Constructing Large 2D Lattices Out of DNA-Tiles.

The predictable nature of deoxyribonucleic acid (DNA) interactions enables assembly of DNA into almost any arbitrary shape with programmable features of nanometer precision. The recent progress of DNA nanotechnology has allowed production of an even wider gamut of possible shapes with high-yield and error-free assembly processes. Most of these structures are, however, limited in size to a nanometer scale. To overcome this limitation, a plethora of studies has been carried out to form larger structures using DNA assemblies as building blocks or tiles. Therefore, DNA tiles have become one of the most widely used building blocks for engineering large, intricate structures with nanometer precision. To create even larger assemblies with highly organized patterns, scientists have developed a variety of structural design principles and assembly methods. This review first summarizes currently available DNA tile toolboxes and the basic principles of lattice formation and hierarchical self-assembly using DNA tiles. Special emphasis is given to the forces involved in the assembly process in liquid-liquid and at solid-liquid interfaces, and how to master them to reach the optimum balance between the involved interactions for successful self-assembly. In addition, we focus on the recent approaches that have shown great potential for the controlled immobilization and positioning of DNA nanostructures on different surfaces. The ability to position DNA objects in a controllable manner on technologically relevant surfaces is one step forward towards the integration of DNA-based materials into nanoelectronic and sensor devices.

Creation of ordered 3D tubes out of DNA origami lattices.

Hierarchical self-assembly of nanostructures with addressable complexity has been a promising route for realizing novel functional materials. Traditionally, the fabrication of such structures on a large scale has been achievable using top-down methods but with the cost of complexity of the fabrication equipment versus resolution and limitation mainly to 2D structures. More recently bottom-up methods using molecules like DNA have gained attention due to the advantages of low fabrication costs, high resolution and simplicity in an extension of the methods to the third dimension. One of the more promising bottom-up techniques is DNA origami due to the robust self-assembly of arbitrarily shaped nanostructures with feature sizes down to a few nanometers. Here, we show that under specific ionic conditions of the buffer, the employed plus-shaped, blunt-ended Seeman tile (ST) origami forms elongated, ordered 2D lattices, which are further rolled into 3D tubes in solution. Imaging structures on a surface by atomic force microscopy reveals ribbon-like structures, with single or double layers of the origami lattice. Further studies of the double-layered structures in a liquid state by confocal microscopy and cryo-TEM revealed elongated tube structures with a relatively uniform width but with a varying length. Through meticulous study, we concluded that the assembly process of these 3D DNA origami tubes is heavily dependent on the concentration of both mono- and divalent cations. In particular, nickel seems to act as a trigger for the formation of the tubular assemblies in liquid.

Covalent and non-covalent coupling of a Au102 nanocluster with a fluorophore: energy transfer, quenching and intracellular pH sensing.

Interactions between an atomically precise gold nanocluster Au102(p-MBA)44 (p-MBA = para mercaptobenzoic acid) and a fluorescent organic dye molecule (KU, azadioxatriangulenium) are studied. In solution, the constituents form spontaneously a weakly bound complex leading to quenching of fluorescence of the KU dye via energy transfer. The KU can be separated from the complex by lowering pH, leading to recovery of fluorescence, which forms a basis for an optical reversible pH sensor. However, the sensor is not a stable entity, which could be delivered inside cells. For this purpose, a covalently bound hybrid is synthesized by linking the KU dye to the ligand layer of the cluster via an ester bond. Covalent linking facilitates entry of the cluster-dye hybrids into cells via endocytosis. Inside cells, the hybrids accumulate in endosomes where Au102 releases its cargo via hydrolysis of the ester bond. Changes of the local pH inside endosomes regulate reversible fluorescence due to variations in the interactions between the Au102 cluster and the dye. This work presents a concept for delivering reporter molecules into cells by using atomically precise gold nanoclusters as carriers and paves the way for future developments of cluster-reporter sensors for in vivo measurements of e.g. absolute pH values or ion concentrations.

