Affinity For Serotonin Transporter Research Articles

Dopamine in major depressive disorder: A systematic review and meta-analysis of in vivo imaging studies.

Major depressive disorder (MDD) is a leading cause of global disability. Several lines of evidence implicate the dopamine system in its pathophysiology. However, the magnitude and consistency of the findings are unknown. We address this by systematically reviewing in vivo imaging evidence for dopamine measures in MDD and meta-analysing these where there are sufficient studies. Studies investigating the dopaminergic system using positron emission tomography or single photon emission computed tomography in MDD and a control group were included. Demographic, clinical and imaging measures were extracted from each study, and meta-analyses and sensitivity analyses were conducted. We identified 43 studies including 662 patients and 801 controls. Meta-analysis of 38 studies showed no difference in mean or mean variability of striatal D2/3 receptor availability (g = 0.06, p = 0.620), or combined dopamine synthesis and release capacity (g = 0.19, p = 0.309). Dopamine transporter (DAT) availability was lower in the MDD group in studies using DAT selective tracers (g = -0.56, p = 0.006), but not when tracers with an affinity for serotonin transporters were included (g = -0.21, p = 0.420). Subgroup analysis showed greater dopamine release (g = 0.49, p = 0.030), but no difference in dopamine synthesis capacity (g = -0.21, p = 0.434) in the MDD group. Striatal D1 receptor availability was lower in patients with MDD in two studies. The meta-analysis indicates striatal DAT availability is lower, but D2/3 receptor availability is not altered in people with MDD compared to healthy controls. There may be greater dopamine release and lower striatal D1 receptors in MDD, although further studies are warranted. We discuss factors associated with these findings, discrepancies with preclinical literature and implications for future research.

Synthesis and biological evaluation of novel 3-(5-substituted-1H-indol-3-yl)pyrrolidine-2,5-dione derivatives with a dual affinity for serotonin 5-HT1A receptor and SERT

The serotonin 1A (5-HT1A) receptors and serotonin transporter (SERT) are important biological targets in the treatment of diseases of the central nervous system, especially for depression. In this study, new 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives linked with the 3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole moiety were synthesised and evaluated for their affinity for 5-HT1A receptor and serotonin reuptake inhibition. Selected compounds were then tested for their affinity for D2, 5-HT2A, 5-HT6 and 5-HT7 receptors, and also in in vitro metabolic stability assays in human microsomes. Finally, in vivo assays allowed us to evaluate the agonist–antagonist properties of pre- and postsynaptic 5-HT1A receptors. 3-(1-(4-(3-(5-methoxy-1H-indol-3-yl)-2,5-dioxopyrrolidin-1-yl)butyl)-1,2,3,6-tetrahydropyridin-4-yl)-1H-indole-5-carbonitrile (4f) emerged as the most promising compound from the series, due to its favourable receptor binding profile (Ki(5-HT1A) = 10.0 nM; Ki(SERT) = 2.8 nM), good microsomal stability and 5-HT1A receptor agonistic activity.

Use of Antidepressants and the Risk of Upper Gastrointestinal Tract Bleeding: A Case-control Study

PurposeTo investigate the association between the use of antidepressants and the risk of upper gastrointestinal tract bleeding (UGIB). MethodsA Case-control study was conducted in a Brazilian hospital complex. Cases were defined as patients with a diagnosis of UGIB and controls as patients admitted for reasons unrelated to gastrointestinal bleeding, gastric concerns, or complications associated with low-dose aspirin (LDA) or nonsteroidal anti-inflammatory drugs (NSAIDs) use. Sociodemographic and clinical data, comorbidities, drug therapy in use (long-term use and self-medication), and lifestyle habits were recorded through face-to-face interviews. Two groups were defined: use of antidepressants in general and use of antidepressants according to their affinity for serotonin transporters. The presence of synergism between the concomitant use of antidepressants and LDA or NSAIDs on the risk of UGIB was also explored. FindingsA total of 906 participants were recruited (200 in the case group and 706 in the control group). The use of antidepressants was not associated with the risk of UGIB (odds ratio [OR] = 1.503; 95% CI, 0.78–2.88) or the use of antidepressants with high affinity for serotonin receptors (OR = 1.983; 95% CI, 0.81–4.85). An increased risk of UGIB was observed in concomitant users of antidepressants and LDA (OR = 5.489; 95% CI, 1.60–18.81) or NSAIDs (OR = 18.286; 95% CI, 3.18–105.29). Despite the lack of significance, the use of antidepressants appears to be a positive modifier of UGIB risk in LDA and NSAID users. ImplicationsThese findings indicate an increased risk of UGIB in concomitant users of antidepressants and LDA or NSAIDs, suggesting the need to monitor antidepressant users, especially those most likely to develop UGIB. In addition, further studies with larger sample sizes are needed to confirm these findings.

