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Modeling K(m) values using electrotopological state: substrates for cytochrome P450 3A4-mediated metabolism.

In order to determine K(m) values of substrates for CYP3A4-mediated metabolism, an in silico model has been developed in the present work. Using electrotopological state (E-state) indices, together with Bayesian-regularized neural network (BRNN), we have described an in silico method to model log(1/K(m)) values of various substrates. The relative importance of the E-state indices is analyzed by principal component analysis. By using an additional external test set, which is independent of the training set, the robustness and predictivity of the model are also validated.

Computational Biology↗

Blockade of supraspinal 5-HT1A receptors potentiates the inhibitory effect of venlafaxine on wind-up activity in mononeuropathic rats.

In mononeuropathic rats submitted to a C-fiber reflex responses paradigm, repeated administration (five successive injections every half-life) of 10 mg/kg, s.c. of venlafaxine, but not of 2.5 mg/kg, s.c., a mixed monoamine reuptake inhibitor with preferential inhibitory activity in 5-HT reuptake, induced a progressive reduction of spinal wind-up. Repeated co-administration of the selective 5-HT1A receptor antagonist WAY 100,635 i.c.v. (50 microg/injection) significantly increased the effect of venlafaxine s.c., indicating that venlafaxine-induced inhibition of spinal wind-up in mononeuropathic rats is potentiated by blockade of central 5-HT1A receptors.

Animals↗

Cannabinoid system in the budgerigar brain.

Cannabinoid receptor density and cannabinoid receptor-mediated G protein stimulation were studied by autoradiographic techniques throughout the budgerigar (Melopsittacus undulatus) brain. The maximal CB(1) receptor density value (using [(3)H]CP55,940 as radioligand) was found in the molecular layer of the cerebellum (Mol), and high binding values were observed in the nucleus taeniae amygdalae (TnA), nucleus preopticus medialis, and nucleus pretectalis. The highest net-stimulated [(35)S]GTPgammaS binding values induced by the selective CB(1) receptor agonist WIN55,212-2 were observed in the nucleus paramedianus internus thalami, and high values of [(35)S]GTPgammaS binding were observed in the TnA, Mol, arcopallium dorsale and arcopallium intermedium. The distribution data suggest that in the budgerigar, as previously indicated in mammals, cannabinoid receptors may be related to the control of several brain functions in the motor system, memory, visual system, and reproductive behavior. The discrepancies between the cannabinoid receptor densities and the cannabinoid receptor-mediated stimulation found in several budgerigar brain nuclei support the hypothesis, previously described for mammals, of the existence of different G(i/o) protein populations able to associate with the cannabinoid receptors, depending on the brain structure, and could reflect the relative importance that cannabinoid transmission could exerts in each cerebral area.

Animals↗

Pharmacokinetic and pharmacodynamic profiles of the novel serotonin and norepinephrine reuptake inhibitor desvenlafaxine succinate in ovariectomized Sprague-Dawley rats.

Desvenlafaxine succinate (DVS) is a novel serotonin (5-HT) and norepinephrine (NE) reuptake inhibitor (SNRI) that is currently in clinical development for the treatment of major depressive disorder and vasomotor symptoms associated with menopause. Previous studies have documented the pharmacokinetic and pharmacodynamic profiles of DVS in male rats. Similar studies, however, have not been performed in ovariectomized (OVX) rats, a model that mimics the loss of ovarian hormones that occurs at menopause. The goal of the present study, therefore, was to characterize the pharmacokinetic and pharmacodynamic properties of DVS in OVX rats. Desvenlafaxine levels peaked in plasma, brain (total brain minus hypothalamus) and hypothalamus at concentrations of 7.0, 10.8 and 9.5 microM (assuming 1 g = 1 ml), respectively, 30 min post-dosing DVS (30 mg/kg, oral). The apparent terminal half-lives of desvenlafaxine in plasma, brain and hypothalamus were 3.0, 2.1 and 2.5 h, respectively. Based on AUC(0-last), brain to plasma and hypothalamus to plasma ratios were 1.7 and 1.3, respectively. Microdialysis experiments in the medial preoptic area of the hypothalamus showed that DVS (30 mg/kg, s.c.), in the presence of WAY-100635 (5-HT(1A) antagonist), increased 5-HT levels 225% at 1 h post-dosing. Norepinephrine levels increased 44% at 3 h post-dosing while dopamine levels were unchanged. Thus, in OVX rats, DVS has good pharmacokinetic properties, rapid brain penetration, excellent brain penetrability and selectively increases 5-HT and NE levels in the hypothalamus. This work supports the notion that DVS could have utility for treating disorders in menopausal women in which changes in 5-HT and/or NE have been implicated.