Neurochemical and Behavioral Effects of a New Hallucinogenic Compound 25B-NBOMe in Rats.

4-Bromo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25B-NBOMe) is a hallucinogen exhibiting high binding affinity for 5-HT2A/C serotonin receptors. In the present work, we investigated its effect on dopamine (DA), serotonin (5-HT), acetylcholine (ACh), and glutamate release in the rat frontal cortex, striatum, and nucleus accumbens. Hallucinogenic activity, impact on cognitive and motor functions, and anxiogenic/anxiolytic properties of this compound were also tested. The release of DA, 5-HT, ACh, and glutamate was studied using microdialysis in freely moving animals. Hallucinogenic activity was investigated using head and body twitch response (WDS), cognitive functions were examined with the novel object recognition test (NOR), locomotor activity was studied in the open field (OF), while anxiogenic/anxiolytic effect was tested using the light/dark box (LDB). Neurotoxicity was evaluated with the comet assay. 25B-NBOMe increased DA, 5-HT, and glutamate release in all studied brain regions, induced hallucinogenic activity, and lowered the recognition index (Ri) vs. control in the NOR test. It also decreased locomotor activity of rats in the OF test. The effect of 25B-NBOMe in the NOR test was inhibited by scopolamine. In the LDB test, the time spent in the dark zone was longer in comparison to control and was dose-dependent. In contrast to MDMA, 25B-NBOMe showed subtle genotoxic effect observed in the comet assay.Our findings indicate that 25B-NBOMe shows hallucinogenic activity in the wide range of doses. The changes in neurotransmitter levels may be related to 25B-NBOMe affinity for 5-HT2A receptor. Alterations in the NOR, OF, and LDB indicate that 25B-NBOMe impacts short-term memory, locomotion, and may be anxiogenic.

Chemically Selective Imaging of Individual Bonds through Scanning Electron Energy-Loss Spectroscopy: Disulfide Bridges Linking Gold Nanoclusters.

As proof-of-principle of chemically selective, spatially resolved imaging of individual bonds, we carry out electron energy-loss spectroscopy in a scanning transmission electron microscopy instrument on atomically precise, thiolate-coated gold nanoclusters linked with 5,5'-bis(mercaptomethyl)-2,2'-bipyridine dithiol ligands. The images allow the identification of bridging disulfide bonds (R-S-S-R) between clusters, and X-ray photoelectron spectra support the finding.

Sensitivity to negative and positive feedback as a stable and enduring behavioural trait in rats.

RATIONALE: According to psychological theories, cognitive distortions play a pivotal role in the aetiology and recurrence of mood disorders. Although clinical evidence for the coexistence of depression and altered sensitivity to performance feedback is relatively coherent, we still do not know whether increased or decreased sensitivity to positive or negative feedback is associated with 'pro-depressive' profile in healthy subjects. OBJECTIVE: Our research has been designed to answer this question, and here, we present the first steps in that direction. METHODS: Using a rat version of the probabilistic reversal-learning (PRL) paradigm, we evaluated how sensitivity to negative and positive feedback influences other cognitive processes associated with mood disorders, such as motivation in the progressive ratio schedule of reinforcement (PRSR) paradigm, hedonic status in the sucrose preference (SP) test, locomotor and exploratory activity in the open field (OF) test, and anxiety in the light/dark box (LDB) test. RESULTS: The results of our study demonstrated for the first time that in rodents, sensitivity to negative and positive feedback could be considered a stable and enduring behavioural trait. Importantly, we also showed that these traits are independent of each other and that trait sensitivity to positive feedback is associated with cognitive flexibility in the PRL test. The computational modelling results also revealed that in animals classified as sensitive to positive feedback, the α learning rates for both positive and negative reward prediction errors were higher than those in animals classified as insensitive. We observed no statistically significant interactions between sensitivity to negative or positive feedback and the parameters measured in the PRSR, SP, OF or LDB tests. CONCLUSIONS: Further studies using animal models of depression based on chronic stress should reveal whether sensitivity to feedback is a latent trait that when interacts with stressful life events, could produce correlates of depressive symptoms in rats.

