Involvement of 5-HT2 serotonin receptors in cognitive defects induced by aristolochic acid I in mice.

Aristolochic acids (AAs) are a natural bioactive substance found in Chinese herbs, which are widely used for treating diseases. Many studies have demonstrated that AAs have various pharmacological function, while increasing reports indicated its toxicity. However, the role AAs in cognition remains poorly understood. This study explored the neurotoxic effect of aristolochic acid I (AAI), the most toxic component of the AAs family, on hippocampal synaptic plasticity and spatial cognition in mice. C57BL/6 mice were exposed to 5 mg/kg AAI for 4 weeks. After chronic treatment, AAI considerably increased the level of anxiety and the degree of behavioral despair in mice. Working and reference error rates were higher in the AAI exposed mice than in the control. This was further validated by the molecular docking studies, which AAI might interact with 5-HT2 serotonin receptor (5-HT2AR). Mechanism investigation indicated that AAI triggered inflammation in the hippocampus of mice through increasing the activity of Tnf-α-NF-κB-IL-6 signaling pathway. Conclusively, chronic AAI administration causes inflammation, and it possibly also serves as a potential antagonist of 5-HT2AR to influence the cognition function in C57BL/6 mice.

Neuropharmacological and antidepressant-like effects of ZY-1408: A novel serotonin/norepinephrine reuptake inhibitor and serotonin receptor 2C antagonist.

Depression is a common mental illness and leading cause of disability. Most current antidepressants are associated with significant limitations, and in particular, a delayed onset and low rate of efficacy. Consequently, there remains an ongoing need for antidepressants that are either more effective or better tolerated than existing standards. We previously identified ZY-1408 as a drug with a novel chemical structure and potential anti-depressant-like activity. Specifically, ZY-1408 is a novel serotonin 2C (5-HT2C) receptor antagonist and serotonin/norepinephrine (5-HT/NE) reuptake inhibitor. In this study, we further investigated the antidepressant-like efficacy of ZY-1408 using in vitro and in vivo behavioral tests. ZY-1408 showed 5-HT2C receptor antagonist and 5-HT/NE reuptake inhibitor properties in vitro. Meanwhile, ZY-1408 decreased immobility in vivo in a dose-dependent manner in rats (via the forced-swim test) and mice (via the tail-suspension test). The behavioral test results do not appear to result from stimulation of locomotor activity. In chronically stressed rats, repeated ZY-1408 treatment significantly reversed depressive-like behavior, including reduced sucrose preference, decreased locomotor activity, and prolonged time to begin eating. Furthermore, in vivo microdialysis showed that administration of ZY-1408 significantly increased extracellular concentrations of 5-HT and NE in the hippocampus of freely moving rats. Thus, ZY-1408 is a potent and orally active 5-HT2C receptor antagonist and 5-HT/NE reuptake inhibitor with antidepressant-like activity in rodents.

Design, Synthesis, and Pharmacological Characterization of Heterobivalent Ligands for the Putative 5-HT2A/mGlu2 Receptor Complex.

We report the synthesis of the first series of heterobivalent ligands targeting the putative heteromeric 5-HT2A/mGlu2 receptor complex, based on the 5-HT2A antagonist MDL-100,907 and the mGlu2 ago-PAM JNJ-42491293. The functional properties of monovalent and heterobivalent ligands were characterized in 5-HT2A-, mGlu2/Gqo5-, 5-HT2A/mGlu2-, and 5-HT2A/mGlu2/Gqo5-expressing HEK293 cells using a Ca2+ imaging assay and a [3H]ketanserin binding assay. Pronounced functional crosstalk was observed between the two receptors in 5-HT2A/mGlu2 and 5-HT2A/mGlu2/Gqo5 cells. While the synthesized monovalent ligands retained the 5-HT2A antagonist and mGlu2 ago-PAM functionalities, the seven bivalent ligands inhibited 5-HT-induced responses in 5-HT2A/mGlu2 cells and both 5-HT- and Glu-induced responses in 5-HT2A/mGlu2/Gqo5 cells. However, no definitive correlation between the functional potency and spacer length of the ligands was observed, an observation substantiated by the binding affinities exhibited by the compounds in 5-HT2A, 5-HT2A/mGlu2, and 5-HT2A/mGlu2/Gqo5 cells. In conclusion, while functional crosstalk between 5-HT2A and mGlu2 was demonstrated, it remains unclear how these heterobivalent ligands interact with the putative receptor complex.