Adrenergic Uptake Inhibitors↗

A cannabinoid receptor 1 mutation proximal to the DRY motif results in constitutive activity and reveals intramolecular interactions involved in receptor activation.

Activation of a G-protein-coupled receptor involves changes in specific microdomain interactions within the transmembrane region of the receptor. Here, we have focused on the role of L207, proximal to the DRY motif of the human cannabinoid receptor 1 in the interconversion of the receptor resting and active states. Ligand binding analysis of the mutant receptor L207A revealed an enhanced affinity for agonists (three- to six-fold) and a diminished affinity for inverse agonists (19- to 35-fold) compared to the wild-type receptor, properties characteristic of constitutive activity. To further examine whether this mutant adopts a ligand-independent, active form, treatment with GTPgammaS was used to inhibit G protein coupling. Under these conditions, the L207A receptor exhibited a 10-fold increase in affinity for the inverse agonist SR141716A, consistent with a shift away from an enhanced precoupled state. Analysis of the cellular activity of the L207A receptor showed elevated basal cyclic AMP accumulation relative to the wild type that is inhibited by SR141716A, consistent with receptor-mediated Gs precoupling. Using toxins to selectively abrogate Gs or Gi coupling, we found that CP55940 nonetheless induced only a Gi response suggesting a strong preference of this ligand-bound form for Gi in this system. Molecular dynamics simulations reveal that the single residue change of L207A impacts the association of TM3 and TM6 in the receptor by altering hydrophobic interactions involving L207, the salt bridge involving the Arg of the DRY motif, and the helical structure of TM6, consistent with events leading to activation. The structural alterations parallel those observed in models of a mutant CB(1) receptor T210I, with established constitutive activity (D'Antona, A.M., Ahn, K.H. and Kendall, D.A., 2006. Mutations of CB1 T210 produce active and inactive receptor forms: correlations with ligand affinity, receptor stability, and cellular localization. Biochemistry, 45, 5606-5617).

Amino Acid Motifs↗

Synthesis of (+)-(2R,3S,4R)-2,3,4-trihydroxycyclohexanone from D-glucose.

We have described the synthesis of (+)-(2R,3S,4R)-2,3,4-trihydroxycyclohexanone by the reduction of a keto-conduritol derivative, the latter being prepared in five steps from (-)-(2S,3R,4S,5S)-2,3,4-tribenzyloxy-5-hydroxycyclohexanone, which is in turn readily synthesized from D-glucose.

Cyclohexanols↗

Preparation and evaluation of a chiral stationary phase covalently bound with chiral pseudo-1 8-crown-6 ether having 1-phenyl-1,2-cyclohexanediol as a chiral unit.

A chiral stationary phase (CSP) has been prepared by chemically bonding a chiral pseudo-18-crown-6 type host having a 1-phenyl-1,2-cyclohexanediol unit to 3-aminopropyl silica gel. The chiral column was prepared by the slurry-packing method in a stainless steel HPLC column. Normal mobile phases can be used with this CSP in contrast to conventional dynamic coating type CSPs. Enantiomers of 20 out of 30 amino compounds, including 20 amino acids, 2 amino acid methyl esters, 6 amino alcohols, and 2 lipophilic amines, were efficiently separated on columns with this CSP. It is noteworthy that 15 amino compounds out of 30 were separated with better separation factors and shorter retention times compared to the corresponding CSP having pseudo-18-crown-6 with 1-phenyl-1,2-ethanediol as a chiral unit. In view of the correlation between the enantiomer selectivities observed in chromatography and those obtained in gas phase FABMS-EL methods and solution phase titrations, chiral recognition in the host-guest interaction likely contributes to enantiomer separation.

Amino Acids↗

Design and evaluation of a coupled monolithic pre-concentrator-capillary zone electrophoresis system for the extraction of immunoglobulin G from human serum.

