Adolescent ethanol experience alters immediate and long-term behavioral responses to ethanol odor in observer and demonstrator rats

Amber M Eade,Steven L Youngentob

doi:10.1186/1744-9081-5-23

Abstract

BackgroundThe social transmission of food preference paradigm centers on the finding that observers obtain dietary information through olfactory cues on the breath of a demonstrator peer that has ingested a novel substance. This phenomenon plays a role in ethanol acceptability. Historically, studies using this technique have focused on observer animals in order to study the social transmission process. With respect to ethanol, studies of acute intoxication have shown that the pharmacologic properties of ethanol and hematogenic olfaction can influence the subsequent ethanol odor-mediated responses of the intoxicated animals. These acute studies, however, demonstrate odor aversion. The present study compared the effect of adolescent ethanol exposure, via the social transmission paradigm, on the behavioral response to ethanol odor in both observer and demonstrator animals in adolescence (postnatal day (P) 37) and the persistence of these effects into adulthood (P90).MethodsBeginning on P29, naïve rats received four ethanol or water exposures: one every 48 hours through either direct intragastric infusion or social interaction with an infused peer. The reflexive sniffing response of observers and demonstrators to ethanol odor was tested at P37 or P90 using whole-body plethysmography.ResultsThe behavioral response of adolescent ethanol observers and demonstrators significantly differed between themselves and from their respective water controls. Ethanol and water observers both displayed a greater response to ethanol odor than their respective demonstrator counterparts. Compared to controls, both modes of ethanol exposure produced similar magnitudes of enhancement. At P90, both forms of exposure displayed similar responses to ethanol odor and similar magnitudes of enhancement. Only demonstrators displayed equivalent enhanced responses in both sexes.ConclusionIn contrast to previous studies showing odor aversion following acute ethanol intoxication, within the context of the social transmission paradigm, adolescent demonstrators like observers showed an enhanced behavioral response to ethanol odor. The differential enhanced odor response between observers and demonstrators, despite similar net enhancements relative to controls, suggests the presence of a stress effect from the infusion technique. This finding contrasts previous suggestions that intragastric infusions create minimal stress: an important consideration when conducting ethanol research. This stress effect appears to ameliorate by adulthood.

Highlights

The social transmission of food preference paradigm centers on the finding that observers obtain dietary information through olfactory cues on the breath of a demonstrator peer that has ingested a novel substance
The test of the above hypothesis was predicated on our previous finding that adolescent observer rats exposed to ethanol odor through social interaction with an intoxicated peer resulted in an enhanced olfactory response relative to observer animals exposed to a water demonstrator [4]
Using the social transmission of food odor preference paradigm originally described by Galef and colleagues [1,3], several studies have demonstrated that both naïve infant and adolescent observer rats will increase their preference for ethanol odor, as well as manifest enhanced ethanol intake, as a consequence of social interaction with an ethanol intoxicated peer [e.g., [5,6,7,8,9]]

Summary

Introduction

The social transmission of food preference paradigm centers on the finding that observers obtain dietary information through olfactory cues on the breath of a demonstrator peer that has ingested a novel substance This phenomenon plays a role in ethanol acceptability. The ability for food preferences in rats to be influenced through social interactions centers on the observation that rodents can obtain new appetitive dietary information, at least in part, by interacting with a peer that has ingested a novel substance It is the olfactory cues perceived on the breath of an animal (i.e. demonstrator) that ingested the "novel food" that have been found to impact the acceptability of the substance by a conspecific (i.e.observer) [1,2,3]. That is, experiencing ethanol odor in adolescence, as an observer, enhances the olfactory behavioral response to ethanol odor and augments the known behavioral alterations due to prior fetal exposure with the drug

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