Ritanserin blocks CaV1.2 channels in rat artery smooth muscles: electrophysiological, functional, and computational studies.

CaV1.2 channel blockers or 5-HT2 receptor antagonists constitute effective therapy for Raynaud's syndrome. A functional link between the inhibition of 5-HT2 receptors and CaV1.2 channel blockade in arterial smooth muscles has been hypothesized. Therefore, the effects of ritanserin, a nonselective 5-HT2 receptor antagonist, on vascular CaV1.2 channels were investigated through electrophysiological, functional, and computational studies. Ritanserin blocked CaV1.2 channel currents (ICa1.2) in a concentration-dependent manner (Kr = 3.61 µM); ICa1.2 inhibition was antagonized by Bay K 8644 and partially reverted upon washout. Conversely, the ritanserin analog ketanserin (100 µM) inhibited ICa1.2 by ~50%. Ritanserin concentration-dependently shifted the voltage dependence of the steady-state inactivation curve to more negative potentials (Ki = 1.58 µM) without affecting the slope of inactivation and the activation curve, and decreased ICa1.2 progressively during repetitive (1 Hz) step depolarizations (use-dependent block). The addition of ritanserin caused the contraction of single myocytes not yet dialyzed with the conventional method. Furthermore, in depolarized rings, ritanserin, and to a lesser extent, ketanserin, caused a concentration-dependent relaxation, which was antagonized by Bay K 8644. Ritanserin and ketanserin were docked at a region of the CaV1.2 α1C subunit nearby that of Bay K 8644; however, only ritanserin and Bay K 8644 formed a hydrogen bond with key residue Tyr-1489. In conclusion, ritanserin caused in vitro vasodilation, accomplished through the blockade of CaV1.2 channels, which was achieved preferentially in the inactivated and/or resting state of the channel. This novel activity encourages the development of ritanserin derivatives for their potential use in the treatment of Raynaud's syndrome.

Evaluation of anti-depressant effects of phthalazinone-based triple-acting small molecules against 5-HT2A, 5-HT2C, and the serotonin transporter.

Development of highly effective, safe, and fast-acting anti-depressants is urgently required for the treatment of major depressive disorder. It has been suggested that targeting 5-HT2A and 5-HT2C in addition to inhibition of serotonin reuptake may be beneficial in generating anti-depressant agents with better pharmacology and less adverse effects. We have developed phthalazinone-based compounds that potently bind to 5-HT2A, 5-HT2C, and the serotonin transporter. The representative compounds 11j and 11l displayed strong binding affinities against these targets, and showed favorable toxicity profiles as determined by hERG binding and CYP inhibition assays. Furthermore, these compounds presented promising anti-depressant effects comparable to fluoxetine and also synergistic effects with fluoxetine in forced swimming test, which implicates these compounds can be developed to help the treatment of major depressive disorder.

The neuropharmacology of sleep paralysis hallucinations: serotonin 2A activation and a novel therapeutic drug.