The analysis of proteins in biological fluids by capillary electrophoresis (CE) is of interest in clinical chemistry. However, due to low analyte concentrations and poor concentration limits of detection (CLOD), protein analysis by this technique is frequently challenging. Coupling preconcentration techniques with CE greatly improves the CLOD. An on-line preconcentration-CE method that can selectively pre-concentrate any protein for which an antibody is available would be very useful for the analysis of low abundance proteins and would establish CE as a major tool in biomarker discovery. To accomplish this, the development of an on-line protein G monolithic pre-concentrator-CE device is proposed. To generate active groups for protein immobilization, glycidyl methacrylate (GMA) was used to prepare polymer monoliths. A 1.5-2 cm monolith was cast inside a 75 microm I.D. fused silica capillary that had previously been coated with alternating layers of negatively (dextran) and positively (polybrene) charged polymers. Protein G was covalently bound to GMA. Monoliths from different formulations were prepared and evaluated for binding capacity to optimize the monolith formulation for protein preconcentration. The physical properties of the column considered best for preconcentration were determined by mercury intrusion porosimetry. The total pore area was 4.8m(2)/g, the average pore diameter was 3.3 microm and the porosity was 82%. The monolith had a low flow resistance and was macroscopically homogeneous. The effectiveness of the monolith to rapidly pre-concentrate proteins at flow rates as high as 10 microL/min was demonstrated using a 1.8 microM IgG solution. This system proved effective for on-line sample extraction, clean-up, preconcentration, and CE of IgG in human serum. IgG from diluted (500 and 65,000 times) human serum samples was successfully analyzed using this system. The approach can be applied to the on-line preconcentration and analysis of any protein for which an antibody is available.

Adsorption↗

Development of a solid phase extraction for 13 'new' generation antidepressants and their active metabolites for gas chromatographic-mass spectrometric analysis.

A solid phase extraction procedure (SPE) for 13 'new' antidepressants (venlafaxine, fluoxetine, viloxazine, fluvoxamine, mianserin, mirtazapine, melitracen, reboxetine, citalopram, maprotiline, sertraline, paroxetine and trazodone) together with eight of their metabolites (O-desmethylvenlafaxine, norfluoxetine, desmethylmianserine, desmethylmirtazapine, desmethylcitalopram, didesmethylcitalopram, desmethylsertraline and m-chlorophenylpiperazine) from plasma is optimized using HPLC-DAD as monitoring system. Special attention has been paid to the choice of washing and eluting solvent, resulting in a highly concentrated, clean and moisture free extract, also suitable for GC-MS. A total number of 10 sorbents (apolar, polymeric, ion-exchange and mixed mode) was evaluated. Based on recovery, reproducibility and absence of interfering substances the strong cation exchanger gave the best results. Recoveries were determined at low and high therapeutic and toxic levels and ranged between 70 and 109% for all compounds, except for trazodone (39%).

Antidepressive Agents, Second-Generation↗

Venlafaxine versus amitriptyline in the prophylactic treatment of migraine: randomized, double-blind, crossover study.

In patients with migraine with or without aura the prophylactic effect of amitriptyline (AMT) and venlafaxine (VLF) was compared in a randomized double-blind crossover study. Intolerable side effects resulted in drop out of five patients on AMT (due to hypersomnia, difficulty in concentration and orthostatic hypotension) and one patient on VLF (because of nausea and vomiting). Following the run-in period the patients (n = 52) were randomly treated with one of the study medications for 12 weeks. After a wash-out period lasting 4 weeks the patients were treated with the other drug for further 12 weeks. Both drugs had significant beneficial effect on pain parameters. Total number of side effects of VLF was low when compared with the side effect profile of AMT. In conclusion, it is suggested that VLF may be considered for the prophylaxis of migraine because of its low and/or tolerable side effect properties.

Adolescent↗

A cost-effectiveness model of escitalopram, citalopram,and venlafaxine as first-line treatment for major depressive disorder in Belgium.

BACKGROUND: Economic evaluations aim to combine costs and patient outcomes in one analysis. OBJECTIVE: The purpose of this study was to assess the cost-effectiveness of escitalopram (vs all available competitors) for first-line treatment of major depressive disorder (MDD) in Belgium. METHODS: A 2-path decision analytic model with a 6-month horizon was used. All patients (baseline scores on the Montgomery-Asberg Depression Rating Scale [MADRS], > or =18 to < or =40) started at the primary path, and were referred to specialist care in the secondary care path. Model inputs included the following: probabilities from a meta-analysis of comparative trials data, an ad-hoc survey to evaluate pharmacologic treatment of depression in Belgium, literature, and a panel of experts. Main outcome measures were success (ie, remission [defined as MADRS < or =12]) and costs of treatment (ie, drug costs and medical care). Analyses were performed from the perspectives of the Belgian insurance system (IS) and society. The friction-cost method was used to estimate costs of lost productivity. Monetary values are reported in year-2003 Euros (1.0 approximately USD 1.1 in 2003). RESULTS: The expected success rate was 62.3% (95% CI, 60.1%-64.5%) for escitalopram compared with 57.2% (95% CI, 55.0%-59.4%) for citalopram. From the IS perspective, the expected cost per patient was Euros 390 (95% CI, Euros 372-Euros 409) for escitalopram compared with Euros 411 (95 % CI, Euros 391-Euros 431) for citalopram. From the societal perspective, these costs were Euros 1162 (95% CI, Euros 1106-Euros 1221) and Euros 1276 (95% CI, Euros 1216-Euros 1336), respectively. The success rates of venlafaxine (66.6% [95% CI, 64.2%-69.0%]) and escitalopram (67.0% [95% CI, 64.7%-69.4%]) were similar, but higher total costs were observed with venlafaxine, due to acquisition and secondary care costs. The use of data from various sources may have introduced bias. However, sensitivity analyses demonstrated that results of the model were robust. CONCLUSIONS: In this analysis, the treatment of MDD with escitalopram appeared to be a cost-effective alternative compared with citalopram and venlafaxine, leading to better clinical outcomes and cost savings compared with citalopram in the model used. The success rates were similar between venlafaxine and escitalopram, but higher total costs were observed with venlafaxine.

