This study found that modafinil increases motivation in rats, but not in rats that lack the dopamine D1 receptors.
These data support the hypothesis that modafinil increases motivation. Moreover, given the similarity of effects with GBR12909, the data corroborate evidence that the behavioral effects of modafinil may be due to DAT inhibition. Furthermore, the dopamine D1R may play a downstream role in mediating modafinil-induced increases in motivation. Thus studies reporting cognition-enhancing effects of modafinil may have been influenced by its ability to increase motivation.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2849918/