Sleep paralysis is a state of involuntary immobility occurring at sleep onset or offset, often accompanied by uncanny "ghost-like" hallucinations and extreme fear reactions. I provide here a neuropharmacological account for these hallucinatory experiences by evoking the role of the serotonin 2A receptor (5-HT2AR). Research has shown that 5-HT2AR activation can induce visual hallucinations, "mystical" subjective states, and out-of-body experiences (OBEs), and modulate fear circuits. Hallucinatory experiences triggered by serotonin-serotonergic ("pseudo") hallucinations, induced by hallucinogenic drugs-tend to be "dream-like" with the experiencer having insight ("meta-awareness") that he is hallucinating, unlike dopaminergic ("psychotic" and "life-like") hallucinations where such insight is lost. Indeed, hallucinatory experiences during sleep paralysis have the classic features of serotonergic hallucinations, and are strikingly similar to perceptual and subjective states induced by hallucinogenic drugs (e.g., lysergic acid diethylamide [LSD] and psilocybin), i.e., they entail visual hallucinations, mystical experiences, OBEs, and extreme fear reactions. I propose a possible mechanism whereby serotonin could be functionally implicated in generating sleep paralysis hallucinations and fear reactions through 5-HT2AR activity. Moreover, I speculate on the role of 5-HT2C receptors vis-à-vis anxiety and panic during sleep paralysis, and the orbitofrontal cortex-rich with 5-HT2A receptors-in influencing visual pathways during sleep paralysis, and, in effect, hallucinations. Finally, I propose, for the first time, a drug to target sleep paralysis hallucinations and fear reactions, namely the selective 5-HT2AR inverse agonist, pimavanserin. This account implicates gene HTR2A on chromosome 13q as the underlying cause of sleep paralysis hallucinations and could be explored using positron emission tomography.

Changes in global and thalamic brain connectivity in LSD-induced altered states of consciousness are attributable to the 5-HT2A receptor.

Background: Lysergic acid diethylamide (LSD) has agonist activity at various serotonin (5-HT) and dopamine receptors. Despite the therapeutic and scientific interest in LSD, specific receptor contributions to its neurobiological effects remain unknown. Methods: We therefore conducted a double-blind, randomized, counterbalanced, cross-over studyduring which 24 healthy human participants received either (i) placebo+placebo, (ii) placebo+LSD (100 µg po), or (iii) Ketanserin, a selective 5-HT2A receptor antagonist,+LSD. We quantified resting-state functional connectivity via a data-driven global brain connectivity method and compared it to cortical gene expression maps. Results: LSD reduced associative, but concurrently increased sensory-somatomotor brain-wide and thalamic connectivity. Ketanserin fully blocked the subjective and neural LSD effects. Whole-brain spatial patterns of LSD effects matched 5-HT2A receptor cortical gene expression in humans. Conclusions: Together, these results strongly implicate the 5-HT2A receptor in LSD's neuropharmacology. This study therefore pinpoints the critical role of 5-HT2A in LSD's mechanism, which informs its neurobiology and guides rational development of psychedelic-based therapeutics. Funding: Funded by the Swiss National Science Foundation, the Swiss Neuromatrix Foundation, the Usona Institute, the NIH, the NIAA, the NARSAD Independent Investigator Grant, the Yale CTSA grant, and the Slovenian Research Agency. Clinical trial number: NCT02451072

The psychedelic drug LSD alters thinking and perception. Users can experience hallucinations, in which they, for example, see things that are not there. Colors, sounds and objects can appear distorted, and time can seem to speed up or slow down. These changes bear some resemblance to the changes in thinking and perception that occur in certain psychiatric disorders, such as schizophrenia. Studying how LSD affects the brain could thus offer insights into the mechanisms underlying these conditions. There is also evidence that LSD itself could help to reduce the symptoms of depression and anxiety disorders. Preller et al. have now used brain imaging to explore the effects of LSD on the brains of healthy volunteers. This revealed that LSD reduced communication among brain areas involved in planning and decision-making, but it increased communication between areas involved in sensation and movement. Volunteers whose brains showed the most communication between sensory and movement areas also reported the strongest effects of LSD on their thinking and perception. Preller et al. also found that another drug called Ketanserin prevented LSD from altering how different brain regions communicate. It also prevented LSD from inducing changes in thinking and perception. Ketanserin blocks a protein called the serotonin 2A receptor, which is activated by a brain chemical called serotonin that, amongst other roles, helps to regulate mood. By mapping the location of the gene that produces the serotonin 2A receptor, Preller et al. showed that the receptor is present in brain regions that show altered communication after LSD intake, therefore pinpointing the importance of this receptor in the effects of LSD. Psychiatric disorders that produce psychotic symptoms affect vast numbers of people worldwide. Further research into how LSD affects the brain could help us to better understand how such symptoms arise, and may also lead to the development of more effective treatments for a range of mental health conditions.

