 For modafinil, this activity has been associated "in vivo" with increased extracellular dopamine levels.In genetically engineered mice lacking the dopamine transporter, modafinil lacked wake-promoting activity, suggesting that this activity was DAT-dependent.However, the wake-promoting effects of modafinil, unlike those of amphetamine, were not antagonized by the dopamine receptor antagonist haloperidol in rats.