<Emphasis Type="Italic">N</Emphasis>-Methyl-<Emphasis Type="SmallCaps">d</Emphasis>-aspartate receptors as a target for improved antipsychotic agents: novel insights and clinical perspectives

Rationale Activation of co-agonist N-methyl-d-aspartate (NMDA) and Glycine_B sites is mandatory for the operation of NMDA receptors, which play an important role in the control of mood, cognition and motor function.Objectives This article outlines the complex regulation of activity at Glycine_B/NMDA receptors by multiple classes of endogenous ligand. It also summarizes the evidence that a hypoactivity of Glycine_B/NMDA receptors contributes to the pathogenesis of psychotic states, and that drugs which enhance activity at these sites may possess antipsychotic properties.Results Polymorphisms in several genes known to interact with NMDA receptors are related to an altered risk for schizophrenia, and psychotic patients display changes in levels of mRNA encoding NMDA receptors, including the NR1 subunit on which Glycine_B sites are located. Schizophrenia is also associated with an overall decrease in activity of endogenous agonists at Glycine_B/NMDA sites, whereas levels of endogenous antagonists are elevated. NMDA receptor open channel blockers, such as phencyclidine, are psychotomimetic in man and in rodents, and antipsychotic agents attenuate certain of their effects. Moreover, mice with genetically invalidated Glycine_B/NMDA receptors reveal similar changes in behaviour. Finally, in initial clinical studies, Glycine_B agonists and inhibitors of glycine reuptake have been found to potentiate the ability of conventional antipsychotics to improve negative and, albeit modestly, cognitive and positive symptoms. In contrast, therapeutic effects of clozapine are not reinforced, likely since clozapine itself enhances activity at NMDA receptors.Conclusions Reduced activity at NMDA receptors is implicated in the aetiology of schizophrenia. Correspondingly, drugs that (directly or indirectly) increase activity at Glycine_B sites may be of use as adjuncts to other classes of antipsychotic agent. However, there is an urgent need for broader clinical evaluation of this possibility, and, to date, there is no evidence that stimulation of Glycine_B sites alone improves psychotic states.     

Glycine and <Emphasis Type="SmallCaps">d</Emphasis>-serine,but not <Emphasis Type="SmallCaps">d</Emphasis>-cycloserine,attenuate prepulse inhibition deficits induced by NMDA receptor antagonist MK-801

RATIONALE: Several agents that stimulate the glycine site of N-methyl-D: -aspartate (NMDA) receptors have been reported to moderately improve both negative symptoms and cognitive dysfunctions in patients with schizophrenia. However, differences in efficacy have also been reported, and further comparative pharmacological studies are still needed. OBJECTIVES: We aimed to explore the effects of two glycine site agonists of the NMDA receptor, glycine and D: -serine, and a partial agonist, D: -cycloserine, on prepulse inhibition (PPI) deficits induced by a NMDA receptor antagonist, MK-801, in mice. Furthermore, we performed in vivo microdialysis and additional PPI measurements using a selective glycine site antagonist to verify if the beneficial effects observed after the systemic administration of glycine were due to glycine itself via its activity at the glycine site. RESULTS: High doses of glycine (1.6 g/kg) and D: -serine (1.8 and 2.7 g/kg) significantly attenuated MK-801-induced PPI deficits. In contrast, D: -cycloserine did not show any amelioration of MK-801-induced PPI deficits at doses ranging from 7.5 mg/kg to 60 mg/kg. The selective glycine site antagonist, L-701,324 (10 mg/kg), antagonized the effect of glycine on MK-801-induced PPI deficits. Furthermore, in vivo microdialysis demonstrated that intraperitoneal injection of glycine significantly increased glycine and L: -serine levels, but decreased D: -serine levels in the prefrontal cortex. CONCLUSIONS: The findings of the present study suggest that glycine and D: -serine but not D: -cycloserine could attenuate PPI deficits associated with NMDA receptor hypofunction via NMDA glycine sites in the brain.     

