Strain differences in delay discounting between Lewis and Fischer 344 rats at baseline and following acute and chronic administration of d-amphetamine

► LEW rats made more impulsive choices than F344 rats under baseline conditions. ► Acute d-AMP increased self-controlled choice for LEW but not F344 rats. ► Effects of repeated d-AMP depended on delay series rather than rat strain. ► Different drug effects may have resulted from genetic and environmental variables.