S-14506 was originally identified and developed in France by Scientists at the Institut de Recherches Servier. S-14506 showed potent binding and antagonistic activity against the 5HT1-A receptor. It was found to work synergistically with D2 receptor antagonists and was therefore studied in animal models for depression, psychosis, and anxiety. A tritium labeled version was also studied as a potential 5HT1-A receptor PET imaging agent.

SB-224289 was originally developed by SmithKline, now known as GlaxoSmithKline. It was identified as an antagonist of the 5-hydroxytryptamine receptor 1B (5-HT1B) and subsequently investigated for potential antidepressant activity, although no human trials have been reported. Interestingly, SB-224289 was also found to exhibit antagonistic activity for the antifungal mechanism of Marine Depsipeptide Papuamide A in Candida albicans; although the specific mechanism of action remains unknown.

Selective, potent, orally bioavailable full 5-HT1A antagonist. S-(+)-enantiomer of (±)-LY426965 is more active in comparison with its opposite enantiomer (R)-(-)-LY 426965. LY426965 completely reversed the effects of nicotine withdrawal on the auditory startle reflex in rats. In microdialysis experiments, LY426965, when administered with fluoxetine, significantly increased extracellular levels of serotonin above those achievable with fluoxetine alone. In electrophysiological studies, the administration of LY426965 both blocked and reversed the effects of fluoxetine on 5-HT neuronal activity. Preclinical results indicate that LY426965 may have clinical use as a pharmacotherapy for smoking cessation and depression and related disorders.

WAY-181187 is a high affinity and selective 5-HT6 agonist. It displays 60-fold selectivity over other 5-HT and monoamine receptors. WAY-181187 stimulates cAMP, ERK1/2 and Fyn kinase signaling pathway through serotonin receptor activation. WAY-181187 produced both antidepressant-like and anxiolytic-like effects in the animal model. It had been in phase I clinical trial for the treatment of anxiety disorders but this research has been discontinued.

The selective serotonin reuptake inhibitor fluoxetine consists of equal amounts of R and S stereoisomers (antidepressant Prozac (racemic fluoxetine). Binding to the transporter confirmed selectivity of R- and S-fluoxetine for the 5-HT transporter versus the dopamine (DA) and norepinephrine (NE) human transporters. In addition, receptor binding studies demonstrated significant affinity of R-fluoxetine, but not S-fluoxetine, for human 5-HT(2A) and 5-HT(2C) receptor subtypes. R-fluoxetine acts as an antagonist at 5-HT(2A) and 5-HT(2C) receptors. The attempt to develop a single-enantiomer formulation of fluoxetine for the treatment of depression was unsuccessful. Eli Lilly has terminated its licensing and development agreement with Marlborough, Mass.-based Sepracor for (R)-fluoxetine, the single-isomer version of Lilly's antidepressant Prozac.R-enantiomer of fluoxetine, at its highest administered dose, led to statistically significant prolongation of cardiac repolarization in phase II studies; the studies were subsequently stopped.

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.

Nomifensine was developed by Hoechst AG as a potent inhibitor of noradrenaline, dopamine, and 5-HT uptake displayed antidepressant activity. It was first marketed in the UK in 1977 for the treatment of depression. Between 1977 and 1982 there were reports of hemolytic anemia in association with the drug, and this suspected adverse reaction was included in the 1981 edition of the data Sheet Compendium. FDA published a notice of its determination that Merital capsules were removed from the market for safety reasons.

Nomifensine was developed by Hoechst AG as a potent inhibitor of noradrenaline, dopamine, and 5-HT uptake displayed antidepressant activity. It was first marketed in the UK in 1977 for the treatment of depression. Between 1977 and 1982 there were reports of hemolytic anemia in association with the drug, and this suspected adverse reaction was included in the 1981 edition of the data Sheet Compendium. FDA published a notice of its determination that Merital capsules were removed from the market for safety reasons.

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.

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.