Synthesis and evaluation of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkyl substituted chalcones as anti-cancer agents

Several new N,N-dialkyl substituted chalcones (chalconoids or benzylideneacetophenones) have been synthesized via the condensation of corresponding N,N-dialkylbenzaldehyde with various aryl methyl ketones. All the chalcones have been synthesized from readily available and cheap starting materials under environmentally benign conditions in very high yields without work up and column chromatographic purification. Synthesized compounds have been tested for their biological activity against pathogenic microorganisms such as Escherichia coli, Bacillus subtilis, and Mycobacterium smegmatis. Anti-cancer activity of these compounds has also been tested against multiple myeloma (RPMI-8226) and human mammary adenocarcinoma (MCF-7) cell lines. The most hydrophilic molecules 23 and 24 showed very good anti-cancer activity against MCF-7 cell lines at low micro-molar concentrations. All the compounds have also been evaluated for their activity against Beta-secretase 1 enzyme. One of the synthesized compounds showed Beta-secretase 1 enzyme inhibition activity at micro-molar concentration.     

Improvement of the extraction efficiency of <Emphasis Type="SmallCaps">d</Emphasis>-amygdalin from Armeniacae Semen powder through inactivating emulsin and suppressing the epimerization of <Emphasis Type="SmallCaps">d</Emphasis>-amygdalin

Armeniacae Semen contains not only amygdalin but also emulsin, which is an enzyme that hydrolyzes amygdalin. This hydrolysis reaction has been a major problem associated with the water extraction of Armeniacae Semen powder. In this study, the emulsin was inactivated by extracting Armeniacae Semen powder at a constant temperature of 90°C. In addition, in order to suppress the epimerization of d-amygdalin, the extraction time was kept to less than 8 min. The use of a 10 mM sodium phosphate buffer (pH 2.3) containing 13.5% acetonitrile as a mobile phase in reversed-phase HPLC was effective in separating and analyzing the d-amygdalin and neoamygdalin. The linearity between the concentrations and detector responses was obtained in the range of 0.05 to 0.5 mM. The detection limits for d-amygdalin and neoamygdalin were approximately 5 μM per amount injected.     

Synthesis and biological evaluation of some functionalized 1<Emphasis Type="Italic">H</Emphasis>-1,2,3-triazole tethered pyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>]pyridin-6(7<Emphasis Type="Italic">H</Emphasis>)-ones as antimicrobial and apoptosis inducing agents

A series of novel molecular hybrids containing pyrazole, pyridinone and 1,2,3-triazoles have been synthesized by one-pot four-component reaction of Meldrum’s acid, substituted aryl azides, 4-(prop-2-yn-1-yloxy)aryl aldehyde and 3-methyl-1-phenyl-1H-pyrazol-5-amine using L-proline as a basic organocatalyst besides CuSO₄.5H₂O and sodium ascorbate as catalysts for click chemistry in PEG-400 as a highly efficient and green media. Apoptosis studies have been carried out on ovarian follicles of goat (Capra hircus) and in vitro antibacterial activity has been done against six strains namely Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa and antifungal activity against two yeast strains namely, Candida albicans and Saccharomyces cerevisiae.     

Synthesis of 2-substituted-6-(4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-4-yl)benzo[<Emphasis Type="Italic">d</Emphasis>]oxazoles as potential anticonvulsant agents

A series of 2-substituted-6-(4H-1,2,4-triazol-4-yl)benzo[d]oxazoles were synthesized. The anticonvulsant effect and neurotoxicity of the compounds (intraperitoneally) were evaluated with the maximal electroshock (MES) test, subcutaneous pentylenetetrazole (sc-PTZ), and rotarod tests in mice. 2-Phenyl-6-(4H-1,2,4-triazol-4-yl)benzo[d]oxazole (3g) was the most active and also had the lowest toxicity. In the anti-MES potency test, it showed median effective dose (ED₅₀) of 29.5 mg/kg, a median toxicity dose (TD₅₀) of 285 mg/kg, and a protective index (PI) of 9.7, which is greater than the reference drug, carbamazepine, which has a PI of 6.4.     

