It is now well accepted that transitions between sleep and wakefulness are regulated by complex neurobiologic mechanisms, which, ultimately, can be delineated as oscillations between two opponent processes, one promoting sleep and the other promoting wakefulness.
The role of several neurotransmitter or neuromodulator systems, including noradrenergic, serotonergic, cholinergic, adenosinergic, and histaminergic systems and, more recently, the hypocretin/orexin and dopamine systems, has been clearly established.
Amphetamine-like stimulants are known to increase wakefulness by blocking dopamine reuptake, by stimulating dopamine release, or by both mechanisms.