Intermittent availability of ethanol does not always lead to elevated drinking in mice.
OBJECTIVE
Intermittent access (IA) to an alcohol (ethanol) solution can lead rats to higher ethanol intakes than continuous access, and a recent report showed increased drinking in C57BL/6J mice offered 20% ethanol vs. water 3X/week (Prior studies have offered ethanol during 24 h periods, either continuously or intermittently.).


METHODS
We tested the high-preference C57BL/6J inbred mice: we also studied High Drinking in the Dark (HDID) mice, a line we have selectively bred to reach intoxicating blood ethanol levels after a short period of access to a single bottle of 20% ethanol.


RESULTS
Neither HDID or C57BL/6J male mice offered ethanol every other day during only a 4-h access period showed greater daily intake than mice offered ethanol daily for 4 h. There was a small increase in drinking with 24 h IA in C57BL/6J mice. An experiment with HDID mice and their control heterogeneous stock stock modeled closely after a published study with C57BL/6J mice (Hwa, Chu, Levinson SA et al. Persistent escalation of alcohol drinking in C57BL/6J mice with intermittent access to 20% ethanol. Alcohol Clin Exp Res 2011;35:1938-1947) showed no significant elevation with 24 h IA exposure in either sex of any genotype. Finally, a near replication of the Hwa et al. study showed modestly greater intake in C57BL/6J mice, confirming the efficacy of 24 h IA.


CONCLUSIONS
We conclude that 4 h of IA is likely insufficient to elevate drinking in mice. The lack of effect in HDID mice and their controls further suggests that not all genotypes respond to intermittency.
Portland Alcohol Research Center, Department of Behavioral Neuroscience, Oregon Health & Science University, VA Medical Center (R&D 12), 3710 SW US Veterans Hospital Road, Portland, OR 97239, USA. crabbe@ohsu.edu
John C
JC
Crabbe
John H
JH
Harkness
Stephanie E
SE
Spence
Lawrence C
LC
Huang
Pamela
P
Metten
D000428:Alcohol Drinking / Q000235:genetics; D000818:Animals; D001522:Behavior, Animal; D002492:Central Nervous System Depressants / Q000097:blood; D000431:Ethanol / Q000097:blood; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D013997:Time Factors
D002492:Central Nervous System Depressants; D000431:Ethanol