Effects of sarizotan in animal models of ADHD: challenging pharmacokinetic-pharmacodynamic relationships.

Sarizotan 1-[(2R)-3,4-dihydro-2H-chromen-2-yl]-N-[[5-(4-fluorophenyl) pyridin-3-yl]methyl] methenamine, showed an in vivo pharmaco-EEG profile resembling that of methylphenidate which is used in attention deficit/hyperactivity disorder (ADHD). In turn, we tested sarizotan against impulsivity in juvenile rats measuring the choice for large delayed vs. a small immediate reward in a T-maze and obtained encouraging results starting at 0.

Using cholinergic M1 receptor positive allosteric modulators to improve memory via enhancement of brain cholinergic communication.

Benzylquinolone carboxylic acid (BQCA) is a recently described cholinergic muscarinic M(1) receptor positive allosteric modulator having potential as cognitive enhancer in dementia. The present study focused on the characterisation of BQCA's mode of action in relation to positive effects on memory and side-effects in an animal model. To get insight into this mode of action, in vitro receptor potency/left shift experiments in cells stably expressing the rat's M(1) receptor were performed.

Effect of 5-HT5A antagonists in animal models of schizophrenia, anxiety and depression.

The few available data on the pharmacological effect of 5-HT5A receptors suggest that antagonists may have anxiolytic, antidepressant and antipsychotic activity. The aim of our study was to verify these suggestions in relevant animal models. Two 5-HT5A antagonist ligands, SB-699551-A (N-[2-(dimethylamino)ethyl]-N-[[4'-[[(2-phenylethyl)amino]methyl][1,1'-biphenyl]-4-yl]methyl]cyclopentanepropanamide dihydrochloride) (3-60 mg/kg, intraperitoneally) and A-843277 (N-(2,6-dimethoxybenzyl)-N'[4-(4-fluorophenyl)thiazol-2-yl]guanidine) (3-30 mg/kg, intraperitoneally), were examined in the open-field test, in a foot-shock-induced ultrasonic vocalization test, in the forced swim test (FST) and in the amphetamine-induced and phencyclidine-induced hyperlocomotion tests to examine their effect on general behavioural patterns, and their anxiolytic-like, antidepressant-like and antipsychotic-like properties, respectively.

Potency, voltage-dependency, agonist concentration-dependency, blocking kinetics and partial untrapping of the uncompetitive N-methyl-D-aspartate (NMDA) channel blocker memantine at human NMDA (GluN1/GluN2A) receptors.

Both the clinical tolerability and the symptomatic effects of memantine in the treatment of Alzheimer's disease have been attributed to its moderate affinity (IC(50) around 1 microM at -70 mV) for NMDA receptor channels and associated fast, double exponential blocking/unblocking kinetics and strong voltage-dependency. Most of these biophysical data have been obtained from rodent receptors. Some substances show large species-specific differences, so using human rather than rodent receptors and tissue may highlight important differences in the effects of drugs.

Blocking kinetics of memantine on NR1a/2A receptors recorded in inside-out and outside-out patches from Xenopus oocytes.

Previous experiments on primary cultures of hippocampal/cortical neurones revealed that the block and unblock of N-Methyl-D-Aspartate (NMDA) receptor channels by memantine showed double exponential kinetics and that the offset kinetics following a voltage-step were much faster than following a concentration jump. There are, however, two major problems when using such cultured primary neurones for these experiments (1) the almost certain expression of heterogeneous NMDA receptor subunits which could underlie double exponential kinetics due to different potencies at receptor subtypes and (2) slow space- and concentration-clamp due to neuronal morphology which could mask even faster kinetics. Therefore, we performed similar experiments with Xenopus oocytes exclusively expressing one NMDA receptor type (NR1a/2A) at high levels which allowed recordings from membrane patches with large currents.

Memantine does not show intracellular block of the NMDA receptor channel.

Mg2+ is known to gain access to the NMDA receptor channel from both the extra- and intracellular compartments. Memantine, being an amphiphilic substance, reaches intracellular concentrations of approximately 30 microM, which are much higher than therapeutic extracellular concentrations ( approximately 1 microM). We therefore investigated whether memantine can also block the NMDA receptor channel from the intracellular compartment.

Characterization of vascular reactivity in dorsal hand veins after oral rosiglitazone treatment in healthy subjects.

Objective: In clinical studies with diabetic patients thiazolidinediones have been shown to restore abnormal vascular function which might be attributed to improved blood sugar control or to restoration of vascular endothelium and smooth muscle responsiveness. The present study was undertaken to investigate whether rosiglitazone modulates vascular responsiveness to different vasoactive agents and exerts renin-angiotensin-system (RAS)-inhibiting properties in healthy subjects in vivo.

Methods: 24 healthy male subjects were randomized to receive either rosiglitazone or placebo.

Positive and negative modulation of group I metabotropic glutamate receptors.

A discriminating pharmacophore model for noncompetitive metabotropic glutamate receptor antagonists of subtype 1 (mGluR1) was developed that facilitated the discovery of moderately active mGluR1 antagonists. One scaffold was selected for the design of several focused libraries where different substitution patterns were introduced. This approach facilitated the discovery of potent mGluR1 antagonists, as well as positive and negative mGluR5 modulators, because both receptor subtypes share similar binding pockets.