Antidepressive Agents, Second-Generation↗

Substance use disorder comorbidity in major depressive disorder: an exploratory analysis of the Sequenced Treatment Alternatives to Relieve Depression cohort.

Patients with major depressive disorder (MDD) often present with concurrent substance use disorders (SUD) involving alcohol and/or illicit drugs. This analysis compares the depressive symptomatic presentation and a range of clinical and demographic features of patients with MDD and concurrent SUD symptoms vs those without SUD symptoms, to clarify how these two differ and to determine whether concurrent SUD symptoms may alter the clinical presentation of MDD. The first 1500 outpatients with nonpsychotic MDD enrolled in the Sequenced Treatment Alternatives to Relieve Depression study were divided into those with and without concurrent SUD symptoms as ascertained by a self-report instrument, the Psychiatric Diagnostic Screening Questionnaire (PDSQ). Of the 1484 cases with completed baseline PDSQ, 28% (n = 419) of patients with MDD were found to endorse symptoms consistent with current SUD. Patients with symptoms consistent with SUD were more likely to be men (P < .0001), to be either divorced or never married (P = .018), to have a younger age of onset of depression (P = .014), and to have a higher rate of previous suicide attempts (P = .014) than those without SUD symptoms. Patients with major depressive disorder who have symptoms consistent with SUD endorsed greater functional impairment attributable to their illness than those without concurrent SUD symptoms (P = .0111). The presence of SUD symptoms did not alter the overall depressive symptom pattern of presentation, except that the dual-diagnosed patients had higher levels of hypersomnia (P = .006), anxious mood (P = .047), and suicidal ideation (P = .036) compared to those without SUD symptoms. In conclusion, gender, marital status, age of onset of major depression, functional impairment, and suicide risk factors differ in depressed patients with concurrent SUD symptoms compared to those without SUD comorbidity.

Adult↗

Structural-activity relationship study on C-4 carbon atom of the CB1 antagonist SR141716: synthesis and pharmacological evaluation of 1,2,4-triazole-3-carboxamides.

A series of 1,2,4-triazole-3-carboxamides has been prepared from alkyl-1,2,4-triazole-3-carboxylates under mild conditions. The ability of these triazoles to displace [3H]-CP55940 from CB1 cannabinoid receptor was measured. However, they showed only poor to moderate binding affinities, indicating that substitution of the C-4 pyrazole atom of the CB1 reference compound SR141716 by a nitrogen atom results in loss of affinity. Further investigations for functionality indicated that the compound 6a exhibited significant cannabinoid antagonistic properties in the mouse vas deferens functional assay. This leads us to the conclusion that 6a binds at a different CB1 binding site or at a new cannabinoid receptor subtype.

Animals↗

The effect of venlafaxine on ongoing and experimentally induced pain in neuropathic pain patients: a double blind, placebo controlled study.

BACKGROUND AND AIM: The aim of this randomized double blind placebo controlled study was to investigate the effectiveness and the safety of venlafaxine XR 75 and 150 mg on ongoing pain and on quantitative sensory tests in 60 patients with neuropathic pain for 8 weeks. METHODS: Evaluation parameters consisted of ongoing pain intensity (VAS), patient satisfaction, side effects, global efficacy and tolerance. Quantitative sensory measurements taken from the affected area before and after the drug treatment included pin-prick hyperalgesia, allodynia, detection and pain thresholds to electrical and heat stimuli, temporal summation of repetitive electrical and heat stimuli. RESULTS: A total of 55 patients completed the study. VAS scores decreased significantly compared to the baseline measurements in all groups. There was no significant difference between the groups regarding pain intensity and escape medication. The areas of allodynia and pin-prick hyperalgesia decreased significantly in venlafaxine groups compared to the placebo. There was no significant difference between the groups regarding the detection thresholds (electrical and heat). The pain threshold and the summation threshold to electrical stimuli and the summation threshold to heat stimuli increased significantly following treatment in both venlafaxine groups. In addition, the degree of the temporal summation to electrical and heat stimuli decreased significantly following treatment in both venlafaxine groups compared to the placebo. CONCLUSION: The study showed significant effect of venlafaxine in the manifestations of hyperalgesia and temporal summation, but not on the ongoing pain intensity. Furthermore, the quantitative sensory tests provided complementing information to the clinical measures.