<Emphasis Type="SmallCaps">d</Emphasis>-Cycloserine and performance under different states of anxiety in healthy volunteers

Rationale There is interest in the development of augmentation therapy in the treatment of anxiety disorders. Recent publications have shown that d-cycloserine can benefit exposure therapy in a group of acrophobic (height phobic) subjects and in patients with social anxiety disorder. These studies were based on the animal data suggesting that drugs acting to enhance glutamate function may be developed to accelerate the behavioural treatment of anxiety disorders. Perhaps by enhancing glutamate/N-methyl-d-aspartate receptor function, learning is thus enhanced. This study examines the effects of d-cycloserine 50 mg on a task that involves learning. We manipulated anxiety levels to model the effects of high anxiety. Objectives To evaluate performance and learning, we used the Manikin task. Two groups of 24 healthy volunteers participated in a double-blind, placebo-controlled study. One group received the inhalation of CO₂ 7.5% to model high anxiety, and the second group received air to represent lower anxiety. Subjects received d-cycloserine 50 mg or placebo, and the Manikin task was performed during the gas inhalation. Results There were significant differences in the group inhaling air, but not CO₂, with the d-cycloserine group showing an increase in correct responses. This difference was apparent at several time blocks during the 20-min task. These findings were supported by subjective measures in that participants who received d-cycloserine reported that the task was easier. Conclusions We have shown that at lower anxiety levels, d-cycloserine 50 mg improved the performance of this challenging visuospatial cognitive task. This increase in performance was not seen when anxiety was higher, and d-cycloserine did not appear to increase subjective anxiety. These data lend support to the use of d-cycloserine and related glutamate enhancers as cognitive modulators and suggest that the actions of d-cycloserine are not simply related to increased arousal or anxiety.     

Subjective and physiological effects of acute intranasal methamphetamine during <Emphasis Type="SmallCaps">d</Emphasis>-amphetamine maintenance

Rationale  

Methamphetamine abuse and dependence are significant public-health concerns. Behavioral therapies are effective for reducing methamphetamine use. However, many patients enrolled in behavioral therapies are unable to achieve significant periods of abstinence, suggesting other strategies like pharmacotherapy are needed.     

NMDA receptor modulation by <Emphasis Type="SmallCaps">d</Emphasis>-cycloserine promotes episodic-like memory in mice

Rationale NMDA-R (N-methyl-d-aspartate receptors) have been implicated in synaptic plasticity underlying one-trial learning of event-place associations. In rodents, episodic-like memory (ELM) of personally experienced events can be inferred from behavior that reflects the remembrance of the content (what kind of object was presented), place (where was this object placed), and temporal context (when was the object presented). We have previously shown that that d-cycloserine (DCS), an NMDA-R agonist, ameliorates stress-induced deficits in ELM. Objectives In this study, we used an experimental protocol designed to detect promnestic drug effects and investigated whether DCS, which is known to enhance learning and memory, can induce ELM under conditions where mice normally do not show ELM. Results Mice that have been treated i.p. with DCS (20 mg/kg) both remembered the temporal order in which two different objects had been encountered during two consecutive sample trials, as well as their spatial position during the sample trials. Most importantly, the test trial performance of these mice is compatible with ELM in terms of an integrated memory for unique experiences comprising “what”, “where”, and “when” information. In contrast, mice that have received either a saline injection or lower doses of DCS (0.2 and 2.0 mg/kg) did not show such an integrated ELM. Conclusions To our knowledge, this is the first report showing that DCS can promote ELM in mice.     

Effects of low-dose <Emphasis Type="SmallCaps">d</Emphasis>-serine on recognition and working memory in mice

Rationale  

d-Serine is an endogenous co-agonist of the N-methyl-d-aspartate (NMDA) receptor and has been suggested to improve cognitive deficits in schizophrenia.     

The effect of <Emphasis Type="Italic">d</Emphasis>,<Emphasis Type="Italic">l</Emphasis>-methamphetamine on simulated driving performance

Rationale  

Illicit drugs such as methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. The exact effect of methamphetamine or its specific isomers on driving and driving behaviour have yet to be thoroughly investigated.     

