Release enhancers force the presynaptic terminal to release more neurotransmitter than it would otherwise release. The most clinically important example is the amphetamine class: amphetamine itself, methamphetamine, dextroamphetamine, mixed amphetamine salts (Adderall), lisdexamfetamine (Vyvanse), and methylphenidate (which acts partly by this mechanism alongside reuptake blockade).
Amphetamines work by entering the presynaptic terminal through the dopamine and norepinephrine transporters, then reversing those transporters. Normally these transporters pump dopamine from the synapse back into the presynaptic terminal (reuptake). When amphetamine reverses them, they pump dopamine the opposite direction — from the terminal out into the synapse. The result is massive elevation of synaptic dopamine and norepinephrine, far above what the neuron would release on its own.
Clinically, amphetamines have dual identity. They are first-line medications for attention-deficit/hyperactivity disorder, where they improve focus, task initiation, and working memory by raising prefrontal dopamine toward the peak of the inverted U we discussed in Stage 8. They are also among the most abused stimulants in the world, with methamphetamine in particular driving an opioid-rivaling overdose epidemic.
The same molecule supports both uses. The therapeutic effect in ADHD comes from modest elevation of dopamine in the PFC. The addictive effect comes from massive elevation of dopamine in the nucleus accumbens. The two effects happen along the same drug-dose continuum, with the therapeutic dose well below the dose that produces euphoria in most ADHD patients. This is part of why ADHD treatment with stimulants, when prescribed and monitored properly, does not typically lead to addiction — the doses and delivery mechanisms used clinically do not produce the rapid dopamine surge that drives reward learning.
Delivery method matters enormously. Slow-release oral preparations (Concerta, Vyvanse, extended-release Adderall) produce gradual rises in synaptic dopamine that support cognition without producing the rapid surge that drives abuse. Immediate-release oral forms produce more rapid rises but still much slower than intranasal, smoked, or injected forms. Methamphetamine smoked or injected produces a near-instantaneous dopamine spike that is profoundly reinforcing — the molecular substrate of the addiction epidemic.
Other release enhancers include tyramine (which can cause hypertensive crisis if you combine it with an MAOI, since the MAOI prevents the breakdown of the released norepinephrine), MDMA (ecstasy) which causes massive serotonin release through reversed SERT, and historically ephedrine and pseudoephedrine (used as decongestants and weight-loss agents, with similar release-enhancing mechanisms at lower potency).
Hold the principle. Step 2 of the synaptic cycle is release. Reverse the transporters and you dump neurotransmitter into the synapse. The therapeutic window depends on dose and delivery method, not just the molecule.