Pharmacological Characterization of H05, a Novel Serotonin and Noradrenaline Reuptake Inhibitor with Moderate 5-HT2A Antagonist Activity for the Treatment of Depression.

Multitarget antidepressants selectively inhibiting monoaminergic transporters and 5-hydroxytryptamine (5-HT) 2A receptor have demonstrated higher efficacy and fewer side effects than selective serotonin reuptake inhibitors. In the present study, we synthesized a series of novel 3-(benzo[d][1,3]dioxol-4-yloxy)-3-arylpropyl amine derivatives, among which compound H05 was identified as a lead, exhibiting potent inhibitory effects on both serotonin (Ki = 4.81 nM) and norepinephrine (NE) (Ki = 6.72 nM) transporters and moderate 5-HT2A antagonist activity (IC50 = 60.37 nM). H05 was able to dose-dependently reduce the immobility duration in mouse forced swimming test and tail suspension test, with the minimal effective doses lower than those of duloxetine, and showed no stimulatory effect on locomotor activity. The administration of H05 (5, 10, and 20 mg/kg, by mouth) significantly shortened the immobility time of adrenocorticotropin-treated rats that serve as a model of treatment-resistant depression, whereas imipramine (30 mg/kg, by mouth) and duloxetine (30 mg/kg, by mouth) showed no obvious effects. Chronic treatment with H05 reversed the depressive-like behaviors in a rat model of chronic unpredictable mild stress and a mouse model of corticosterone-induced depression. Microdialysis analysis revealed that the administration of H05 at either 10 or 20 mg/kg increased the release of 5-HT and NE from the frontal cortex. The pharmacokinetic (PK) and brain penetration analyses suggest that H05 has favorable PK properties with good blood-brain penetration ability. Therefore, it can be concluded that H05, a novel serotonin and NE reuptake inhibitor with 5-HT2A antagonist activity, possesses efficacious activity in the preclinical models of depression and treatment-resistant depression, and it may warrant further evaluation for clinical development.

Effects of different serotonin receptor subtype antagonists on the development of cardiac allograft vasculopathy in murine aortic allografts.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is the main obstacle for long-term survival after heart transplantation. Alloimmune mediated chronic vascular rejection results in several mechanisms like platelet activation, immigration of inflammatory cells through the endothelial layer and proliferation and migration of smooth muscle cells (SMCs). Serotonin (5-HT) promotes these processes via activation of 5-HT2 receptors. We hypothesized that inhibiting 5-HT2 receptors ameliorates the development of CAV. METHODS: CBA/JRj mice recieved aortic grafts from C57BL/6 mice. After transplantation until recovery of organs, recipients were treated with serotonin receptor antagonists: sarpogrelate (5-HT2A), SB 204741 (5-HT2B) or terguride (5-HT2A+B). Mice were sacrificed after 14 days for qRT-PCR analysis or after 30 days for histological evaluation. Serum serotonin ELISA was done at both time points. RESULTS: Elevated serum serotonin levels were significantly reduced after 5-HT2A antagonist treatment as was 5-HT2A receptor expression. This went along with reduced inflammation characterized by significantly fewer infiltrating macrophages and pro-inflammatory intragraft cytokines and with reduced tissue remodeling evident as significantly less neointima formation. CONCLUSION: Inhibition of the 5HT/5-HT2A receptor axis leads to significantly reduced neointima proliferation after aortic transplantation associated with reduced transendothelial migration of macrophages and decreased expression of inflammatory cytokines. These findings have translational implications as inhibitors of 5HT2A like sarpogrelate are already approved for clinical use.