Pharmacologic Activity of Substituted Tryptamines at 5-Hydroxytryptamine (5-HT)2A Receptor (5-HT2AR), 5-HT2CR, 5-HT1AR, and Serotonin Transporter.

Novel psychoactive substances, including synthetic substituted tryptamines, represent a potential public health threat. Additionally, some substituted tryptamines are being studied under medical guidance as potential treatments of psychiatric disorders. Characterizing the basic pharmacology of substituted tryptamines will aid in understanding differences in potential for harm or therapeutic use. Using human embryonic kidney cells stably expressing 5-hydroxytryptamine (5-HT)1A, 5-HT2A, and 5-HT2C receptors (5-HT1AR, 5-HT2AR, and 5HT2CR, respectively) or the serotonin transporter (SERT), we measured affinities, potencies and efficacies of 21 substituted tryptamines. With the exception of two 4-acetoxy compounds, substituted tryptamines exhibited affinities and potencies less than one micromolar at the 5-HT2AR, the primary target for psychedelic effects. In comparison, half or more exhibited low affinities/potencies at 5-HT2CR, 5-HT1AR, and SERT. Sorting by the ratio of 5-HT2A to 5-HT2C, 5-HT1A, or SERT affinity revealed chemical determinants of selectivity. We found that although 4-substituted compounds exhibited affinities that ranged across a factor of 100, they largely exhibited high selectivity for 5-HT2ARs versus 5-HT1ARs and 5-HT2CRs. 5-substituted compounds exhibited high affinities for 5-HT1ARs, low affinities for 5-HT2CRs, and a range of affinities for 5-HT2ARs, resulting in selectivity for 5-HT2ARs versus 5-HT2CRs but not versus 5-HT1ARs. Additionally, a number of psychedelics bound to SERT, with non-ring-substituted tryptamines most consistently exhibiting binding. Interestingly, substituted tryptamines and known psychedelic standards exhibited a broad range of efficacies, which were lower as a class at 5-HT2ARs compared with 5-HT2CRs and 5-HT1ARs. Conversely, coupling efficiency/amplification ratio was highest at 5-HT2ARs in comparison with 5-HT2CRs and 5-HT1ARs. SIGNIFICANCE STATEMENT: Synthetic substituted tryptamines represent both potential public health threats and potential treatments of psychiatric disorders. The substituted tryptamines tested differed in affinities, potencies, and efficacies at 5-hydroxytryptamine (5-HT)2A, 5-HT2C, and 5HT1A receptors and the serotonin transporter (SERT). Several compounds were highly selective for and coupled very efficiently downstream of 5-HT2A versus 5-HT1A and 5-HT2C receptors, and some bound SERT. This basic pharmacology of substituted tryptamines helps us understand the pharmacologic basis of their potential for harm and as therapeutic agents.

Selective serotonin reuptake inhibitors and the risk of type 2 diabetes mellitus in youths

BackgroundSelective serotonin reuptake inhibitors (SSRIs) have been associated with type 2 diabetes mellitus (T2DM) in youths, possibly via 5-HT2C, H1 receptors and serotonin transporter (SERT). SSRIs have similar affinity for SERT but variable affinity for 5-HT2C and H1. This study assessed whether SSRIs with strong affinity for 5-HT2C and H1 (relative to SERT) were associated with T2DM risk compared with weak-affinity SSRIs. MethodsUsing the UK Clinical Practice Research Datalink, we assembled a cohort of patients aged 5–24, newly prescribed a strong-affinity SSRI (citalopram, escitalopram, fluoxetine) or weak affinity (paroxetine, sertraline, fluvoxamine) between 1990 and 2019. We controlled for confounding using standardized mortality ratio weighting, estimated from calendar time-specific propensity scores. We used weighted Cox proportional hazards models to estimate hazard ratios (HRs) of incident T2DM with 95 % confidence intervals (CIs). ResultsThe cohort included 347,368 new users of strong-affinity SSRIs and 131,359 of weak-affinity SSRIs. Strong-affinity SSRIs were not associated with an increased T2DM risk compared with weak-affinity SSRIs (incidence rate 2.8 vs 2.7 per 1000 person-years; HR 1.03, 95 % CI 0.85–1.25). T2DM risk did not vary with duration of use, age or sex. However, the HR was numerically higher in youths with normal or low weight (HR 1.30, 95 % CI 0.85–1.98) and with prior antipsychotic use (HR 1.62, 95 % CI 0.83–3.18). LimitationsMedian duration of SSRI use, in line with real-world SSRI prescribing, was relatively short. ConclusionT2DM risk did not differ between strong- and weak-affinity SSRIs, providing reassurance for clinicians when choosing between SSRIs in youths.