Correction to: the Effects of Exposure to Mephedrone During Adolescence on Brain Neurotransmission and Neurotoxicity in Adult Rats.

Acknowledgments: This study was supported by the Grant No 2013/09/B/NZ7/04104 from the National Science Center (Poland).

Effects of exposure to 5-MeO-DIPT during adolescence on brain neurotransmission and neurotoxicity in adult rats.

PURPOSE: Tryptamine hallucinogen 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is a serotonin transporter inhibitor with high affinity for serotonin 5-HT1A and 5-HT2A/C receptors. We showed previously that 5-MeO-DIPT in a single dose increased neurotransmitter release in brain regions of rats and elicited single- and double-strand DNA breaks. Herein we investigated the effects of repeated-intermittent 5-MeO-DIPT administration in adolescence on dopamine (DA), serotonin (5-HT) and glutamate release in brain regions of adult rats. Furthermore, we examined caspase-3 activity, oxidative DNA damage, the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels, and cell viability. METHODS: Neurotransmitter release was measured by microdialysis in freely moving animals. Caspase-3 activity was assessed colorimetrically, and oxidative DNA damage with the comet assay, while the Gpx3, Sod1, Ht1a and Ht2a mRNA expression levels were assessed by real-time polymerase chain reaction. Cell viability was studied in SH-SY5Y and Hep G2 cells by the MTT test. RESULTS: We observed changed responses of DA, 5-HT and glutamate neurons to a challenge dose of 5-MeO-DIPT when animals were treated repeatedly in adolescence with this hallucinogen. The basal extracellular levels of DA and 5-HT were decreased in the striatum and nucleus accumbens, while glutamate level was increased in the nucleus accumbens and frontal cortex. The damage of cortical DNA, increased Gpx3 and Sod1 mRNA expression and affected caspase-3 activity were also observed. Furthermore, decreased Ht1a and Ht2a mRNA expression in the frontal cortex and marked cytotoxicity of 5-MeO-DIPT were found. CONCLUSIONS: These results suggest that 5-MeO-DIPT given repeatedly during adolescence affects brain neurotransmission and shows neurotoxic potential observed in adult animals.

Dithiol-Induced Oligomerization of Thiol-Protected Gold Nanoclusters.

Controlled synthesis of nanostructure oligomers requires detailed understanding of their wet chemistry and the forces driving the polymerization process. In this paper, we report the main factors affecting the reaction yields of a dithiol-induced synthesis of covalently bound nanocluster dimers and oligomers and present a detailed analysis of possible reaction mechanisms. We synthesize the nanocluster oligomers using monodisperse para-mercaptobenzoic acid (p-MBA)-protected gold nanoclusters with a nominal composition of Au∼250(p-MBA) n to minimize ensemble effects on size, shape, and surface structure. Ligand exchange was performed on the nanoclusters with five different dithiol linkers: 5,5'-bis(mercaptomethyl)-2,2'-bipyridine, 4,4″-thiobisbenzenethiol, benzene-1,4-dithiol, 1,4-benzenedimethanethiol, and dimercaptostilbene. Oligomer yields depend strongly on the used dithiol and on the dithiol-to-nanocluster ratio. Detailed analysis of the reaction yields in combination with simulations suggests that the system reaches a dynamic equilibrium, where ligand exchange happens continuously forming and breaking nanocluster oligomers that are bound together by short chains of disulfide-bridged dithiols. Despite the dynamic nature of the system, dithiol-induced polymerization of nanoclusters is a general and straightforward approach to produce dimers and larger oligomers of thiol-protected nanoclusters. Our work provides physical insight into, offers tools for, and reveals challenges in the controlled synthesis of covalently bound nanoparticle assemblies.

The effect of repeated-intermittent exposure to 5-methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) during adolescence on learning and memory in adult rats.

