Allosteric Binding of MDMA to the Human Serotonin Transporter (hSERT) via Ensemble Binding Space Analysis with ΔG Calculations, Induced Fit Docking and Monte Carlo Simulations.

Despite the recent promising results of MDMA (3,4-methylenedioxy-methamphetamine) as a psychotherapeutic agent and its history of misuse, little is known about its molecular mode of action. MDMA enhances monoaminergic neurotransmission in the brain and its valuable psychoactive effects are associated to a dual action on the 5-HT transporter (SERT). This drug inhibits the reuptake of 5-HT (serotonin) and reverses its flow, acting as a substrate for the SERT, which possesses a central binding site (S1) for antidepressants as well as an allosteric (S2) one. Previously, we characterized the spatial binding requirements for MDMA at S1. Here, we propose a structure-based mechanistic model of MDMA occupation and translocation across both binding sites, applying ensemble binding space analyses, electrostatic complementarity, and Monte Carlo energy perturbation theory. Computed results were correlated with experimental data (r = 0.93 and 0.86 for S1 and S2, respectively). Simulations on all hSERT available structures with Gibbs free energy estimations (ΔG) revealed a favourable and pervasive dual binding mode for MDMA at S2, i.e., adopting either a 5-HT or an escitalopram-like orientation. Intermediate ligand conformations were identified within the allosteric site and between the two sites, outlining an internalization pathway for MDMA. Among the strongest and more frequent interactions were salt bridges with Glu494 and Asp328, a H-bond with Thr497, a π-π with Phe556, and a cation-π with Arg104. Similitudes and differences with the allosteric binding of 5-HT and antidepressants suggest that MDMA may have a distinctive chemotype. Thus, our models may provide a framework for future virtual screening studies and pharmaceutical design and to develop hSERT allosteric compounds with a unique psychoactive MDMA-like profile.

Garlic passion fruit (Passiflora tenuifila Killip): Assessment of eventual acute toxicity, anxiolytic, sedative, and anticonvulsant effects using in vivo assays.

Several Passiflora species are known for their sedative and anxiolytic properties. However, the functional properties of Passiflora tenuifila Killip are still unexplored. The objective of this work was to evaluate the phenolic composition and acute toxicity, anxiolytic, sedative, and anticonvulsant effects using in vivo assays. The whole fruit (peel, pulp, and seed) was lyophilized and used for all assays. LC-MS showed 19 phenolic compounds, tentatively identified as flavonoids and phenolic acids. Acute treatment with single doses of up to 2000 mg kg-1 in Wistar rats showed no signs of mortality or toxicity over 14 days. The assay of functional effects was performed with Swiss mice, four groups, received by gavage, doses of P. tenuifila (200 or 400 mg kg-1 body weight), water, and diazepam (as negative and positive control), and behavior tests were performed after 60 min of the treatments. The animals treated with P. tenuifila fruit showed a significant decrease in locomotor activity, indicating a sedative and anxiolytic activity. No significant changes were observed in the rotarod apparatus, suggesting that the P. tenuifila fruit did not cause muscle relaxation. The 400 mg kg-1 dose of P. tenuifila exerted a protective effect against pentylenetetrazole-induced seizures, decreasing the severity and not causing the death of the animals. In conclusion, P. tenuifila showed no acute toxicity and had a promising effect as an anxiolytic agent, hypnotic-sedative and anticonvulsant, which could be related to its composition of flavonoids and phenolic acids.

Electrophysiology and Behavioral Assessment of the New Molecule SMe1EC2M3 as a Representative of the Future Class of Triple Reuptake Inhibitors.

