A new study of the relationship between alcohol intake and wheel-running in hamsters has found that exercise may provide an effective alternative for reducing alcohol intake in humans. The study also found that hamsters that displayed greater sensitivity to the disruptive effects of constant light on circadian rhythms also craved alcohol less.
Results will be published in the September 2010 issue of Alcoholism: Clinical & Experimental Research and are currently available at early view.
"Alcohol abuse, characterized by routine craving for and consumption of alcohol as well as an inability to function normally without it, disrupts both the timing and consolidation of daily circadian rhythms—when to sleep, eat, and mate—driven by the brain circadian clock," explained J. David Glass, professor of biological sciences at Kent State University and corresponding author for the study. "With continual alcohol use, one may go to bed too early or late, not sleep across the night, and have an unusual eating regime, eating little throughout the day and/or overeating at night. This can lead to a vicious cycle of drinking because these individuals, in response, will consume more alcohol to fall asleep easier only to complain of more disrupted sleep across the night and additionally have a greater craving for alcohol."
In other words, said Alan M. Rosenwasser, professor of psychology at the University of Maine, chronic alcohol abuse and circadian disruption become reciprocally destructive and result in negative effects on physical and emotional health. "It is therefore very interesting that access to running wheels or other forms of voluntary exercise in animal experiments has emerged as a powerful environmental factor influencing brain health, circadian rhythms, and emotional well-being," he said.
Glass agreed, noting that exercise is important in the non-photic regulation of circadian timing. "Restricting animals from exercising," he said, "such as blocking access to a running wheel as we did in this study, had a significant stimulatory effect on alcohol consumption."
Glass and his colleagues tested for three things: the effects of wheel-running on chronic free-choice consumption of an alcohol (20% v/v) and water solution; the effects of alcohol consumption on wheel-running in alcohol-naïve hamsters; and the influence of constant light (LL) on both alcohol consumption and wheel-running behavior.
"In this study, we found that the more the hamsters ran, the less they consumed alcohol," said Glass. "The ‘lazier’ hamsters that did not run as much had a greater craving for and consumption of alcohol, suggesting that exercise may be an effective, beneficial, and non-pharmacologic treatment option for alcoholism."
A second key finding was that hamsters that displayed greater sensitivity to the disruptive effects of constant light on circadian rhythms also craved alcohol less. "Thus, there may be an underlying genetic predisposition for alcohol dependence and abuse that is expressed under challenging circadian conditions," said Glass, "such as shift work, sleep problems, or repeated jet-lag exposure."
