SCH-23390 is a potent and selective antagonist of the dopamine-1 and dopamine-5 receptors (Ki = 0.2 and 0.3 nM respectively). It was found to prevent death from d-amphetamine overdose in rats and has also been investigated as a potential treatment for Parkinson's Disease and Bipolar Disorder. A single clinical trial was conducted in healthy humans where SCH-23390 induced akathisia (motor restlessness). Preclinical and clinical trials as therapeutic have been discontinued due to side-effects and lack of efficacy. However, it should be noted that a C11 radiolabeled version of the compound has been synthesized and used as a PET imaging probe for the study of Parkinson's Disease and Huntington's Disease.

SCH-23390 is a potent and selective antagonist of the D1A and D1B dopamine receptors having Ki of 0.2 and 0.3 nM respectively. The C11 radiolabeled version has proven to be useful as a PET imaging probe in humans for the investigation of a number of neurological conditions including Schizophrenia, Parkinson's Disease, and Huntington's Disease. It should be noted that the non-radiolabeled compound did receive preclinical interest as a potential therapeutic (annotated separately), although such efforts have been discontinued due to side-effects and a lack of therapeutic efficacy.

β-phenylethylamine (2-phenylethylamine) is a small amine containing alkaloid synonymous with phenethylamine and the acronym PEA; in the human body it has a neuromodulator/neurotransmitter role and is known as a trace amine due to its low quantity relative to other bioactive amino acids. PEA was characterized as a substrate for type B monoamine oxidase. PEA functions by activating trace amine receptors (including TAAR1 and TAAR2) thereby regulating monoamine turnover. Ring-substituted phenethylamines, commonly known as 2Cs, are designer drugs that are emerging as new drugs of abuse. PEA administration may be therapeutic in selected depressed patients.

3, 4-dihydroxyphenylacetic acid (DOPAC) is a neuronal metabolite of dopamine (DA). DA undergoes monoamine oxidase-catalyzed oxidative deamination to 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is metabolized primarily to 3,4-dihydroxyphenylacetic acid (DOPAC) via aldehyde dehydrogenase, ALDH2. DOPAC exhibits the antiproliferative effect in colon cancer cells. In addition, DOPAC enhances not only the total ALDH activity but also the gene expression of ALDH1A1, ALDH2, and ALDH3A1 in a concentration-dependent manner. The pretreatment of DOPAC completely protects the cells from the acetaldehyde-induced cytotoxicity, thus DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.

Phenylalanine is a biologically essential amino acid that acts as a precursor to tyrosine and the catecholamines (epinephrine, norepinephrine, dopamine, and tyramine), and is a constituent of many central nervous system neuropeptides. Normal dietary levels of phenylalanine are approximately 1-2 grams daily. Phenylalanine appears in two forms which are identical mirror images of each other: L-phenylalanine, a nutritional supplement, and D-phenylalanine, an effective painkiller and antidepressant due to its ability to inhibit the breakdown of enkephalins, the brain’s natural pain killers.