Essential oil compounds from<Emphasis Type="Italic">Agastache rugosa</Emphasis> as antifungal agents against<Emphasis Type="Italic">Trichophyton</Emphasis> species

The antifungal activities of the essential oil from Agastache rugosa and its main component, estragole, combined with ketoconazole, one of the azole antibiotics commonly used to treat infections caused by Trichophyton species, were evaluated in this study. The combined effects were measured by the checkerboard microtiter and the disk diffusion tests, against T. erinacei, T. mentagrophytes, T. rubrum, T. schoenleinii and T. soudanense. Susceptibility of the five Trichophyton species to the oil alone, or ketoconazole alone, differed distinctly. The fractional inhibitory concentration indices (FICI) of ketoconazole combined with estragole or A. rugosa essential oil, against the tested Trichophyton species, were between 0.05 and 0.27, indicating synergistic effects. These drug combinations exhibited the most significant synergism against T. mentagrophytes, with FICIs of 0.05 and 0.09 for estragole and the essential oil fraction from A. rugosa, respectively. Isobolograms based on the data from checkerboard titer tests also indicated significant synergism between ketoconazole and the Agastache oil fraction or estragole, against the Trichophyton species evaluated. Trichophyton susceptibility to ketoconazole was significantly improved by combination with the Agastache rugosa oil fraction or its main component, estragole.     

Effects of <Emphasis Type="Italic">Bidens pilosa</Emphasis> L. var. <Emphasis Type="Italic">radiata</Emphasis> S<Emphasis Type="SmallCaps">cherff</Emphasis> on experimental gastric lesion

Bidens pilosa L. var. radiata Scherff (BP) is a plant used as a traditional folk medicine. BP, cultivated with only green manure on Miyako Island, Okinawa prefecture, was processed to powder and is referred to as MMBP. We have reported that MMBP has antioxidant, anti-inflammatory, and anti-allergy properties. In this study, we investigated the effects of MMBP on several experimental gastric lesions induced by HCl/EtOH, a non-steroidal anti-inflammatory drug, or cold-restraint stress, comparing these results with those of rutin or anti-ulcerogenic drugs (cimetidine or sucralfate) based on the lesion index and hemorrhage from the gastric lesions. Orally administered MMBP prevented the progression of the gastric lesions. Moreover, treatment with MMBP, rutin, or sucralfate, which had potent antioxidative activity, inhibited increases in the levels of thiobarbituric acid reactive substances (TBARS) in the gastric mucosal lesions. The inhibition of the gastric mucosal TBARS content by MMBP may have been due to the antioxidant effects of MMBP. These results indicate that MMBP prevents the progression of acute gastric mucosal lesions, possibly by suppressing oxidative stress in the gastric mucosa.     

Two new antibacterial norabietane diterpenoids from cyanobacteria, <Emphasis Type="Italic">Microcoleous </Emphasis><Emphasis Type="Italic">lacustris</Emphasis>

Two abietane diterpenes were isolated from cyanobacteria Microcoleous lacustris, 20-nor-3α-acetoxyabieta-5,7,9,11,13-pentaene and 20-nor-3α-acetoxy-12-hydroxy-abieta-5,7,9,11,13-pentaene. These compounds were assayed against Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhi, Vibrio cholerae, Bacillus subtilis, Bacillus cereus, Escherichia coli, and Klebsiella pneumoniae. Both compounds showed activity against S. aureus, S. epidermidis, S. typhi, and V. cholerae, but not against the other bacteria.     

Differential effects of the <Emphasis Type="SmallCaps">d-</Emphasis> and <Emphasis Type="SmallCaps">l-</Emphasis> isomers of amphetamine on pharmacological MRI BOLD contrast in the rat

Rationale

The d- and l-amphetamine sulphate isomers are used in the formulation of Adderall XR®, which is effective in the treatment of attention-deficit hyperactivity disorder (ADHD). The effects of these isomers on brain activity has not been examined using neuroimaging.