SMe1EC2M3 is a pyridoindole derivative related to the neuroleptic drug carbidine. Based on the structural similarities of SMe1EC2M3 and known serotonin (5-HT), norepinephrine, and dopamine reuptake inhibitors, we hypothesized that this compound may also have triple reuptake inhibition efficacy and an antidepressant-like effect. PreADMET and Dragon software was used for in silico prediction of pharmacokinetics and pharmacodynamics of SMe1EC2M3. Forced swim test was used to evaluate its antidepressant-like effects. Extracellular in vivo electrophysiology was used to assess 5-HT, norepinephrine, and dopamine reuptake inhibition efficacy of SMe1EC2M3. PreADMET predicted reasonable intestinal absorption, plasma protein binding, and blood-brain permeability for SMe1EC2M3. Dragon forecasted its efficiency as an antidepressant. Using behavioral measurements, it was found that SMe1EC2M3 decreased immobility time and increase swimming time during the forced swim test (FST). Electrophysiological investigations showed that SMe1EC2M3 dose-dependently suppressed the excitability of 5-HT neurons of the dorsal raphe nucleus (DRN), norepinephrine neurons of the locus coeruleus (LC), and dopamine neurons of the ventral tegmental area (VTA). The SMe1EC2M3-induced suppression of 5-HT, norepinephrine, and dopamine neurons was reversed by the antagonists of serotonin-1A (5-HT1A; WAY100135), α-2 adrenergic (α2, yohimbine), and dopamine-2 receptors (D2, haloperidol), respectively. We conclude that SMe1EC2M3 is prospective triple 5-HT, norepinephrine, and dopamine reuptake inhibitor with antidepressant-like properties, however future studies should be performed to complete the pharmacological profiling of this compound.

In-vitro and in situ assessment of the efflux of five antidepressants by breast cancer resistance protein.

OBJECTIVES: Antidepressants need to penetrate the blood-brain barrier (BBB) to exert their functions in the central nervous system. Breast cancer resistance protein (BCRP), an efflux transporter abundantly expressed in the BBB, prevents the accumulation of many drugs in the brain. This study aimed to identify whether five commonly used antidepressants (sertraline, duloxetine, fluoxetine, amitriptyline and mirtazapine) are BCRP substrates. METHODS: A combination of bidirectional transport and intracellular accumulation experiments was conducted on BCRP-overexpressing MDCKII and wild-type (WT) cells, and in situ brain perfusion was conducted in rats. KEY FINDINGS: The bidirectional transport study revealed that the net efflux ratio (NER) of sertraline reached 2.08 but decreased to 1.06 when co-incubated with Ko143, a selective BCRP inhibitor. Conversely, the other four antidepressants did not appear to be BCRP substrates, due to their low NER values (<1.5). The accumulation of sertraline in MDCKII-BCRP cells was significantly lower than that in MDCKII-WT cells. The presence of Ko143 significantly increased the sertraline accumulation in MDCKII-BCRP cells but not in MDCKII-WT cells. Brain perfusion showed that the permeability of 1 and 5 µm sertraline was significantly higher in the presence of Ko143. CONCLUSIONS: Taken together, BCRP is involved in sertraline efflux.

Assessment of Antidepressant Effect of the Aerial Parts of Micromeria myrtifolia Boiss. & Hohen on Mice.

The currently available antidepressant agents necessitate the development of newer alternatives because of their serious adverse effects and costs. Traditional medicinal knowledge is likely the key that opens the door to discover new medicines. In Turkish folk medicine, the infusion prepared from aerial parts of Micromeria myrtifolia Boiss. & Hohen is used as pleasure and medicinal tea for its relaxing action. The present research was conceived to confirm the antidepressant's potential of this traditional medicinal plant. In this process, first of all, the collected and shade-dried aerial parts of M. myrtifolia were powdered and then, extracted using solvents with different polarity as follows; n-hexane, ethyl acetate (EtOAc), and methanol (MeOH). The antidepressant activity of the extracts was evaluated by using several in vivo and in vitro experimental models of depression. When the data obtained from the control and experimental groups were compared, it was determined that the MeOH extract was the most active. The active components of this extract were isolated and identified utilizing various chromatographic separation techniques. The MeOH extract was applied to reversed phase (RP-18) column chromatography to obtain five main fractions and they were tested on antidepressant activity models. The isolated compounds from the obtained fractions were elucidated as rosmarinic acid (1), myricetin (2), apigenin (3), and naringenin (4) which were assumed to be responsible for the antidepressant activity of the aerial parts. According to the results, rosmarinic acid, myricetin, apigenin, and naringenin showed statistically significant activity on forced swimming test and tetrabenazine-induced ptosis models, whereas only rosmarinic acid showed statistically significant activity on the tail suspension test. Apigenin displayed the highest inhibitory activity on MAO A and B enzymes. Studies in the future should be performed to investigate the antidepressant activity mechanism of these natural compounds. The current research could be an important step in the development of the new agents that can be used in the treatment of depression.