Impact of serotonin transporter (SERT) binding affinity on the risk of libido disorders related to antidepressants

IntroductionSexual dysfunction is a frequent adverse drug reaction (ADR) of antidepressants that considerably affects quality of life and adherence to therapy. We previously investigated the potential underlying neurofunctional mechanisms by neuroimaging methods and revealed a dampening of the dopaminergic mesolimbic-mesocortical reward system along with decreased sexual functioning under serotonergic antidepressants compared to placebo.ObjectivesWithin a combined pharmacoepidemiologic and pharmacodynamic approach, we examined the association between serotonin transporter (SERT) affinity of various antidepressants and corresponding alterations in sexual desire as ADR.MethodsUsing disproportionality analyses, reporting odds ratios (RORs) were calculated for reports indicating decreased sexual desire as ADR under the antidepressants. The data were extracted from the WHO global database of individual case safety reports VigiBase and several MedDRA terms were grouped for “Sexual Desire Disorders”. For the pharmacodynamic assessment, we calculated Pearson correlation coefficients between SERT affinity and corresponding RORsResults16 signals were detected for “Sexual Desire Disorders”. We observed a statistically significant (r (20) =. 65, p = 0.001) association between SERT affinity and decreased sexual desire. Higher SERT affinity was associated with higher risk of sexual desire.ConclusionsWhile sexual dysfunctions under serotonergic medication were previously described, we now elaborated that in particular attenuated sexual desire as ADR is associated with SERT affinity of the antidepressant. These results strengthen our previously described neurofunctional model regarding sexual dysfunction under antidepressant medication and indicate that the specific SERT affinity of the antidepressant drug should be considered in clinical practice to minimize the risk of this ADR.DisclosureNo significant relationships.

Modafinil acquires reinforcing effects when combined with citalopram

Modafinil (MOD) is a wakefulness promoter used to treat sleep disorders such as narcolepsy and obstructive sleep apnea. Its action mechanism consists in inhibiting dopamine (DAT) and norepinephrine (NET) transporters, but it has no affinity for the serotonin transporter (SERT). Modafinil's addictive potential is not yet clear, but one feature that differentiates it from potentially addictive drugs like cocaine revolves around affinity for SERT. The aims of the present study were to determine whether co-administration of MOD with the selective serotonin reuptake inhibitor citalopram (CIT) can increase MOD's psychostimulant effects on motor activity (MA), verify the effects of subsequent self-administration of MOD mixed with CIT, and document the presence of any symptoms of withdrawal. At 60 postnatal days (PD), male Wistar rats were treated chronically (16 days) with MOD at 30 or 60 mg/kg, with MOD+CIT at four dosage combinations administered to four groups (30MOD + CIT3, 30MOD + CIT5, 60MOD + CIT3, 60MOD + CIT5 mg/kg), or with a vehicle. After 40 min of daily drug administration, MA was measured on the open field test. MA increased only in the 60MOD group. The rats co-administered with 30MOD + 3CIT and 60MOD + 3CIT showed a decrease in the motivation to seek a pleasurable stimulus (lower consumption of sweet solution) after treatment concluded. The 60MOD and 60MOD + 3CIT groups showed MA sensitization after MOD intake. Additionally, higher self-administration of the mixture was observed in the groups pre-treated with 30MOD + 3CIT and 60MOD + 3CIT. Results suggest that serotonergic activity enhances modafinil's psychostimulant effects.

Identifying Antidepressants Less Likely to Cause Hyponatremia: Triangulation of Retrospective Cohort, Disproportionality, and Pharmacodynamic Studies.

Antidepressants are known to cause hyponatremia, but conflicting evidence exists regarding specific antidepressants. To identify antidepressants less likely to cause hyponatremia, we conducted a triangulation study integrating retrospective cohort, disproportionality, and pharmacodynamic studies. In the retrospective cohort study of patients (≥ 60 years) in Nihon University School of Medicine’s Clinical Data Warehouse (2004–2020), a significant decrease in serum sodium levels was observed within 30 days after initiation of a selective serotonin reuptake inhibitor (SSRI; mean change −1.00 ± 0.23 mmol/L, P < 0.001) or serotonin‐noradrenaline reuptake inhibitor (SNRI; −1.01 ± 0.31 mmol/L, P = 0.0013), whereas no decrease was found for a noradrenergic and specific serotonergic antidepressant (mirtazapine; +0.55 ± 0.47 mmol/L, P = 0.24). Within‐class comparison revealed no decrease in serum sodium levels for fluvoxamine (+0.74 ± 0.75 mmol/L, P = 0.33) among SSRIs and milnacipran (+0.08 ± 0.87 mmol/L, P = 0.93) among SNRIs. In the disproportionality analysis of patients (≥ 60 years) in the Japanese Adverse Drug Event Report database (2004–2020), a significant increase in hyponatremia reports was observed for SSRIs (reporting odds ratio 4.41, 95% confidence interval 3.58–5.45) and SNRIs (5.66, 4.38–7.31), but not for mirtazapine (1.08, 0.74–1.58), fluvoxamine (1.48, 0.94–2.32), and milnacipran (0.85, 0.45–1.62). Finally, pharmacoepidemiological–pharmacodynamic analysis revealed a significant correlation between the decrease in serum sodium levels and binding affinity for serotonin transporter (SERT; r = −0.84, P = 0.02), suggesting that lower binding affinity of mirtazapine, fluvoxamine, and milnacipran against SERT is responsible for the above difference. Although further research is needed, our data suggest that mirtazapine, fluvoxamine, and milnacipran are less likely to cause hyponatremia.

