Age-dependent effects of ethanol have been observed frequently. Adolescent subjects show less sensitivity than adult animals to the hypnotic and sedative effects of ethanol but are sometimes more affected than adult conspecifics by the cognitive-impairing effects of the drug (Spear & Varlinskaya, 2005). In terms of ethanol’s motivational effects, Philpot et al. (2003) reported ethanol-induced place preference in 45-day old but not in 35-day old rats given 0.5 or 1.0 g/kg. In fact, the latter dose induced tactile aversion in the P35 adolescent animals. Ethanol (0.2 – 2.0 g/kg) failed to affect preference scores in older animals (P60). Philpot et al. (2003) reported conditioned aversion at P35, whereas, at similar age and dose, conditioned preference was found in the present study. This difference might be explained by procedural differences. Whereas Philpot et al. (2003) employed traditional first order conditioned procedures, the present study used a second-order conditioning paradigm. This brief and relatively simple preparation seems to be highly sensitive for detecting appetitive motivational effects of ethanol in developing rats (Molina et al., 2006, 2007).
