in alcohol intake over time. This escalation of alcohol intake over time in intermittent/every-other-day models has been confirmed by recent studies that have reintroduced this approach in the field of alcoholism research (Simms et al, 2008;Loi et al, 2010;Hwa et al, 2011;Melendez, 2011;Gilpin et al, 2012). Likewise, classic studies by Wolffgramm (1991), Wolffgramm andHeyne (1991, 1995) demonstrated that rats increase their levels of alcohol intake after lengthy periods (i.e., months) of relatively stable ethanol intake.…”