Acute effects of cocaine in two models of inhibitory control: Implications of non-linear dose effects

Aims: This study examined dose-response effects of oral cocaine on the inhibitory control of behavior in adult cocaine users using two different behavioral models of inhibitory control. Design: Adults (n = 12) with a history of cocaine use performed the stop-signal and cue-dependent go-no-go task to measure inhibitory control of behavior in response to a range of oral cocaine HCl doses (0, 100, 200 and 300 mg). Findings: Although both tasks showed cocaine-induced facilitation of inhibitory control, dose-response functions differed depending on the measures. The stop-signal measure revealed a quadratic dose-response function and the cued go-no-go measure showed a more orderly, linear improvement as a function of dose. Conclusions: The evidence suggests a two-phasic dose-response in which facilitating effects of stimulant drugs on inhibitory control might be limited to a range of intermediate doses, above which improvement is no longer evident and impairing effects could possibly emerge.