Alcohol Intake in Prairie Voles is Influenced by the Drinking Level of a Peer

Department of Behavioral Neuroscience, Oregon Health and Science University, Portland, Oregon, USA.
Alcoholism Clinical and Experimental Research (Impact Factor: 3.21). 05/2011; 35(10):1884-90. DOI: 10.1111/j.1530-0277.2011.01533.x
Source: PubMed


Peer interactions can have important effects on alcohol-drinking levels, in some cases increasing use, and in other cases preventing it. In a previous study, we have established the prairie vole as a model animal for the effects of social relationships on alcohol intake and have observed a correlation of alcohol intake between individual voles housed together as pairs. Here, we investigated this correlated drinking behavior, hypothesizing that 1 animal alters its alcohol intake to match the drinking of its partner.
Adult prairie voles were tested for baseline drinking levels with continuous access to 10% alcohol and water for 4 days. In Experiment 1, high alcohol drinkers (>9 g/kg/d) were paired with low alcohol drinkers (<5 g/kg/d) of the same sex on either side of a mesh divider for 4 days with continuous access to the same 2-bottle choice test. In Experiment 2, high drinkers were paired with high drinkers and low drinkers paired with low drinkers. In both experiments, animals were again separated following pairing, and drinking was retested in isolation. In Experiment 3, alcohol-naïve animals were tested for saccharin consumption (0.05%) first in isolation and then in high saccharin drinkers paired with low saccharin drinkers, and then in another isolation period.
In Experiment 1, high drinkers paired with low drinkers significantly decreased their alcohol intake and preference from baseline drinking in isolation, and drinking levels remained significantly lower during isolation following pairing. Interestingly, there was variability between pairs in whether the high drinker decreased or the low drinker increased intake. In Experiment 2, high drinkers paired with high drinkers did not significantly change their intake level or preference, nor did low drinkers paired with low drinkers, and no changes occurred during the subsequent isolation. In Experiment 3, there was no change in saccharin intake or preference when high drinkers were paired with high drinkers or low paired with low, or in the subsequent isolation.
Alcohol drinking of prairie voles can be altered under social conditions, such that 1 animal changes its alcohol intake to more closely match the intake of the other animal, helping to explain previous findings of correlated alcohol drinking. The effect does not extend to saccharin, a naturally rewarding sweet substance. This behavior can be used to model the peer pressure that can often affect alcohol intake in humans.

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    • "It would be problematic to place a male and female in direct physical contact with one another, because this may produce mating responses[23,24]which may further interfere with alcohol drinking behavior; therefore, group-housing studies did not employ both males and females at the same time, limiting the range of social stimulation conditions investigated. Investigators employing proximal cagemate drinking (PCD) procedures have reported that social interaction between males and females induced elevated ethanol drinking in mice[14,15], in rats[6], and in prairie voles[17,25,26]. The earliest study employing PCD procedures[6]evaluated the effects of social housing on ethanol drinking in male rats using a " contact cagemate " procedure where a wire mesh barrier was in place to physically separate the male drinker from the male cagemate. "

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    • "The effects of social interaction during drug access on intake and the development of addiction-like behaviors remain relatively unexplored. Notable exceptions are the recent studies on prairie voles (Microtus ochrogaster) that assessed alcohol drinking in isolated animals and pairs of voles that were housed in mesh-divided cages [23]–[25]. However, these studies still required that the animals be maintained in separate compartments to measure their alcohol intakes. "
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    • "Additionally, the ability of a social partner's presence to block the ADE is independent of the partner's drinking behavior . We have previously observed that when voles have initial access to ethanol in isolation, the presence of a social partner may actually reduce ethanol drinking (Anacker et al., 2011b). This reduction is specific to ethanol, and is not observed when animals consume sucrose, another highly rewarding fluid. "
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