Synthesis and biological evaluation of a series of novel pyridinecarboxamides as potential multi-receptor antipsychotic drugs.

In previous study, a series of benzamides was identified as potent antipsychotic agents. As a continuation of the program to discover novel antipsychotics, herein we reported the evaluation of a series of pyridinecarboxamide derivatives. The most promising compound 7h not only held good activities on dopamine D2, serotonin 5-HT1A and 5-HT2A receptors, but also exhibited low potency for α1A, H1 and 5-HT2C receptors, indicating a low propensity of side effects like orthostatic hypotension and weight gain. Furthermore, 7h exhibited more potent antipsychotic-like effect than aripiprazole in behavioral studies. The preliminary results were promising enough for further research around this scaffold.

Homology Modeling Inspired Synthesis of 5-HT2A Receptor Inhibitors: A Diazepine Analogue of the Atypical Antipsychotic JL13.

BACKGROUND: The benzoxazepine JL13 is an analogue of the clozapine family of antipsychotic agents which target the 5-HT2A receptor, and has showed promise as an atypical antipsychotic agent. Based on the dearth of clinically effective anti-psychotic agents available, we sought to design and chemically synthesize additional analogues. METHODS: Structure function analysis was conducted using state of art computational methods, which were designed to highlight new candidates for chemical synthesis. Efficient syntheses were then conducted and the products screened for affinity to the receptor. RESULTS: Among many new analogues prepared, an aza analogue demonstrated seventeen times greater affinity for the receptor than JL13. CONCLUSION: An efficient synthetic route to an aza-analogue of JL13 was developed and will allow rapid modifications of the core and synthesis of related libraries.

A short history of the 5-HT2C receptor: from the choroid plexus to depression, obesity and addiction treatment.

This paper is a personal account on the discovery and characterization of the 5-HT2C receptor (first known as the 5-HT1C receptor) over 30 years ago and how it translated into a number of unsuspected features for a G protein-coupled receptor (GPCR) and a diversity of clinical applications. The 5-HT2C receptor is one of the most intriguing members of the GPCR superfamily. Initially referred to as 5-HT1CR, the 5-HT2CR was discovered while studying the pharmacological features and the distribution of [3H]mesulergine-labelled sites, primarily in the brain using radioligand binding and slice autoradiography. Mesulergine (SDZ CU-085), was, at the time, best defined as a ligand with serotonergic and dopaminergic properties. Autoradiographic studies showed remarkably strong [3H]mesulergine-labelling to the rat choroid plexus. [3H]mesulergine-labelled sites had pharmacological properties different from, at the time, known or purported 5-HT receptors. In spite of similarities with 5-HT2 binding, the new binding site was called 5-HT1C because of its very high affinity for 5-HT itself. Within the following 10 years, the 5-HT1CR (later named 5-HT2C) was extensively characterised pharmacologically, anatomically and functionally: it was one of the first 5-HT receptors to be sequenced and cloned. The 5-HT2CR is a GPCR, with a very complex gene structure. It constitutes a rarity in the GPCR family: many 5-HT2CR variants exist, especially in humans, due to RNA editing, in addition to a few 5-HT2CR splice variants. Intense research led to therapeutically active 5-HT2C receptor ligands, both antagonists (or inverse agonists) and agonists: keeping in mind that a number of antidepressants and antipsychotics are 5-HT2CR antagonists/inverse agonists. Agomelatine, a 5-HT2CR antagonist is registered for the treatment of major depression. The agonist Lorcaserin is registered for the treatment of aspects of obesity and has further potential in addiction, especially nicotine/ smoking. There is good evidence that the 5-HT2CR is involved in spinal cord injury-induced spasms of the lower limbs, which can be treated with 5-HT2CR antagonists/inverse agonists such as cyproheptadine or SB206553. The 5-HT2CR may play a role in schizophrenia and epilepsy. Vabicaserin, a 5-HT2CR agonist has been in development for the treatment of schizophrenia and obesity, but was stopped. As is common, there is potential for further indications for 5-HT2CR ligands, as suggested by a number of preclinical and/or genome-wide association studies (GWAS) on depression, suicide, sexual dysfunction, addictions and obesity. The 5-HT2CR is clearly affected by a number of established antidepressants/antipsychotics and may be one of the culprits in antipsychotic-induced weight gain.