Effects of Subchronic Administrations of Vortioxetine, Lurasidone, and Escitalopram on Thalamocortical Glutamatergic Transmission Associated with Serotonin 5-HT7 Receptor.

The functional suppression of serotonin (5-HT) type 7 receptor (5-HT7R) is forming a basis for scientific discussion in psychopharmacology due to its rapid-acting antidepressant-like action. A novel mood-stabilizing atypical antipsychotic agent, lurasidone, exhibits a unique receptor-binding profile, including a high affinity for 5-HT7R antagonism. A member of a novel class of antidepressants, vortioxetine, which is a serotonin partial agonist reuptake inhibitor (SPARI), also exhibits a higher affinity for serotonin transporter, serotonin receptors type 1A (5-HT1AR) and type 3 (5-HT3R), and 5-HT7R. However, the effects of chronic administration of lurasidone, vortioxetine, and the selective serotonin reuptake inhibitor (SSRI), escitalopram, on 5-HT7R function remained to be clarified. Thus, to explore the mechanisms underlying the clinical effects of vortioxetine, escitalopram, and lurasidone, the present study determined the effects of these agents on thalamocortical glutamatergic transmission, which contributes to emotional/mood perception, using multiprobe microdialysis and 5-HT7R expression using capillary immunoblotting. Acute local administration of a 5-HT7R agonist and antagonist into the mediodorsal thalamic nucleus (MDTN) enhanced and reduced thalamocortical glutamatergic transmission, induced by N-methyl-D-aspartate (NMDA)/glutamate receptor inhibition in the reticular thalamic nucleus (RTN). Acute local administration of a relevant therapeutic concentration of vortioxetine and lurasidone into the MDTN suppressed the thalamocortical glutamatergic transmission via 5-HT7R inhibition, whereas that of escitalopram activated 5-HT7R. Subchronic administration of effective doses of vortioxetine and lurasidone (for 7 days) reduced the thalamocortical glutamatergic transmission, but escitalopram did not affect it, whereas subchronic administration of these three agents attenuated the stimulatory effects of the 5-HT7R agonist on thalamocortical glutamatergic transmission. Subchronic administration of effective doses of vortioxetine, lurasidone, and escitalopram downregulated the 5-HT7R expression of the plasma membrane in the MDTN; the 5-HT7R downregulation induced by vortioxetine and lurasidone was observed at 3 days, but that induced by escitalopram required a longer duration of 7 days. These results indicate that chronic administration of vortioxetine, escitalopram, and lurasidone generate downregulation of 5-HT7R in the thalamus; however, the direct inhibition of 5-HT7R associated with vortioxetine and lurasidone generates more rapid downregulation than the indirect elevation of the extracellular serotonin level via serotonin transporter inhibition by escitalopram.

Synthesis, Docking, 3-D-Qsar, and Biological Assays of Novel Indole Derivatives Targeting Serotonin Transporter, Dopamine D2 Receptor, and Mao-A Enzyme: In the Pursuit for Potential Multitarget Directed Ligands.

A series of 27 compounds of general structure 2,3-dihydro-benzo[1,4]oxazin-4-yl)-2-{4-[3-(1H-3indolyl)-propyl]-1-piperazinyl}-ethanamides, Series I: 7(a–o) and (2-{4-[3-(1H-3-indolyl)-propyl]-1-piperazinyl}-acetylamine)-N-(2-morfolin-4-yl-ethyl)-fluorinated benzamides Series II: 13(a–l) were synthesized and evaluated as novel multitarget ligands towards dopamine D2 receptor, serotonin transporter (SERT), and monoamine oxidase-A (MAO-A) directed to the management of major depressive disorder (MDD). All the assayed compounds showed affinity for SERT in the nanomolar range, with five of them displaying Ki values from 5 to 10 nM. Compounds 7k, Ki = 5.63 ± 0.82 nM, and 13c, Ki = 6.85 ± 0.19 nM, showed the highest potencies. The affinities for D2 ranged from micro to nanomolar, while MAO-A inhibition was more discrete. Nevertheless, compounds 7m and 7n showed affinities for the D2 receptor in the nanomolar range (7n: Ki = 307 ± 6 nM and 7m: Ki = 593 ± 62 nM). Compound 7n was the only derivative displaying comparable affinities for SERT and D2 receptor (D2/SERT ratio = 3.6) and could be considered as a multitarget lead for further optimization. In addition, docking studies aimed to rationalize the molecular interactions and binding modes of the designed compounds in the most relevant protein targets were carried out. Furthermore, in order to obtain information on the structure–activity relationship of the synthesized series, a 3-D-QSAR CoMFA and CoMSIA study was conducted and validated internally and externally (q2 = 0.625, 0.523 for CoMFA and CoMSIA and r2ncv = 0.967, 0.959 for CoMFA and CoMSIA, respectively).

