Monoamine releasing agent

A monoamine releasing agent (MRA), or simply monoamine releaser, is a drug that induces the release of one or more monoamine neurotransmitters from the presynaptic neuron into the synapse, leading to an increase in the extracellular concentrations of the neurotransmitters and hence enhanced signaling by those neurotransmitters. The monoamine neurotransmitters include serotonin, norepinephrine, and dopamine; MRAs can induce the release of one or more of these neurotransmitters.

MRAs work by reversing the direction of the monoamine transporters (MATs), including the serotonin transporter (SERT), norepinephrine transporter (NET), and/or dopamine transporter (DAT), causing them to promote efflux of non-vesicular cytoplasmic monoamine neurotransmitter rather than reuptake of synaptic monoamine neurotransmitter. Many, but not all MRAs, also reverse the direction of the vesicular monoamine transporter 2 (VMAT2), thereby additionally resulting in efflux of vesicular monoamine neurotransmitter into the cytoplasm.

A variety of different classes of drugs induce their effects in the body and/or brain via the release of monoamine neurotransmitters. These include psychostimulants and appetite suppressants acting as dopamine and norepinephrine releasers like amphetamine, methamphetamine, and phentermine; sympathomimetic agents acting as norepinephrine releasers like ephedrine and pseudoephedrine; non-stimulant appetite suppressants acting as serotonin releasers like fenfluramine and chlorphentermine; and entactogens acting as releasers of serotonin and/or other monoamines like MDMA. Trace amines like phenethylamine and tryptamine, as well as the monoamine neurotransmitters themselves, are endogenous MRAs. It is thought that monoamine release by endogenous mediators may play some physiological regulatory role.

MRAs must be distinguished from monoamine reuptake inhibitors (MRIs) and monoaminergic activity enhancers (MAEs), which similarly increase synaptic monoamine neurotransmitter levels and enhance monoaminergic signaling but work via distinct mechanisms.