In summary, under the present experimental circumstances, adolescents, but not adults, acquired ethanol-mediated conditioning. These age-related differences may imply different degrees of vulnerability to ethanol abuse and dependence across age. Adolescence is characterized by behavioral traits such as novelty seeking, impulsivity, increased peer interaction and risk taking (Spear, 2000). It has been proposed that these traits represent “biological markers” for drug abuse or dependence (Kleaubur & Bardo, 1999; Zuckerman, 1994). However, the ontogenetic analysis of ethanol-related learning in phenotypes characterized by varying degrees of overlap between these traits has been scarce. In the rat, this void in the literature is likely to be related to a lack of behavioral techniques sensitive to ethanol’s motivational properties and amenable to being employed with minimal procedural changes across development. The second-order conditioning technique seems to provide a relatively simple and brief screening test to analyze sensitivity for motivational properties of ethanol or of other drugs across ontogeny. Further studies are needed to conclusively determine if the adolescent stage represents a sensitive period in terms of vulnerability to the associative effects of drugs of abuse.