Selective serotonin reuptake inhibitors (SSRIs) prevent meta-iodobenzylguanidine (MIBG) uptake in platelets without affecting neuroblastoma tumor uptake

BackgroundThe therapeutic use of [131I]meta-iodobenzylguanidine ([131I]MIBG) is often accompanied by hematological toxicity, mainly consisting of persistent and severe thrombocytopenia. While MIBG accumulates in neuroblastoma cells via selective uptake by the norepinephrine transporter (NET), the serotonin transporter (SERT) is responsible for cellular uptake of MIBG in platelets. In this study, we have investigated whether pharmacological intervention with selective serotonin reuptake inhibitors (SSRIs) may prevent radiotoxic MIBG uptake in platelets without affecting neuroblastoma tumor uptake.MethodsTo determine the transport kinetics of SERT for [125I]MIBG, HEK293 cells were transfected with SERT and uptake assays were conducted. Next, a panel of seven SSRIs was tested in vitro for their inhibitory potency on the uptake of [125I]MIBG in isolated human platelets and in cultured neuroblastoma cells. We investigated in vivo the efficacy of the four best performing SSRIs on the accumulation of [125I]MIBG in nude mice bearing subcutaneous neuroblastoma xenografts. In ex vivo experiments, the diluted plasma of mice treated with SSRIs was added to isolated human platelets to assess the effect on [125I]MIBG uptake.ResultsSERT performed as a low-affinity transporter of [125I]MIBG in comparison with NET (Km = 9.7 μM and 0.49 μM, respectively). Paroxetine was the most potent uptake inhibitor of both serotonin (IC50 = 0.6 nM) and MIBG (IC50 = 0.2 nM) in platelets. Citalopram was the most selective SERT inhibitor of [125I]MIBG uptake, with high SERT affinity in platelets (IC50 = 7.8 nM) and low NET affinity in neuroblastoma cells (IC50 = 11.940 nM). The in vivo tested SSRIs (citalopram, fluvoxamine, sertraline, and paroxetine) had no effect on [125I]MIBG uptake levels in neuroblastoma xenografts. In contrast, treatment with desipramine, a NET selective inhibitor, resulted in profoundly decreased xenograft [125I]MIBG levels (p < 0.0001). In ex vivo [125I]MIBG uptake experiments, 100- and 34-fold diluted murine plasma of mice treated with citalopram added to isolated human platelets led to a decrease in MIBG uptake of 54–76%, respectively.ConclusionOur study demonstrates for the first time that SSRIs selectively inhibit MIBG uptake in platelets without affecting MIBG accumulation in an in vivo neuroblastoma model. The concomitant application of citalopram during [131I]MIBG therapy seems a promising strategy to prevent thrombocytopenia in neuroblastoma patients.

In vivo long-lasting alterations of central serotonin transporter activity and associated dopamine synthesis after acute repeated administration of methamphetamine

BackgroundMethamphetamine (METH)-associated alterations in the striatal dopamine (DA) system or dopamine transport (DAT) have been identified in clinical and preclinical studies with positron emission tomography (PET) imaging but have not been well correlated with in vivo serotonin transporter (SERT) availability due to the lack of appropriate imaging agents to assess SERTs. N,N-dimethyl-2-(2-amino-4-[18F]-fluorophenylthio) benzylamine (4-[18F]-ADAM) has been developed by our group and validated for its high affinity and selectivity for SERTs, allowing the in vivo examination of SERT density, location, and binding function. The aims of this study were to investigate the potential of SERT imaging using 4-[18F]-ADAM PET to estimate the long-lasting effects of METH-induced serotonergic neurotoxicity, and further determine whether a correlative relationship exists between SERT availability/activity and tyrosine hydroxylase (TH) activity in various brain regions due to the long-lasting consequences of METH treatment.ResultsMale rats received four administrations of METH (5 or 10 mg/kg, s.c.) or saline (1 ml/kg, s.c.) at 1-h intervals. At 30 days post-administration, in vivo SERT availability and activity were measured by 4-[18F]ADAM PET imaging. In contrast to the controls, the uptake of 4-[18F]ADAM in METH-treated mice was significantly reduced in a dose-dependent manner in the midbrain, followed by the hypothalamus, thalamus, striatum, hippocampus, and frontal cortex. The regional effects of METH on TH activity were assessed by quantitative immunohistochemistry and presented as integrated optical density (IOD). A significant decrease in TH immunostaining and IOD ratios was seen in the caudate, putamen, nucleus accumbens, substantia nigra pars compacta, and substantia nigra pars reticulata in the METH-treated rats compared to controls.ConclusionThe present results suggested that the long-lasting response to METH decreased the uptake of 4-[18F]-ADAM and varied regionally along with TH immunoreactivity. In addition, 4-[18F]ADAM PET could be used to detect serotonergic neuron loss and to evaluate the severity of serotonergic neurotoxicity of METH.

