Tiflucarbine is a thieno[3,2-e]indole derivative patented by Troponwerke G.m.b.H. und Co. K.-G. as antidepressant. Tiflucarbine acts as a potent inhibitor of the 5-hydroxytryptamine (5-HT) uptake and has no effect on 5-HT2 postsynaptic receptors. In preclinical models, Tiflucarbine down-regulates the noradrenaline responses of the cAMP system in rats cerebral cortex. Tiflucarbine treatment increased the specific activity of soluble calmodulin (CaM)-dependent phosphodiesterase in rat brain. Tiflucarbine bound to CaM and inhibited its interaction with the phosphodiesterase. Adrenergic denervation by 6-hydroxydopamine injection prevented both the beta-adrenoceptor down-regulation and the increase in the specific activity of the phosphodiesterase. Tiflucarbine exerted no effect on the reserpine hypothermia, attenuated the apomorphine hypothermia and enhanced the TRH-induced hyperthermia. It did not prevent tryptamine convulsions or the fenfluramine-induced hyperthermia and inhibited the L-5-hydroxytryptophan-induced head twitches. Tiflucarbine administered repeatedly enhanced the D-amphetamine-induced locomotor hyperactivity and inhibited the clonidine-induced aggressiveness.

Indorenate (TR3369, INDO) is a serotonin-like compound with high affinity for 5- HT1A receptors and a lower affinity for 5-HT1C and 5-HT1B receptors. Indorenate possesses antihypertensive and anxiolytic activity in animal behaviour tests. Similar to other serotonin receptor agonists, Indorenate also has anorectic activity; this effect was blocked by the administration of the 5-HT2A/2C receptor antagonists cinanserin, cyproheptadine, metergoline and methysergide. A unpublished clinical trial confirmed its antihypertensive activity in men.

Acetergamine is a derivative of ergoline, it is an oxytocic agent. Acetergamine is alpha-1 blocker and vasodilator. It has been investigated as a treatment for cerebellar ataxia.

Sunepitron (CP-93,393) is an anxiolytic drug with highly selective serotonin 5-hydroxytryptamine 1A autoreceptor agonist, alpha2-adrenergic antagonist, and dopamine D2 agonist properties. Sunepitron hydrochloride had been in Phase III clinical trials by Pfizer for the treatment of anxiety disorder and depression. However, this research has been discontinued.

Cericlamine (INN) is a potent and moderately selective serotonin reuptake inhibitor (SSRI) of the amphetamine family that was investigated as an antidepressant for the treatment of depression, anxiety disorders, and anorexia nervosa by Jouveinal

Vabicaserin is a 5-hydroxytryptamine 2C (5-HT2C) receptor-selective agonist with an EC50 of 8 nM. Pfizer was developing vabicaserin, an oral serotonin (5-HT)2C receptor agonist, for the treatment of schizophrenia and bipolar disorder. Vabicaserin decreases nucleus accumbens extracellular dopamine levels in rats, without affecting striatal dopamine, indicating mesolimbic selectivity. Vabicaserin had been in phase II clinical trials for the treatment of schizophrenia. However, research of Vabicaserin for the treatment schizophrenia and obesity was discontinued.

Capeserod is benzodioxanoxadiazolone derivative patented by patented by pharmaceutical company Synthelabo S. A. as a novel 5-hydroxytryptamine4 receptor partial agonist with potent cognition-enhancing properties. In cells expressing the 5-HT4(b) and 5-HT4(e) splice variants, Capeserod acted as a partial agonist, stimulating cAMP prodn. with a maximal effect of 40 to 50% of serotonin. However, in the rat esophagus preparation, Capeserod acted as a 5-HT4 antagonist with a pKb of 8.81. In addition, Capeserod potently improved performance in several tests of learning and memory. In the object recognition task, it improved retention at 24 h when administered i.p. or p.o. (0.001-0.1 mg/kg). This effect was antagonized by the 5-HT4 antagonist SDZ 205,557, itself without effect, demonstrating that the promnesic effects of Capeserod are mediated by 5-HT4 agonism. Capeserod also reversed the cognitive deficits of aged rats in the linear maze task and the scopolamine-induced deficit of mice in the water maze task. Furthermore, the combined administration of an inactive dose of Capeserod with the cholinesterase inhibitor rivastigmine resulted in a significant promnesic effect, suggesting a synergistic interaction. Capeserod was devoid of unwanted cardiovascular, gastrointestinal, or central nervous system effects with doses up to more than 100-fold higher than those active in the cognitive tests. These results characterize Capeserod as a novel promnesic agent acting via 5-HT4 receptors, with an excellent preclinical profile.

Lesopitron is a non-benzodiazepine anxiolytic with pre- and post-synaptic 5-HT1A agonist activity. Its structure is similar to that of buspirone. Lesopitron has negligible effects on alpha-adrenergic and dopaminergic receptors [162653], and was more potent than structurally-related 5-HT1A agonists in rat social interaction and marmoset anxiety models. It also countered benzodiazepine withdrawal-induced anxiety in rodents. The acute toxicity of lesopitron is low and it does not potentiate the effects of alcohol or barbiturates. Long-term usage led to reductions in plasma glucose, triglycerides, phospholipids and cholesterol. The most common adverse events associated with lesopitron were somnolence, headache, pharyngitis, and dyspepsia.

Lysergide (LSD) is a semi-synthetic hallucinogen and is one of the most potent drugs known. Recreational use became popular between the 1960s to 1980s, but is now less common. LSD was first synthesized by Albert Hoffman while working for Sandoz Laboratories in Basel in 1938. Some years later, during a re-evaluation of the compound, he accidentally ingested a small amount and described the first ‘trip’. During the 1950s and 1960s, Sandoz evaluated the drug for therapeutic purposes and marketed it under the name Delysid®. It was used for research into the chemical origins of mental illness. Recreational use started in the 1960s and is associated with the ‘psychedelic period’. LSD possesses a complex pharmacological profile that includes direct activation of serotonin, dopamine and norepinephrine receptors. In addition, one of its chief sites of action is that of compound-specific (“allosteric”) alterations in secondary messengers associated with 5HT2A and 5HT2C receptor activation and changes in gene expression. The hallucinogenic effects of LSD are likely due to agonism at 5HT2A and 5HT2C receptors. LSD is also an agonist at the majority of known serotonin receptors, including 5HT1A, 5HT1B, 5HT1D, 5HT5A, 5HT6 and 5HT7 receptors. During the 1960s, LSD was investigated for a variety of psychiatric indications, including the following: as an aid in treatment of schizophrenia; as a means of creating a "model psychosis"; as a direct antidepressant; and as an adjunct to psychotherapy. LSD is listed in Schedule I of the United Nations 1971 Convention on Psychotropic Substances.

Revexepride is a selective 5-hydroxytryptamine receptor 4 agonist and member of a class of prokinetic agents that stimulate gastric emptying. Revexepride is thought to stimulate the release of acetylcholine at the myenteric plexus, leading to increased gastrointestinal contractions. This drug has been evaluated for potential use in treatment of gastroesophageal reflux disease. Phase I studies in healthy volunteers have shown no serious adverse events after administration of revexepride. However, a phase II study reported respiratory, thoracic and mediastinal disorders and pulmonary hypertension in 1 patient (0.85%). Furthermore, a European clinical trial showed that four weeks of treatment did not improve symptoms or gastric emptying in patients with symptoms suggestive of gastroparesis compared to placebo.