Objectives

This study determines the pharmacological magnetic resonance imaging blood-oxygenation-level-dependent (BOLD) response in rat brain regions after administration of each isomer.

Materials and methods

Rats were individually placed into a 2.35 T Bruker magnet for 60 min to achieve basal recording of variation in signal intensity. Either saline (n?=?9), d-amphetamine sulphate (2 mg/kg, i.p.; n?=?9) or l-amphetamine sulphate (4 mg/kg, i.p.; n?=?9) were administered, and recording continued for a further 90 min. Data were analysed for BOLD effects using statistical parametric maps. Blood pressure, blood gases and respiratory rate were monitored during scanning.

Results

The isomers show overlapping effects on the BOLD responses in areas including nucleus accumbens, medial entorhinal cortex, colliculi, field CA1 of hippocampus and thalamic nuclei. The l-isomer produced greater global changes in the positive BOLD response than the d-isomer, including the somatosensory and motor cortices and frontal brain regions such as the orbitofrontal cortices, prelimbic and infralimbic cortex which were not observed with the d-isomer.

Conclusions

The amphetamine isomers produce different BOLD responses in brain areas related to cognition, pleasure, pain processing and motor control probably because of variations on brain amine systems such as dopamine and noradrenaline. The isomers may, therefore, have distinct actions on brain regions affected in ADHD patients.

     

Hypermagnesemia disturbances in rats,NO-related: pentadecapeptide BPC 157 abrogates, <Emphasis Type="SmallCaps">l</Emphasis>-NAME and <Emphasis Type="SmallCaps">l</Emphasis>-arginine worsen

Aim

Stable gastric pentadecapeptide BPC 157, administered before a high-dose magnesium injection in rats, might be a useful peptide therapy against magnesium toxicity and the magnesium-induced effect on cell depolarization. Moreover, this might be an NO-system-related effect. Previously, BPC 157 counteracts paralysis, arrhythmias and hyperkalaemia, extreme muscle weakness; parasympathetic and neuromuscular blockade; injured muscle healing and interacts with the NOS-blocker and NOS-substrate effects.

Main methods

Assessment included magnesium sulfate (560 mg/kg intraperitoneally)-induced muscle weakness, muscle and brain lesions, hypermagnesemia, hyperkalaemia, increased serum enzyme values assessed in rats during and at the end of a 30-min period and medication (given intraperitoneally/kg at 15 min before magnesium) [BPC 157 (10 µg, 10 ng), l-NAME (5 mg), l-arginine (100 mg), alone and/or together]. In HEK293 cells, the increasing magnesium concentration from 1 to 5 mM could depolarize the cells at 1.75 ± 0.44 mV.

Key findings

l-NAME + magnesium-rats and l-arginine + magnesium-rats exhibited worsened severe muscle weakness and lesions, brain lesions, hypermagnesemia and serum enzymes values, with emerging hyperkalaemia. However, l-NAME + l-arginine + magnesium-rats exhibited all control values and normokalaemia. BPC 157 abrogated hypermagnesemia and counteracted all of the magnesium-induced disturbances (including those aggravated by l-NAME or l-arginine). Thus, cell depolarization due to increasing magnesium concentration was inhibited in the presence of BPC 157 (1 µM) in vitro.

Significance

BPC 157 likely counteracts the initial event leading to hypermagnesemia and the life-threatening actions after a magnesium overdose. In contrast, a worsened clinical course, higher hypermagnesemia, and emerging hyperkalaemia might cause both l-NAME and l-arginine to affect the same events adversely. These events were also opposed by BPC 157.