1,3,4‐thiadiazines as promising compounds acting on the serotonin turnover

According to the previous data, 1,3,4‐thiadiazines are able to reduce the stress reaction's magnitude and acts like the atypical neuroleptics. Thus, the aim of the present study was to analyze the influence of 1,3,4‐thiadiazine compound (L‐17) on the serotonin turnover in silico and in vivo.In silico studiesThe target proteins of in silico study included the serotonin receptor type 3A (5‐HT3A) and the serotonin transporter (SERT). For the evaluation of the L‐17 compound's affinity, the docking of the compound to the specific binding sites of these proteins was performed. Experimental X‐ray 3D models were obtained from Protein Data Bank in Europe. The 3‐D model of the L‐17 compound was constructed using the molecular mechanics methods in the MarvinSketch 15.6.15 program, followed by optimization with the semi‐empirical quantum chemical method PM7 in the MOPAC2016 program. The docking was performed using AutoDockVina 1.1.2.In vivo studiesAdult male Wistar rats (200–250 g) were housed in a temperature‐controlled room with a 12:12 hours light‐dark cycle. All experimental procedures were approved by the Animal Care and Use Committee and conformed to the Directive 2010/63/EU of the European Parliament. The rats received intravenous (i.p.) injections of L‐17 (0.1–12 mg/kg) dissolved in saline. Control animals were injected saline using the same protocol. One hour after the last saline or L‐17 injection, rats were anesthetized with chloral hydrate and mounted into the stereotaxic frame. The scalp was opened and a 3 mm hole was drilled in the skull for insertion of electrodes. Serotonin neurons were identified by their typical firing rate, positive bi‐ or tri‐phasic action potential and the cumulative duration of depolarization and repolarization phases, and recorded for at least two minutes using the Power Lab data acquisition system and Lab Chart software.ResultsAccording to the results of the in silico prediction, the values of the docking energy of the L‐17 compound in the binding sites for SERT were 8.1 and 8.3 kcal/mol for 5‐HT3A and SERT, respectively. Molecular docking revealed that the moderate serotonin‐blocking effect of L‐17 was due, above all, to a sufficiently high affinity for SERT; the direct antagonism to 5‐HT3A receptors was negligible. According to the electrophysiological study results, the mean basal firing activity was 3.46±0.83 Hz. L‐17 (0.1–12 mg/kg, i.v.) significantly and dose‐dependently (Fdf 8,53=4.84, p&lt;0.001, ANOVA for repeated measured) inhibited the firing activity of 5‐Ht neurons, reaching the maximal 90%‐ inhibition at 12 mg/kg. WAY100135 partially reversed the L17‐induced inhibition of 5‐HT neurons.Thus, the electrophysiological study confirmed the results of in silico prediction, identifying SERT as a potential biotarget of the promising compounds from the group of substituted 1,3,4‐thiadiazines.Support or Funding InformationThr study was supported by the Russian Science Foundation (project 17‐15‐01318)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Aromatic Bromination Abolishes the Psychomotor Features and Pro-social Responses of MDMA ("Ecstasy") in Rats and Preserves Affinity for the Serotonin Transporter (SERT).

The entactogen MDMA (3,4-methylenedioxy-methamphetamine, “Ecstasy”) exerts its psychotropic effects acting primarily as a substrate of the serotonin transporter (SERT) to induce a non-exocytotic release of serotonin. Nevertheless, the roles of specific positions of the aromatic ring of MDMA associated with the modulation of typical entactogenic effects, using analogs derived from the MDMA template, are still not fully understood. Among many possibilities, aromatic halogenation of the phenylalkylamine moiety may favor distribution to the brain due to increased lipophilicity, and sometimes renders psychotropic substances of high affinity for their molecular targets and high potency in humans. In the present work, a new MDMA analog brominated at C(2) of the aromatic ring (2-Br-4,5-MDMA) has been synthesized and pharmacologically characterized in vitro and in vivo. First, binding competition experiments against the SERT-blocker citalopram were carried out in human platelets and compared with MDMA. Besides, its effects on platelet aggregation were performed in platelet enriched human plasma using collagen as aggregation inductor. Second, as platelets are considered an appropriate peripheral model for estimating central serotonin availability, the functional effects of 2-Br-4,5-MDMA and MDMA on ATP release during human platelet aggregation were evaluated. The results obtained showed that 2-Br-4,5-MDMA exhibits higher affinity for SERT than MDMA and fully abolishes both platelet aggregation and ATP release, resembling the pharmacological profile of citalopram. Subsequent in vivo evaluation in rats at three dose levels showed that 2-Br-4,5-MDMA lacks all key MDMA-like behavioral responses in rats, including hyperlocomotion, enhanced active avoidance conditioning responses and increased social interaction. Taken together, the results obtained are consistent with the notion that 2-Br-4,5-MDMA should not be expected to be an MDMA-like substrate of SERT, indicating that aromatic bromination at C(2) modulates the pharmacodynamic properties of the substrate MDMA, yielding a citalopram-like compound.

