Mouse Strain Differences in Oral Operant Ethanol Reinforcement under Continuous Access Conditions

Abstract

The present experiment examined ethanol self-administration in C57BL/6J (C57) and DBA/2J (DBA) mice using a continuous access operant procedure. Adult male C57 and DBA mice were initially trained to perform a lever press response to obtain access to 10% w/v sucrose solution. Subsequently, the mice were placed in operant chambers on a continuous (23 hr/day) basis with access to food (FR1), 10% v/v ethanol (FR4), and water from a sipper tube. C57 mice displayed greater rates of responding on the ethanol-associated lever compared with DBA mice. Responding on the food lever was the same in both strains, but DBA mice consumed greater amounts of water. C57 mice consistently displayed both prandial and nonprandial episodes (bouts) of ethanol responding. DBA mice did not respond for ethanol in bouts. Following 50 consecutive sessions, ethanol concentration was altered every 5 days. Response patterns were determined using 0, 5, 10, 20, and 30% v/v ethanol concentrations. C57 mice displayed concentration-dependent responding on the ethanol lever showing that ethanol was functioning as an effective reinforcer in this strain. In contrast, responding on the ethanol lever by DBA mice did not change as a function of ethanol concentration. Saccharin (0.2% w/v) was subsequently added to the ethanol mixture, and responding was examined at 0, 5, 10, and 20% ethanol concentrations. Overall, ethanol lever responding was increased in both strains. As before, C57 mice showed higher levels of ethanol responding, compared with DBA mice. C57 mice also showed higher responding for saccharin alone. These results are consistent with findings that suggest orally administered ethanol is a more effective reinforcer in C57 mice than in DBA mice. Furthermore, C57 mice engage in ethanol-reinforced responding over a broader range of conditions than DBA mice.

Intracranial Self-Stimulation to Evaluate Abuse Potential of Drugs

“…Administration of ethanol resulted in ICSS facilitation in each strain and did so across a broader range of doses and pretreatment times in DBA/2J mice compared with C57BL/6J mice (Fish et al, 2010). The ability of ethanol to facilitate ICSS in Abuse Potential Testing ICSS in C57BL/6J mice is consistent with its ability to maintain self-administration in this strain, but the effect in DBA/2J mice is inconsistent with data showing that ethanol does not maintain self-administration in this strain (Risinger et al, 1998). Strain-dependence of the effects of THC on ICSS was examined in Lewis, Fischer 344, and Sprague-Dawley rats using a hybrid frequency-rate procedure.…”

Animal Models of Motivation for Drinking in Rodents with a Focus on Opioid Receptor Neuropharmacology

“…Two-bottle choice drinking as the only measure of ethanol's reinforcing capacity potentially is confounded by palatability and lack of information regarding patterns of consumption (Cicero, 1979;Meisch, 1984), and it has been suggested that the operant self-administration technique provides a more reliable test of reinforcement (Meisch, 1984). Several laboratories have successfully developed operant ethanol self-administration procedures using C57BL/6 mice (Risinger, Brown, Doan, & Oakes, 1998;Elmer, Meisch, & George, 1987;Middaugh, Kelley, Cuison, & Groseclose, 1999). In the above experiments, a two-manipulanda (two holes or two levers), limited-access approach was employed in…”

A Null Mutation of the Serotonin 6 Receptor Alters Acute Responses to Ethanol

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