Ketamine metabolites with antidepressant effects: Fast, economical, and eco-friendly enantioselective separation based on supercritical-fluid chromatography (SFC) and single quadrupole MS detection.

Increasing evidence accumulates that metabolites of the dissociative anesthetic ketamine contribute considerably to the biological effects of this drug and could be developed as next generation antidepressants, especially for acute treatment of patients with therapy-refractory major depression. Analytical methods for the simultaneous determination of the plethora of hydroxylated, dehydrogenated and/or demethylated compounds formed after administration of ketamine hydrochloride are a prerequisite for future clinical investigations and a deeper understanding of the individual role of the isomers of these metabolites. In this study, we present development and validation of a method based on supercritical-fluid chromatography (SFC) coupled to single quadrupole MS detection that allows the separation of ketamine as well as all of its relevant metabolites detected in urine of healthy volunteers. Inherently to SFC methods, the run times of the novel protocol are four times shorter than in a comparable HPLC method, the use of organic solvents is reduced and we were able to demonstrate and validate the successful enantioselective separation and quantification of R- and S-ketamine, R- and S-norketamine, R- and S-dehydronorketamine and (2R,6R)- and (2S,6S)-hydroxynorketamine isomers differing in either constitution, stereochemistry, or both, in one run. The developed method may be useful in investigating the antidepressant efficacy of ketamine in clinical trials.

Lithium adduct as precursor ion for sensitive and rapid quantification of 20 (S)-protopanaxadiol in rat plasma by liquid chromatography/quadrupole linear ion trap mass spectrometry and application to rat pharmacokinetic study.

A novel, rapid and sensitive liquid chromatography/quadrupole linear ion trap mass spectrometry [LC-ESI-(QqLIT)MS/MS] method was developed and validated for the quantification of protopanaxadiol (PPD) in rat plasma. Oleanolic acid (OA) was used as internal standard (IS). A simple protein precipitation based on acetonitrile (ACN) was employed. Chromatographic separation was performed on a Sepax GP-C18 column (50 × 2.1 mm, 5 µM) with a mobile phase consisting of ACN-water and 1.5 µM formic acid and 25 mM lithium acetate (90 : 10, v/v) at a flow rate of 0.4 ml/min for 3.0 min. Multiple-reaction-monitoring mode was performed using lithium adduct ion as precursor ion of m/z 467.5/449.4 and 455.6/407.4 for the drug and IS, respectively. Calibration curve was recovered over a concentration range of 0.5-100 ng/ml with a correlation coefficient >0.99. The limit of detection was 0.2 ng/ml in rat plasma for PPD. The results of the intraday and interday precision and accuracy studies were well within the acceptable limits. The validated method was successfully applied to investigate the pharmacokinetic study of PPD after intravenous and gavage administration to rat.

SMILES-based QSAR model for arylpiperazines as high-affinity 5-HT(1A) receptor ligands using CORAL.

A predictive quantitative structure - activity relationships model of arylpiperazines as high-affinity 5-HT(1A) receptor ligands was developed using CORAL software (http://www.insilico.eu/CORAL). Simplified molecular input-line entry system (SMILES) was used as representation of the molecular structure of the arylpiperazines. The balance of correlations was used in the Monte Carlo optimization aimed to build up optimal descriptors for one-variable models. The robustness of this model has been tested in four random splits into the sub-training, calibration, and test set. The obtained results reveal good predictive potential of the applied approach: correlation coefficients (r²) for the test sets of the four random splits are 0.9459, 0.9249, 0.9473 and 0.9362.