Vortioxetine: a novel antidepressant for the treatment of major depressive disorder

ABSTRACTIntroduction: Vortioxetine is a novel antidepressant drug approved for the treatment of major depressive disorder (MDD) in adults. It is formulated into tablets and has a dose range of 5–20 mg. The recommended starting dose is 10 mg administered orally once daily without the need for food.Areas covered: This review focuses on the preclinical and clinical discovery of vortioxetine. It analyzes the pharmacological, neurochemical, and behavioral mechanisms of the medication and how these contribute to its potential therapeutic advantages as described in published preclinical and clinical studies and product labels.Expert opinion: Vortioxetine displays high affinity for serotonin transporter (SERT), and serotonin 5-HT3, 5HT1A, 5HT7 receptors. Functional studies show that vortioxetine acts as a SERT blocker, a 5-HT3, 5-HT7 receptor antagonist, and a 5-HT1A receptor agonist. The drug is active in animal models predictive of antipsychotic and antidepressant activities and demonstrates procognitive effects in several animal models that assessed memory, cognition, and executive functions. Short- and long-term clinical trials demonstrated the clinical efficacy of vortioxetine in treating depressive symptoms and cognitive deficits in MDD patients. It also displays fairly benign safety and tolerability profiles. Vortioxetine’s unique psychopharmacological properties might contribute to an improved clinical outcome in MDD patient populations.

Computation-guided analysis of paroxetine binding to hSERT reveals functionally important structural elements and dynamics

The serotonin transporter (SERT) is one of the primary targets for medications to treat neuropsychiatric disorders and functions by exploiting pre-existing ion gradients of Na+, Cl−, and K+ to translocate serotonin from the synaptic cleft into the presynaptic neuron. Although recent hSERT crystal structures represent a milestone for structure-function analyses of mammalian neurotransmitter:sodium symporters, they are all derived from thermostabilized but transport-deficient constructs. Two of these structures are in complex with paroxetine, the most potent selective serotonin reuptake inhibitor known. In this study, by carrying out and analyzing the results of extensive and comparative molecular dynamics simulations while also re-evaluating the transport and binding properties of the thermostabilized constructs, we identified functionally important structural elements that are perturbed by these mutations, revealed unexpected dynamics in the central primary binding site of SERT, and uncovered a conceivable ambiguity in paroxetine's binding orientation. We propose that the favored entropy contribution plays a significant role in paroxetine's extraordinarily high affinity for SERT. Our findings lay the foundation for future mechanistic studies and rational design of high-affinity SERT inhibitors.This article is part of the issue entitled ‘Special Issue on Neurotransmitter Transporters’.

Role of Serotonin Transporter in Antidepressant-Induced Diabetes Mellitus: A Pharmacoepidemiological-Pharmacodynamic Study in VigiBase®.

The association between antidepressant exposure and type 2 diabetes mellitus is still debated. Moreover, the pharmacological mechanisms remain unknown. The objective of this study was to investigate this putative relationship with the role of antidepressant pharmacological targets using the 'pharmacoepidemiological-pharmacodynamic' method. First, we performed case/non-case analyses in VigiBase® (the World Health Organization international database of suspected adverse drug reactions) to examine a signal of increased type 2 diabetes reporting (expressed as the reporting odds ratio and its 95% confidence interval) for antidepressants in general; examine and rank type 2 diabetes signals between the different pharmacological classes of antidepressants and the different antidepressants (58 in total). Second, we performed linear regression analyses to explore the association between the type 2 diabetes signal ranked between antidepressants and their binding affinities for nine targets (serotonin, norepinephrine, dopamine transporters, 5-HT2C serotonin, D2 dopamine, α1, α2 adrenergic, M3 muscarinic and H1 histamine receptors). A significant type 2 diabetes signal was found for antidepressants in general, three classes of antidepressants (tricyclic antidepressants, serotonin reuptake inhibitors and "other" antidepressants) and 15 individual antidepressants in particular. Among the antidepressants, three serotonin reuptake inhibitors [escitalopram (adjusted reporting odds ratio 1.15 [1.07-1.25]), paroxetine (1.15 [1.07-1.23]), sertraline (1.23 [1.17-1.31])] and three "other" antidepressants [duloxetine (1.15 [1.07-1.23]), trazodone (1.20 [1.09-1.32]), venlafaxine (1.15 [1.08-1.23])] were the antidepressants most frequently reported with type 2 diabetes. We found a significant correlation between the type 2 diabetes signal and serotonin transporter affinity (slope = 0.14 [0.06-0.23], p = 0.003, R2 = 0.43) but not the other targets. The present study suggests a potential role for serotonin transporter in antidepressant-induced type 2 diabetes.

