Ethanol-induced locomotor activity in rats: age-related differences and association with ethanol-induced reinforcement

PAUTASSI RM

Sapporo

Congreso; 2012 International Society for Biomedical Research on Alcoholism (ISBRA) World Congress; 2012

Science Council of Japan

Ethanol-induced locomotor activity (LMA) has been proposed as a proxy for ethanol-mediated appetitive reinforcement. In mice, ethanol typically induces stimulatory and depressant motor effects at low (< 2.0 g/kg, Faria et al, 2008) and high doses (>2.0 g/ kg; Quoilin, Didone, Tirelli & Quertemont, 2010), respectively. Mice studies also indicated an inverse relationship between age and sensitivity to ethanol-induced LMA. Quoilin et al. (2010) found significantly greater ethanol-induced LMA in early adolescent mice than in late adolescents or in adult mice, whereas adults exhibited greater sensitivity to ethanol?s sedative effects. Rats, on the other hand, have been considered as being mostly insensitive to ethanol-induced motor stimulation. In a recent study, however, we found reliable ethanol-induced LMA in adolescent rats given high-dose ethanol (i.e., 2.5 g/kg) through the intragastric route and tested in a large open-field arena during the rising limb of the blood ethanol curve (post-administration minutes 5-12). We employed this paradigm to test age-related differences in ethanol-induced LMA. Contrary to our expectations, adolescent and adult rats did not differ in their susceptibility to ethanol-induced LMA. Subsequent experiments analyzed, in adolescent rats, the association between ethanol-induced LMA and ethanol-induced reinforcement. Specifically, ethanol-induced conditioned place preference and conditioned taste aversion (CPP and CTA) were conducted in animals previously screened for ethanol-induced LMA. Based on previous theories (e.g., Wise & Bozarth, 1987; Robison and Berridge, 2008) and studies (Arias, Molina, Spear, 2009), we expected that ethanol-induced LMA would be negatively and positively associated with CTA and CPP scores, respectively. The adolescents exhibited ethanol-induced CPP and CTA, yet these measures of ethanol reinforcement were not associated with ethanol-induced LMA. Overall, the results suggest that rats are sensitive to ethanol-induced LMA, particularly when testing focuses on the early phase of the toxic process, when blood ethanol levels are rising. The results, however, do not support an association between ethanol-induced LMA and conventional measures of ethanol-induced reinforcement.