Adolescent Rats Are Sensitive To the Positive Rewarding Effects Of Ethanol

MYERS M; PAUTASSI RM; MOLINA J.C.,; SPEAR, LP; SPEAR, N.E.

Washington, DC, USA

Congreso; 40th Annual Meeting International Society for Developmental Psychobiology; 2007

International Society for Developmental Psychobiology

Adolescent rats are less sensitive to the sedative effects of ethanol thanolder animals. Adolescents may also possess greater sensitivity to theappetitive properties of ethanol. However, unlike neonates or infants,ethanol-mediated appetitive behavior has yet to be clearly demonstrated inadolescents. Responsiveness to appetitive ethanol reinforcement wasassessed in adolescent rats through second-order conditioning (SOC). Onpostnatal day 32 (PD32) animals were administered ethanol (0.5 or 2.0 g/kg, ig)paired with intraoral pulses of sucrose (CS1, first-order conditioning phase).CS1 delivery took place either 5–20 (Paired Early) or 30–45 (Paired Late)min after ethanol. Four hours separated CS1 exposure and ethanoladministration in unpaired controls. On PD33, animals were presented theCS1 (second-order conditioning phase) while in a visually and tactiledistinctive chamber (CS2). Then, they were tested for CS2 preference. Bothearly and late Paired pups exhibited greater preference for the CS2 thancontrols, a result indicative of ethanol-mediated reinforcement. During theCS1 - CS2 pairing, paired animals given 2.0 g/kg ethanol wall-climbed morethan controls. Blood ethanol levels associated with the 0.5 and 2.0 g/kgdoses were 33.7, 27.9, 125.7 and 188.4 mg% for the early and late phases,respectively. This data indicate high sensitivity for the appetitive effects ofethanol in adolescent rats when assessed by a second-order conditioningprocedure. Rats also showed EtOH-mediated behavioral activation duringthe second-order conditioning phase. The SOC preparation provides avaluable conditioning model for detecting motivational effects of ethanolduring adolescence. [Supported by grants from the National Institute onAlcohol Abuse and Alcoholism (RO1AA13098 and RO1AA11960) and theNational Institutes of Mental Health (RO1MH35219) to NES]