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT1A activity. Part 5

A series of novel 4-aryl-pyrido[1,2-c]pyrimidine derivatives containing a 1-(2-quinoline)piperazine moiety was synthesized. The chemical structure of new compounds was confirmed by FT-IR, 1H NMR, 13C NMR and HRMS spectra as well as elemental analysis. Affinity of the novel pyrido[1,2-c]pyrimidine derivatives for 5-HT1A, 5-HT2A receptors and serotonin transporter (SERT) was evaluated in an in vitro radioligand binding assay. Tested compounds showed moderate to high affinity for 5-HT1AR and SERT and low affinity for 5-HT2AR. Selected ligands were subjected to in vivo tests, such as induced hypothermia and the forced swimming test in mice, which determined presynaptic agonistic activity of the ligands 8d, 8e, 9d and 9e and presynaptic antagonistic activity of the ligands 8a, 8b, 9a, 9b. Additionally, metabolic stability evaluation was performed for selected ligands, proving that a para-substitution in the 4-aryl-pyrido[1,2-c]pyrimidine moiety leads to an increase in stability, whereas a substitution in the ortho-position lowers the stability.

The antidepressant-like pharmacological profile of Yuanzhi-1, a novel serotonin, norepinephrine and dopamine reuptake inhibitor

Triple reuptake inhibitors that block dopamine transporters (DATs), norepinephrine transporters (NETs), and serotonin transporters (SERTs) are being developed as a new class of antidepressants that might have better efficacy and fewer side effects than traditional antidepressants. In this study, we performed in vitro binding and uptake assays as well as in vivo behavioural tests to assess the pharmacological properties and antidepressant-like efficacy of Yuanzhi-1. In vitro, Yuanzhi-1 had a high affinity for SERTs, NETs, and DATs prepared from rat brain tissue (Ki=3.95, 4.52 and 0.87nM, respectively) and recombinant cells (Ki=2.87, 6.86 and 1.03nM, respectively). Moreover, Yuanzhi-1 potently inhibited the uptake of serotonin (5-hydroxytryptamine; 5-HT), norepinephrine (NE) and dopamine (DA) into rat brain synaptosomes (Ki=2.12, 4.85 and 1.08nM, respectively) and recombinant cells (Ki=1.65, 5.32 and 0.68nM, respectively). In vivo, Yuanzhi-1 decreased immobility in a dose-dependent manner, which was shown among rats via the forced-swim test (FST) and mice via the tail-suspension test (TST). The results observed in the behavioural tests did not appear to result from the stimulation of locomotor activity. Repeated Yuanzhi-1 treatment (2.5, 5 or 10mg/kg) significantly reversed depression-like behaviours in chronically stressed rats, including reduced sucrose preference, decreased locomotor activity, and prolonged time to begin eating. Furthermore, in vivo microdialysis studies showed that 5- and 10-mg/kg administrations of Yuanzhi-1 significantly increased the extracellular concentrations of 5-HT, NE and DA in the frontal cortices of freely moving rats. Therefore, Yuanzhi-1 might represent a novel triple reuptake inhibitor and possess antidepressant-like activity.

A Molecular Dynamics Study on SSRI Antidepressant Drugs

Selective serotonin reuptake inhibitors (SSRIs) are a rationally designed class of antidepressants which act via inhibition of the serotonin transporter (SERT), resulting in increased serotonin concentrations in the synaptic cleft. This group of drugs is thought to be selective for SERT rather than norepinephrine and dopamine transporters (respectively NET and DAT).We used a computational approach to determine the drugs with the highest affinity and selectivity for SERT. We used molecular docking, energy minimization, molecular dynamics simulations and umbrella sampling to estimate the Gibbs binding free energy for each protein-drug complex.Our results qualitatively agree with corresponding experimental data. Among the SSRIs we studied, paroxetine has the highest affinity for SERT and NET, and sertraline for DAT. Our results confirmed the selectivity of this class of drugs for SERT rather than NET and DAT. We found citalopram was the most selective drug for SERT in this class.These results can be used for future studies on designing SSRIs with higher affinity and selectivity.