Strategy for a genetic assessment of antipsychotic and antidepressant-related proarrhythmia.

Antidepressants and antipsychotics may affect several ion channels involved in the control of cardiac action potential and be proarrhythmic. In this field, accurate understanding of genetics, which per se is a non-controllable risk factor, may help clinicians to prevent life-threatening side effects. So far, a number of genes have been associated with arrhythmia: SCN5A, SCN4B, CACNL1AC, KCNH2, KCNQ1, KCNE1, ANK2, ALG10, KCNJ2, KCNE2, RYR2, KCND3, KCND2, ACE, NOS1AP, CASQ2 and Rad. These genes represent good candidates for the definition of a genetic pro-arrhythmic profile. A genetic analysis of these targets is provided and their possible pathophysiological role in arrhythmias is discussed. Special attention is devoted to the interactions between these genes and new generation antidepressants and antipsychotics. A list of relevant rare mutations within the selected genes is presented, together with a complete list of Tag SNPs covering the whole genetic sequence. The aim of this paper is to define a part of the genetic framework responsible for the proarrhythmic effects of antidepressants and antipsychotics. The selected variants, both mutations and polymorphisms, may help in defining a next-to-come genetic assessment to be performed before drug prescription in order to improve drug safety.

Enantioseparation of the antidepressant reboxetine.

The enantioseparation of reboxetine by HPLC was investigated using chiral stationary phases (CSPs) containing cellulose Tris(3,5-dimethylphenyl)carbamate on silica gel (Chiralcel OD column) as the chiral selector. Reversed phase HPLC was the technique of choice for the analytical enantioseparation of reboxetine, while the chiral semipreparative separation was obtained with the same CSP, but in normal phase conditions. The effects of the mobile phase pH and composition on analytical retention, enantioselectivity and resolution were investigated. The best performance was obtained using a mobile phase composed of 0.5M sodium perchlorate at pH 6 and acetonitrile in the 60/40 (v/v) ratio. The semipreparative separation has allowed obtaining pure enantiomers, but required the preparation of reboxetine free base. Different n-hexane/alcohol mixtures were tested as mobile phases, varying both the nature of the alcohol and its percentage in the mobile phase. Different n-hexane/alcohol mixtures were tested as mobile phase and the best results were obtained by using a mobile phase composed of n-hexane and 2-propanol (80:20, v/v).

Vasopressin antagonists as anxiolytics and antidepressants: recent developments.

A compelling case for the potential utility of vasopressin (AVP) antagonists as a novel therapeutic class for the treatment of stress-related affective illness has emerged based on observations in depressed individuals, findings in animal models of anxiety and depression, and an understanding of changes in hypothalamic-pituitary-adrenal (HPA) axis regulation under chronic stress. The scientific bases for vasopressin antagonists as a pharmacotherapy for anxiety and depression include: 1) the neuroadaptation and dysregulation of HPA function that accompanies chronic stress in affected humans and in animal models of anxiety and depression, 2) recognition that AVP, not corticotrophin releasing factor (CRF), drives HPA function associated with chronic psychological stress, 3) the CNS localization of vasopressin V1a and V1b receptors in limbic system regions involved in HPA regulation and control of social behaviors, and 4) preclinical data showing efficacy in animal models employed as screens for anxiolytic and antidepressant activity. The public health need for new pharmaceutical treatments for stress-related affective illness is well documented. In the United States alone, anxiety and depression affect some 40 million people each year and carry a conservatively estimated annual total economic burden of at least $125 billion. Existing pharmacotherapies for both indications are not uniformly effective and frequently have undesirable side effects. These limitations demonstrate that a new treatment approach through vasopressin receptor antagonism in the CNS may offer significant opportunities for improved outcomes. In this review, the development of compounds in this class since 2005 is considered. The most advanced clinical candidates and newer compounds described in recent patents are presented.

High prevalence of orthostatic hypotension and its correlation with potentially causative medications among elderly veterans.