     

Discriminative stimulus and reinforcing effects of <Emphasis Type="Italic">p</Emphasis>-fluoro-<Emphasis Type="SmallCaps">l</Emphasis>-deprenyl in monkeys

Rationale para-Fluoro-l-deprenyl (Fludepryl), a halogenated derivative of l-deprenyl, shares structural similarities with amphetamine and may have potential as a medication for psychostimulant abuse. Objectives p-Fluoro-l-deprenyl was evaluated for psychomotor stimulant, discriminative stimulus, and reinforcing effects in squirrel monkeys. Methods One group of monkeys was trained under a ten-response fixed-ratio (FR10) schedule of stimulus termination to discriminate between methamphetamine (0.32 mg/kg, i.m.) and saline. Other monkeys were trained to self-administer i.v. cocaine under either a simple FR10 schedule or a second-order fixed-interval 5-min schedule with FR10 components. Results Full generalization to the methamphetamine-training stimulus was produced by an i.m. dose of 10.0 mg/kg p-fluoro-l-deprenyl. l-Deprenyl and the metabolites of p-fluoro-l-deprenyl, p-fluoro-l-amphetamine, and p-fluoro-l-methylamphetamine were more potent, producing full generalization at doses of 1.0–3.2 mg/kg. Under the FR10 schedule of drug injection, persistent self-administration behavior was maintained by i.v. cocaine injections but not by injections of vehicle or injection doses of p-fluoro-l-deprenyl up to 1.0 mg/kg. However, p-fluoro-l-deprenyl did maintain moderate levels of i.v. self-administration responding under the second-order schedule of drug injection. Peak response rates maintained by 0.1-mg/kg injections of p-fluoro-l-deprenyl were significantly greater than those associated with saline substitution, yet significantly lower than those maintained by cocaine or d-amphetamine. Conclusions p-Fluoro-l-deprenyl has methamphetamine-like discriminative-stimulus properties in squirrel monkeys that appear at higher doses than for its parent compound, l-deprenyl. It also appears to function as a relatively limited reinforcer of intravenous self-administration behavior in monkeys trained to self-administer i.v. cocaine.     

Identification of <Emphasis Type="Italic">N</Emphasis>-arylsulfonylpyrimidones as anticancer agents

For confirming the role of five membered ring of imidazolidinone moiety of N-arylsulfonylimidazolidinones (7) previously reported with highly potent anticancer agent, a series of N-arylsulfonylpyrimidones (10a–g) and N-arylsulfonyltetrahydropyrimidones (11a–e) were prepared and their anti-proliferating activity was measured against human cancer cell lines (renal ACHN, colon HCT-15, breast MDA-MB-231, lung NCI-H23, stomach NUGC-3, and prostate PC-3) using XTT assay. Among them, 1-(1-acetylindolin-5-ylsulfonyl)-4-phenyltetrahydropyrimidin-2(1H)-one (11d, mean GI₅₀ = 3.50 µM) and ethyl 5-(2-oxo-4-phenyltetrahydropyrimidin-1(2H)-ylsulfonyl)-indoline-1-carboxylate (11e, mean GI₅₀ = 0.26 µM) showed best growth inhibitory activity against human cancer cell lines. Considering the activity results, N-arylsulfonyltetrahydropyrimidones (11) exhibited more potent activity compared to N-arylsulfonylpyrimidones (10) and comparable activity to N-arylsulfonylimidazolidinones (7). Especially, tetrahydropyrimidin-2(1H)-one analogs containing acylindolin-5-ylsulfonyl moiety at position 1 demonstrated their strong growth inhibitory activity against human cancer cell lines.     

Synthesis and biological activity of <Emphasis Type="Italic">o</Emphasis>-isobornylphenol derivatives

Hemorheological and antiaggregant properties of new o-isobornylphenol derivatives were investigated in ex vivo experiments. 4-Methyl-2,6-diisobornylphenol and 2-(dibutylamino)methyl-4-methyl-6-isobornylphenol hydrochloride demonstrated the maximum hemorheological activity. After intragastric administration, these compounds decreased the blood viscosity at low shear rates, suppressed the development of blood “hyperviscosity” before incubation (20.0 ± 0.4°C, 1 h), and reduced ADP-induced (4 × 10^–6 M) aggregation of platelets. The hemorheological and antiaggregant effects of the investigated compounds were comparable to those of pentoxifylline.