Environmental modulation of alcohol intake in hamsters: effects of wheel running and constant light exposure.
BACKGROUND
Alcohol abuse leads to marked disruptions of circadian rhythms, and these disturbances in themselves can increase the drive to drink. Circadian clock timing is regulated by light, as well as by nonphotic influences such as food, social interactions, and wheel running. We previously reported that alcohol markedly disrupts photic and nonphotic modes of circadian rhythm regulation in Syrian hamsters. As an extension of this work, we characterize the hedonic interrelationship between wheel running and ethanol (EtOH) intake and the effects of environmental circadian disruption (long-term exposure to constant light [LL]) on the drive to drink.


METHODS
First, we tested the effect of wheel running on chronic free-choice consumption of a 20% (v/v) EtOH solution and water. Second, the effect of this alcohol drinking on wheel running in alcohol-naive animals was investigated. Third, we assessed the influence of LL, known to suppress locomotor activity and cause circadian rhythm disruption, on EtOH consumption and wheel-running behavior.


RESULTS
Inhibitory effects of wheel running on EtOH intake and vice versa were observed. Exposure to LL, while not affecting EtOH intake, induced rhythm splitting in 75% of the animals. Notably, the splitting phenotype was associated with lower levels of EtOH consumption and preference prior to, and throughout, the period of LL exposure.


CONCLUSIONS
These results are evidence that exercise may offer an efficacious clinical approach to reducing EtOH intake. Also, predisposition for light-induced (or other) forms of circadian disruption may modulate the drive to drink.
Hammer
Steven B
SB
Department of Biological Sciences, Kent State University, Kent, Ohio 44242, USA.
Ruby
Christina L
CL
Brager
Allison J
AJ
Prosser
Rebecca A
RA
Glass
John David
JD
D000428:Alcohol Drinking / Q000523:psychology*; D000818:Animals; D002755:Choice Behavior; D021081:Chronobiology Disorders / Q000523:psychology*; D006224:Cricetinae; D008027:Light; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects*; D017440:Photoperiod