(-)-1-Phenyl-2-propylaminopentane ((-)-PPAP) is a drug with an unusual effects profile. It can loosely be grouped with the stimulant or antidepressant drug families, but its mechanism of action is quite different.
PPAP is classified as a catecholaminergic and serotonergic activity enhancer. This means that it stimulates the impulse propagation mediated transmitter release of the neurotransmitters dopamine, norepinephrine and serotonin in the brain (although unlike the newer and more potent compound BPAP, it has less impact on serotonin release and affects mainly the catecholamines). Unlike stimulant drugs like amphetamine, which release a flood of monoamine neurotransmitters in an uncontrolled manner, PPAP instead only increases the amount of neurotransmitter that gets released when a neuron is stimulated by receiving an impulse from a neighbouring neuron. So while both amphetamine and PPAP increase the amount of neurotransmitters that get released, amphetamine causes neurons to dump neurotransmitter stores into the synapse regardless of external input, while with PPAP the pattern of neurotransmitter release is not changed, but when the neuron would normally release neurotransmitter, a larger amount than normal is released.
Other drugs which produce this effect are the endogenous trace amines phenethylamine and tyramine, and the neuroprotective MAO-B inhibitor selegiline. However, while selegiline is a potent monoamine oxidase inhibitor, PPAP has no monoamine oxidase inhibitory activity, and produces only the activity enhancer effect.