Adult↗

Health-related quality of life and its predictive role for analgesic effect in patients with painful polyneuropathy.

Painful polyneuropathy is a common neuropathic pain condition. The present study describes health-related quality of life (HRQL) in a sample of patients with painful polyneuropathy of different origin and the possible predictive role of HRQL for analgesic effect. Ninety-three patients with a diagnosis of painful polyneuropathy were included in the analysis. Data were obtained from three randomised, placebo-controlled cross-over studies testing the effect of different drugs on polyneuropathic pain (St. John's wort, venlafaxine/imipramine and valproic acid). Patients completed a HRQL questionnaire (SF-36) after a drug-free baseline period and at the end of each treatment period. At baseline, all eight SF-36 scores were lower than in the normal population. No significant differences were found between SF-36 scales during placebo and treatment with valproic acid and St. John's wort. Those two drugs had not shown a pain relieving effect in former analysis. The SF-36 scale of bodily pain (BP) was improved by venlafaxine treatment (p=0.023). General health (GH) and vitality (VT) were improved under treatment with imipramine (GH: p=0.006, VT: p=0.015). In a multivariate logistic regression analysis, baseline SF-36 scores predicted subsequent response to pharmacological treatment. Results show an impaired HRQL in painful polyneuropathy and suggest that HRQL may predict response to analgesic treatment.

Adult↗

6"-Azidohex-2"-yne-cannabidiol: a potential neutral, competitive cannabinoid CB1 receptor antagonist.

Previous experiments with the mouse vas deferens have shown that cannabidiol produces surmountable antagonism of cannabinoid CB(1) receptor agonists at concentrations well below those at which it binds to cannabinoid CB(1) receptors and antagonizes alpha(1)-adrenoceptor agonists insurmountably. It also enhances electrically evoked contractions of this tissue. We have now found that subtle changes in the structure of cannabidiol markedly influence its ability to produce each of these effects, suggesting the presence of specific pharmacological targets for this non-psychoactive cannabinoid. Our experiments were performed with cannabidiol, 6"-azidohex-2"-yne-cannabidiol, abnormal-cannabidiol and 2'-monomethoxy- and 2',6'-dimethoxy-cannabidiol. Of these, 6"-azidohex-2"-yne-cannabidiol was as potent as cannabidiol in producing surmountable antagonism of (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (R-(+)-WIN55212) in vasa deferentia. However, it produced this antagonism with a potency that matched its cannabinoid CB(1) receptor affinity, suggesting that, unlike cannabidiol, it is a competitive cannabinoid CB(1) receptor antagonist. Moreover, since it did not enhance the amplitude of electrically evoked contractions, it may be a neutral cannabinoid CB(1) receptor antagonist.

Adenosine Triphosphate↗

Opioid and monoamine systems mediate the discriminative stimulus of tramadol in rats.

We analyzed the ability of the mu opioid peptide receptor ligands morphine and naloxone and several antidepressant drugs that are serotonin (fluoxetine), noradrenaline (reboxetine), mixed serotonin and noradrenaline (milnacipram and venlafaxine), dopamine (nomifensine) reuptake inhibitors, as well as roxindole (a nonselective drug) to substitute for, or alter, tramadol discrimination. Male Wistar rats were trained to discriminate tramadol (20 mg/kg) from saline in a two-choice water-reinforced paradigm. Out of the drugs studied, only morphine substituted for tramadol. In combination experiments, naloxone (0.1-1 mg/kg) attenuated the stimulus effects of tramadol (20 mg/kg) and the substitution evoked by morphine (2 mg/kg). Milnacipram (10 mg/kg) or reboxetine (10 mg/kg) enhanced the effects of tramadol (2.5-10 mg/kg); the other antidepressant drugs used failed to modulate tramadol discrimination. Our results indicate that tramadol can be used as a stimulus cue in rats, and that mu opioid peptide mechanisms are involved in its effects, while noradrenergic uptake inhibitors can enhance tramadol discrimination.

Adrenergic Uptake Inhibitors↗