Development of a Multiplex Assay for Studying Functional Selectivity of Human Serotonin 5-HT2A Receptors and Identification of Active Compounds by High-Throughput Screening.

G protein-coupled receptors (GPCRs) exist as collections of conformations in equilibrium, and the efficacy of drugs has been proposed to be associated with their absolute and relative affinities for these different conformations. The serotonin 2A (5-HT2A) receptor regulates multiple physiological functions, is involved in the pathophysiology of schizophrenia, and serves as an important target of atypical antipsychotic drugs. This receptor was one of the first GPCRs for which the functional selectivity phenomenon was observed, with its various ligands exerting differential effects on the phospholipase A2 (PLA2) and phospholipase C (PLC) signaling pathways. We aimed to develop a multiplex functional assay in 96-well plates for the simultaneous measurement of the PLA2 and PLC pathways coupled to 5-HT2A receptors; this approach enables the detection of either functional selectivity or cooperativity phenomena in early drug screening stages. The suitability of the method for running screening campaigns was tested using the Prestwick Chemical Library, and 22 confirmed hits with activities of more than 90% were identified; 11 of these hits produced statistically significant differences between the two effector pathways. Thus, we have developed a miniaturized multiplex assay in 96-well plates to measure functional selectivity for 5-HT2A receptors in the early stages of the drug discovery process.

Serotonin 2A receptor agonist binding in the human brain with [(11)C]Cimbi-36: Test-retest reproducibility and head-to-head comparison with the antagonist [(18)F]altanserin.

INTRODUCTION: [(11)C]Cimbi-36 is a recently developed serotonin 2A (5-HT2A) receptor agonist positron emission tomography (PET) radioligand that has been successfully applied for human neuroimaging. Here, we investigate the test-retest variability of cerebral [(11)C]Cimbi-36 PET and compare [(11)C]Cimbi-36 and the 5-HT2A receptor antagonist [(18)F]altanserin. METHODS: Sixteen healthy volunteers (mean age 23.9 ± 6.4years, 6 males) were scanned twice with a high resolution research tomography PET scanner. All subjects were scanned after a bolus of [(11)C]Cimbi-36; eight were scanned twice to determine test-retest variability in [(11)C]Cimbi-36 binding measures, and another eight were scanned after a bolus plus constant infusion with [(18)F]altanserin. Regional differences in the brain distribution of [(11)C]Cimbi-36 and [(18)F]altanserin were assessed with a correlation of regional binding measures and with voxel-based analysis. RESULTS: Test-retest variability of [(11)C]Cimbi-36 non-displaceable binding potential (BPND) was consistently <5% in high-binding regions and lower for reference tissue models as compared to a 2-tissue compartment model. We found a highly significant correlation between regional BPNDs measured with [(11)C]Cimbi-36 and [(18)F]altanserin (mean Pearson's r: 0.95 ± 0.04) suggesting similar cortical binding of the radioligands. Relatively higher binding with [(11)C]Cimbi-36 as compared to [(18)F]altanserin was found in the choroid plexus and hippocampus in the human brain. CONCLUSIONS: Excellent test-retest reproducibility highlights the potential of [(11)C]Cimbi-36 for PET imaging of 5-HT2A receptor agonist binding in vivo. Our data suggest that Cimbi-36 and altanserin both bind to 5-HT2A receptors, but in regions with high 5-HT2C receptor density, choroid plexus and hippocampus, the [(11)C]Cimbi-36 binding likely represents binding to both 5-HT2A and 5-HT2C receptors.