A novel class of amino-alkylcyclohexanes as uncompetitive, fast, voltage-dependent, N-methyl-D-aspartate (NMDA) receptor antagonists--in vitro characterization.

The fact that potent NMDA receptor channel blockers produce phencyclidine-like psychotropic symptoms in man and rodents implies that uncompetitive antagonism of NMDA receptors may not be a promising therapeutic approach. However, recent data indicate that agents with moderate affinity such as memantine and neramexane (MRZ 2/579) are useful therapeutics due to their strong voltage-dependency and rapid unblocking kinetics. Merz has developed a series of novel uncompetitive NMDA receptor antagonists based on an amino-alkylcyclohexane structure.

Agonist concentration dependency of blocking kinetics but not equilibrium block of N-methyl-D-aspartate receptors by memantine.

Memantine is an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist which is registered in both Europe and the USA for the treatment of Alzheimer's disease (AD). Cultured rat hippocampal neurons were used to evaluate the potency and blocking kinetics of this therapeutically very well-tolerated agent in the presence of various concentrations of the synthetic agonist NMDA and a constant, saturating concentration of the co-agonist D-serine (10 microM). Whole-cell patch-clamp experiments at -70 mV revealed that the degree of "equilibrium" blockade of NMDA-induced currents by memantine was largely unaffected by the concentration of the agonist NMDA.

Water-soluble rylene dyes as high-performance colorants for the staining of cells.

The synthesis of perylene and terrylene chromophores carrying a single poly(ethylene oxide) chain is presented. These chromophores reveal a strong solvatochromic behavior: High fluorescence in nonpolar solvents and weak fluorescence in polar solvents which is mainly attributed to aggregation. Therefore, such chromophores are attractive candidates as sensitive fluorescent probes reflecting the polarity of their environment.

Block of AMPA receptor desensitization by a point mutation outside the ligand-binding domain.

Desensitization of ionotropic glutamate receptors (GluRs), specifically the AMPA receptor subtype, shapes the postsynaptic response at certain synapses in the brain. All known mechanisms that alter desensitization, either pharmacological or mutational, are associated with the ligand-binding domain. Here we report that substitution of a conserved positively charged arginine (R) with a negatively charged glutamate in the linker between the pore-forming M3 segment and the S2 lobe, a region outside the ligand-binding domain, blocks desensitization in homomeric AMPA receptors composed of GluR-B(i) subunits.

Extracellular vestibule determinants of Ca2+ influx in Ca2+-permeable AMPA receptor channels.

At certain synapses in the brain, Ca2+-permeable AMPA receptor (AMPAR) channels represent an important pathway for synaptically controlled Ca2+ entry. However, the molecular determinants of this Ca2+ influx are poorly defined. In NMDA receptor (NMDAR) channels, where the influx is much greater, the extracellular vestibule, specifically the M3 segment and regions C-terminal to it in the NR1 subunit, contains elements critical to their high Ca2+ influx under physiological conditions.

Voltage and concentration dependence of Ca(2+) permeability in recombinant glutamate receptor subtypes.

The channels associated with glutamate receptor (GluR) subtypes, namely N-methyl-D-aspartate receptors (NMDARs), and Ca(2+)-permeable alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPARs) and kainate receptors (KARs), are to varying degrees permeable to Ca(2+). To compare the mechanism of Ca(2+) influx, we measured Ca(2+) permeability relative to that of Na(+) (P(Ca)/P(Na)) using fractional Ca(2+) currents (P(f)) and reversal potential measurements over a wide voltage and Ca(2+) concentration range in recombinant NMDAR NR1-NR2A, AMPAR GluR-A(Q) and KAR GluR-6(Q) channels. For NR1-NR2A channels, P(Ca)/P(Na) derived from P(f) measurements was voltage independent but showed a weak concentration dependence.

The Lurcher mutation identifies delta 2 as an AMPA/kainate receptor-like channel that is potentiated by Ca(2+).

Neurodegeneration in Lurcher (Lc) mice results from constitutive activation of delta 2, a subunit of ionotropic glutamate receptors (GluRs) with unknown natural ligands and channel properties. Homo-oligomeric channels of GluR-delta2 with the Lurcher mutation (GluR-delta 2(Lc)) expressed in human embryonic kidney 293 cells showed a doubly rectifying current-voltage relation reminiscent of the block by intracellular polyamines in AMPA/kainate channels. Similarly, the fraction of the total current carried by Ca(2+) was approximately 2-3%, comparable with that found in Ca(2+)-permeable AMPA/kainate channels.

Stability and binding properties of wild-type and c17s mutated human sterol carrier protein 2.

The temperature- and solvent-induced denaturation of both the SCP2 wild-type and the mutated protein c71s were studied by CD measurements at 222 nm. The temperature-induced transition curves were deconvoluted according to a two-state mechanism resulting in a transition temperature of 70.5 degrees C and 59.

Thermodynamic stability of annexin V E17G: equilibrium parameters from an irreversible unfolding reaction.

Conformational stability of the membrane-binding protein annexin V E17G has been determined by high-sensitivity differential scanning microcalorimetry (DSC) measurements and by isothermal, guanidinium hydrochloride (GdnHCl)-induced unfolding studies. Wild-type annexin V and the E17G mutant protein studied here are structurally almost identical. Therefore, it can be expected that the present results will not deviate significantly from the stability data of the wild-type molecule.