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.

BMS-442606 is an S-enantiomer of 6-hydroxybuspirone and is a 5-HT1A partial agonist. BMS-442606 has advantage of being cleared more slowly from blood compared to the R-enantiomer, but R form showed higher affinity and selectivity for the 5HT1A receptor compared to the S-isomer. Because both isomers together with racemic form were well tolerated and was not found any advantage of one of the enantiomers of over the racemic form. Finally, racemic form was chosen for further clinical development.

Yohimbine is a plant alkaloid with alpha-2-adrenergic blocking activity. Yohimbine has been used as a mydriatic and in the treatment of impotence. The exact mechanism for its use in impotence has not been fully elucidated. Yohimbine exerts antagonist actions at halpha(2A)-AR, h5-HT(1B), h5-HT(1D), and hD(2) sites, partial agonist actions at h5-HT(1A) sites. Yohimbine-mediated norepinephrine release at the level of the corporeal tissues may also be involved. In addition, beneficial effects may involve other neurotransmitters such as dopamine and serotonin and cholinergic receptors. Yohimbine has a mild anti-diuretic action, probably via stimulation of hypothalmic center and release of posterior pituitary hormone. Reportedly yohimbine exerts no significant influence on cardiac stimulation and other effects mediated by (beta)-adrenergic receptors. Its effect on blood pressure, if any, would be to lower it; however, no adequate studies are at hand to quantitate this effect in terms of Yohimbine dosage. Side effect of Yohimbine include anxiety, tremor, palpitations, diarrhea, and supine hypertension.

Penbutolol is a new beta-adrenergic blocking drug approved for the treatment of hypertension. It is a noncardioselective beta-blocker and has intrinsic sympathomimetic activity. Penbutolol is marketed under the trade names Levatol, Levatolol, Lobeta, Paginol, Hostabloc, Betapressin. Penbutolol acts on the β1 adrenergic receptors in both the heart and the kidney. When β1 receptors are activated by catecholamines, they stimulate a coupled G protein that leads to the conversion of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP). The increase in cAMP leads to activation of protein kinase A (PKA), which alters the movement of calcium ions in heart muscle and increases the heart rate. Penbutolol blocks the catecholamine activation of β1 adrenergic receptors and decreases heart rate, which lowers blood pressure. Levatol (Penbutolol) is indicated in the treatment of mild to moderate arterial hypertension. It may be used alone or in combination with other antihypertensive agents, especially thiazide-type diuretics.

LP-20 (1-[2-(4-Methoxyphenyl)phenyl]piperazine) is a potent serotonin 5-HT7 receptor antagonist with a low binding affinity for the 5-HT1A and adrenergic 1 receptor. In animal models LP-20 was investigated as a potential positron emission tomography (PET) radiotracer, due to high synthetic availability of 11C radiolabeled compound. Although [11C] LP-20 exhibited in vitro binding with 5-HT7, moderate brain uptake and relatively stable metabolism in the brain, in vivo evaluation showed limited specificity of [11C] LP-20 for 5-HT7.

Terguride (INN), also known as trans-dihydrolisuride, is a serotonin receptor antagonist and dopamine receptor agonist of the ergoline family. Terguride is approved for and used in the treatment of hyperprolactinemia. Terguride is an oral, potent antagonist of 5-HT2B and 5-HT2A (serotonin) receptors. Serotonin stimulates the proliferation of pulmonary artery smooth muscle cells and induces fibrosis in the wall of pulmonary arteries. Together, this causes vascular remodeling and narrowing of the pulmonary arteries. These changes result in increased vascular resistance and PAH. Due to the potential anti-proliferative and anti-fibrotic activity of terguride, this potential medicine could offer the hope of achieving reversal of pulmonary artery vascular remodeling and attenuation of disease progression. In May 2008, terguride was granted orphan drug status for the treatment of pulmonary arterial hypertension. In May 2010 Pfizer purchased worldwide rights for the drug.

Terguride (INN), also known as trans-dihydrolisuride, is a serotonin receptor antagonist and dopamine receptor agonist of the ergoline family. Terguride is approved for and used in the treatment of hyperprolactinemia. Terguride is an oral, potent antagonist of 5-HT2B and 5-HT2A (serotonin) receptors. Serotonin stimulates the proliferation of pulmonary artery smooth muscle cells and induces fibrosis in the wall of pulmonary arteries. Together, this causes vascular remodeling and narrowing of the pulmonary arteries. These changes result in increased vascular resistance and PAH. Due to the potential anti-proliferative and anti-fibrotic activity of terguride, this potential medicine could offer the hope of achieving reversal of pulmonary artery vascular remodeling and attenuation of disease progression. In May 2008, terguride was granted orphan drug status for the treatment of pulmonary arterial hypertension. In May 2010 Pfizer purchased worldwide rights for the drug.

Alprenolol is a beta adrenoreceptor blocking agent and 5HT1A antagonist, developed by AstraZeneca and now available as generic drug. It is used for treatment of hypertension, angina pectoris due to coronary atherosclerosis and acute myocardial infarction.