Blonanserin extensively occupies rat dopamine D3 receptors at antipsychotic dose range.

Antagonism of the dopamine D3 receptor has been hypothesized to be beneficial for schizophrenia cognitive deficits, negative symptoms and extrapyramidal symptoms. However, recent animal and human studies have shown that most antipsychotics do not occupy D3 receptors in vivo, despite their considerable binding affinity for this receptor in vitro. In the present study, we investigated the D3 receptor binding of blonanserin, a dopamine D2/D3 and serotonin 5-HT2A receptors antagonist, in vitro and in vivo. Blonanserin showed the most potent binding affinity for human D3 receptors among the tested atypical antipsychotics (risperidone, olanzapine and aripiprazole). Our GTPγS-binding assay demonstrated that blonanserin acts as a potent full antagonist for human D3 receptors. All test-drugs exhibited antipsychotic-like efficacy in methamphetamine-induced hyperactivity in rats. Treatment with blonanserin at its effective dose blocked the binding of [(3)H]-(+)-PHNO, a D2/D3 receptor radiotracer, both in the D2 receptor-rich region (striatum) and the D3 receptor-rich region (cerebellum lobes 9 and 10). On the other hand, the occupancies of other test-drugs for D3 receptors were relatively low. In conclusion, we have shown that blonanserin, but not other tested antipsychotics, extensively occupies D3 receptors in vivo in rats.

New arylpiperazinylalkyl derivatives of 8-alkoxy-purine-2,6-dione and dihydro[1,3]oxazolo[2,3-f]purinedione targeting the serotonin 5-HT1A /5-HT2A /5-HT7 and dopamine D2 receptors.

To obtain potential antidepressants and/or antipsychotics, a series of new long-chain arylpiperazine derivatives of 8-alkoxy-purine-2,6-dione (10-24) and dihydro[1,3]oxazolo[2,3-f]purinedione (30-34) were synthesized and their serotonin (5-HT1A , 5-HT2A , 5-HT6 , 5-HT7 ) and dopamine (D2 ) receptor affinities were determined. The study allowed the identification of some potent 5-HT1A /5-HT7 /D2 ligands with moderate affinity for 5-HT2A sites. The binding mode of representative compounds from both chemical classes (11 and 31) in the site of 5-HT1A receptor was analyzed in computational studies. In functional in vitro studies, the selected compounds 15 and 16 showed antagonistic properties for the evaluated receptors. 8-Methoxy-7-{4-[4-(2-methoxyphenyl)-piperazin-1-yl]-butyl}-1,3-dimethyl-purine-2,6-dione (15) showed a lack of activity in terms and under the conditions of the forced swim, four plate and amphetamine-induced hyperactivity tests in mice, probably as a result of its high first pass effect in the liver.

BF-1--a novel selective 5-HT2B receptor antagonist blocking neurogenic dural plasma protein extravasation in guinea pigs.