BACKGROUND: Orthostatic hypotension (OH) is defined as a reduction of systolic blood pressure of at least 20 mmHg, or diastolic blood pressure of at least 10 mmHg from a sitting to a standing position. It is a common physical finding among older adults and associated with significant morbidity and mortality. Use of medications that have the potential to induce OH, particularly concomitant use of several of such medications, is a major factor for the development of OH. OBJECTIVES: To describe the prevalence of symptomatic and asymptomatic OH in veterans aged 75 years and older attending a geriatric clinic, and to assess the association between OH and the number of potentially causative medications used. METHODS: Charts of all patients who attended a VA geriatric clinic (Michael E. DeBakey VA Medical Center) during the period of 1 June 2002 to 1 June 2003 were reviewed retrospectively for (i) the use of potentially causative medications, i.e. medications that were reported to cause OH in at least 1% of the general population and that were available in the VA formulary, (ii) the presence or absence of OH, and (iii) the presence or absence of symptomatic OH. Patients with primary autonomic dysfunction, Parkinson's disease, and patients who were unable to stand, or who had no assessment for both sitting and standing blood pressure for other reasons were excluded. RESULTS: A total of 505 individual patients attended the clinic during the study period, and 342 patients fit the inclusion criteria. About 189 of these patients (55%) had OH. Among patients with OH, 61 patients (33%) were symptomatic, including 52 patients who had falls. The prevalence of OH in patients receiving zero, one, two, and three or more potentially causative medications was 35, 58, 60 and 65% respectively. Receiving hydrochlorothiazide was associated with the highest prevalence of OH (65%), followed by receiving lisinopril (60%), trazodone (58%), furosemide (56%) and terazosin (54%). CONCLUSION: The prevalence of OH is very high in older veterans and significantly related to the number of concurrent causative medications used. Providers should be educated to reduce the amount of potentially causative medications in the elderly and better assess patients in which use of such medications is necessary to avoid symptomatic OH.

Choosing appropriate antidepressant therapy in the elderly. A risk-benefit assessment of available agents.

This article discusses the advantages and disadvantages of tricyclic antidepressants (TCAs), tetracyclic antidepressants (i.e. mianserin), selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs), triazolopyridines (i.e. trazodone), phenylpiperazines (i.e. nefazodone), serotonin and noradrenaline (norepinephrine) reuptake inhibitors (i.e. venlafaxine), and aminoketones [i.e. amfebutamone (bupropion)] in the treatment of late-life depression. A limitation of the existing literature is that most data regarding drugs are derived from studies that have involved medically stable outpatients who do not have dementia and who are less than 80 years of age. There is a paucity of data on the use of antidepressants in very elderly individuals, patients who have significant medical comorbity and patients with dementia or other neurological problems. No one class of antidepressant has been found to be more effective than another in the acute treatment of geriatric major depression. However, given design short-comings in many of these studies, the possibility of a real difference in efficacy between drugs (especially in the treatment of severe or melancholic depression) cannot be excluded. With respect to adverse effects, drug interactions, and dosage and administration, each class of antidepressant has its benefits and limitations. There is no one 'first-line' antidepressant for elderly patients with depression. Selection of an antidepressant should be made on a case by case basis, taking into account each patient's characteristics.

Synthesis, toxicological, and pharmacological assessment of derivatives of 2-aryl-4-(3-arylpropyl)morpholines.

The synthesis of nine original morpholine derivatives, i.e. 2-aryl-4-(3-arylpropyl)morpholines, is described. The structure of all synthesised derivatives was proved by IR and 1H-NMR, and some of them by 13C-NMR. Acute toxicity studies of the compounds were performed on mice. A comparative pharmacological study of the in vivo effects on the central nervous system was undertaken using the screening tests: hexobarbital induced sleeping time: locomotor activity; and behaviour despair (for antidepressive activity). The most active compound 4-(2-benzoylethyl)-2-phenyl-3-methyl) morpholine 4e was studied for MAO-A and MAO-B inhibition in vitro in rat brain mitochondria preparations.