Serotonin 5-HT2B receptor antagonists have been proposed as migraine prophylactic drugs, but previously available 5-HT2B receptor antagonists displayed multiple monoaminergic side effects and had to be withdrawn from the market. Here, we set out to identify a novel antagonist with high affinity and selectivity towards 5-HT2B receptors. To test the affinity of new compounds towards various receptors, we generated a broad series of cells functionally coupling human monoaminergic receptors to luciferase. Using the cell lines we revealed pimethixene (1-methyl-4-(9H-thioxanthen-9-ylidene)piperidine) as highly potent, albeit non-selective 5-HT2B receptor antagonist and optimized its chemical structure to create highly potent and selective 5-HT2B receptor antagonists. We selected the methoxythioxanthene BF-1 for further analysis. In comparison to pimethixene, it lacked high affinities to 5-HT1A, 5-HT2A, 5-HT2C, histamine H1, dopamine D1 and D2 as well as muscarinic M1 and M2 receptors. BF-1 was tested as potential migraine prophylactic drug by blocking meta-chlorophenylpiperazine, (mCPP) or BW723C86 (5-((thiophen-2-yl)methoxy)-α-methyltryptamine) induced neurogenic dural plasma protein extravasation in a guinea pig model that may resemble a migraine attack. BF-1 was significantly more potent in this assay compared to the well know non-selective 5-HT2B antagonists, methysergide ((6aR,9R)-N-[(2S)-1-Hydroxybutan-2-yl]-4,7-dimethyl-6,6a,8,9-tetrahydroindolo[4,3-fg]quinoline-9-carboxamide) or pizotifen (4-(1-methyl-4-piperidylidine)-9,10-dihydro-4H-benzo-[4,5]cyclohepta[1,2]-thiophene). Therefore, we propose BF-1 as a new compound that may be developed for prophylactic migraine treatment without the typical monoaminergic side effects.

Multidimensional de†novo design reveals 5-HT2B receptor-selective ligands.

We report a multi-objective de novo design study driven by synthetic tractability and aimed at the prioritization of computer-generated 5-HT2B receptor ligands with accurately predicted target-binding affinities. Relying on quantitative bioactivity models we designed and synthesized structurally novel, selective, nanomolar, and ligand-efficient 5-HT2B modulators with sustained cell-based effects. Our results suggest that seamless amalgamation of computational activity prediction and molecular design with microfluidics-assisted synthesis enables the swift generation of small molecules with the desired polypharmacology.

Pharmacology of hallucinations: several mechanisms for one single symptom?

Hallucinations are complex misperceptions, that principally occur in schizophrenia or after intoxication induced by three main classes of drugs: psychostimulants, psychedelics, and dissociative anesthetics. There are at least three different pharmacological ways to induce hallucinations: (1) activation of dopamine D2 receptors (D2Rs) with psychostimulants, (2) activation of serotonin 5HT2A receptors (HT2ARs) with psychedelics, and (3) blockage of glutamate NMDA receptors (NMDARs) with dissociative anesthetics. In schizophrenia, the relative importance of NMDAR and D2R in the occurrence of hallucinations is still debated. Slight clinical differences are observed for each etiology. Thus, we investigated whether the concept of hallucination is homogenous, both clinically and neurobiologically. A narrative review of the literature is proposed to synthesize how the main contributors in the field have approached and tried to solve these outstanding questions. While some authors prefer one explanatory mechanism, others have proposed more integrated theories based on the different pharmacological psychosis models. In this review, such theories are discussed and faced with the clinical data. In addition, the nosological aspects of hallucinations and psychosis are addressed. We suggest that if there may be common neurobiological pathways between the different pharmacological systems that are responsible for the hallucinations, there may also be unique properties of each system, which explains the clinical differences observed.

5-Hydroxy-2-(2-phenylethyl)chromone (5-HPEC): a novel non-nitrogenous ligand for 5-HT2B receptor.

Chromones are a class of natural products found in almost every known terrestrial plant with over 4000 naturally occurring derivatives having been isolated and structurally elucidated. Recently, 5-hydroxy-2-(2-phenylethyl)chromone (5-HPEC), isolated from Imperata cylindrical, showed neuroprotective activity against glutamate induced excitotoxicity in primary cultures of rat cortical cells. In comparison to other naturally occurring neuroprotective chromones, 5-HPEC contains fewer hydroxyl groups. Here we report our most recent characterization on this interesting natural product against a number of CNS receptors for the purpose to identify the potential molecular targets that may be related to its biological activity. Based on our studies, including radiobinding assays, calcium flux functional assays and molecular modeling studies, 5-HPEC may represent a type of novel nonnitrogenous ligands to the 5-HT2B receptor.