BACKGROUND: According to the European Drug Report, the use of novel psychoactive substances (NPS) is constantly growing. NPS are widely abused by human adolescent subjects. 5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is one of the most frequently used hallucinogenic NPS. 5-MeO-DIPT intoxication results in hallucinations, vomiting, and tachycardia. Long-term exposure to 5-MeO-DIPT was reported to lead to development of post-hallucinogenic perception disorder. The aim of the present study was to determine whether repeated-intermittent administration of 5-MeO-DIPT during adolescence affects learning and memory in adult rats. METHODS: Rats were treated with 5-MeO-DIPT in a dose of 2.5mg/kg from 30 to 33 and 37 to 40 Postnatal Day (PND). The experiments were conducted when the animals reached 90 PND. The effect of 5-MeO-DIPT on cognitive functions was assessed using the novel object recognition, open field, and serial pattern learning (SPL) tests. RESULTS: Repeated-intermittent exposure to 5-MeO-DIPT during adolescence decreased the number of crossings in the open field test at adulthood. Moreover, 5-MeO-DIPT treatment impaired adult rats' learning in the SPL test. There was no change in the novel object recognition test. CONCLUSIONS: The present results show that the performance of adult rats treated with 5-MeO-DIPT during adolescence was impaired in the open field test, which indicates the attenuated exploratory activity. 5-MeO-DIPT treatment undermined adult rats' performance in the serial pattern learning test, suggesting impairment of long term memory and cognitive flexibility. The present study showed that the exposure to 5-MeO-DIPT during adolescence might lead to long-lasting behavioral changes which persisted long after the exposure period.

Using rodents to model abnormal sensitivity to feedback in depression.

Depressive disorder accounts for a substantial proportion of psychiatric problems across the globe and has a devastating impact on quality of life and occupational function. Psychological models of depression emphasize the causal role of cognitive distortions in this disease, and cognitive problems have been included in the diagnostic criteria for depressive episodes. Here, we focus on recent progress in preclinical modelling of aberrations in one of the most important neurocognitive mechanisms involved in the manifestation of depression - abnormal sensitivity to positive and negative feedback. First, we summarize the recent advances in understanding neurocognitive mechanisms of aberrant feedback sensitivity in depression and underlying neurobiological substrates. Second, by combining behavioural, neurochemical, neuroanatomical and pharmacological approaches, we evaluate the translational value of the probabilistic reversal-learning (PRL) task, a behavioural paradigm that enables investigation of correlates of feedback sensitivity in humans and animals. Finally, we identify and discuss directions for future investigation, including cognitive biomarkers of depression and resilience to stress based on feedback sensitivity and personalized treatment targets.

The effect of chronic co-treatment with risperidone and novel antidepressant drugs on the dopamine and serotonin levels in the rats frontal cortex.

BACKGROUND: Preclinical and clinical studies have suggested a beneficial effect of combination treatment with atypical antipsychotic drugs and antidepressants (ADs) in schizophrenia and in drug-resistant depression. METHODS: In the present study, we investigated the effect of chronic administration of risperidone and ADs (escitalopram or mirtazapine), given separately or jointly on the extracellular levels of dopamine (DA) and serotonin (5-HT) in the rat frontal cortex. The animals were administered risperidone (0.2mg/kg) and escitalopram (5mg/kg) or mirtazapine (10mg/kg) repeatedly for 14days. The release of monoamines in the rat frontal cortex was evaluated using a microdialysis, and DA and 5-HT levels were assayed by HPLC. We also measured the locomotor activity, catalepsy and recognition memory in these rats. RESULTS: Chronic risperidone treatment (0.2mg/kg) increased the extracellular levels of DA and 5-HT. Co-treatment with risperidone and escitalopram (5mg/kg) or mirtazapine (10mg/kg) more efficiently increased the release of 5-HT but not DA in the rat frontal cortex, as compared to drugs given alone. Moreover, risperidone, escitalopram and mirtazapine given alone or in combination significantly decreased the locomotor activity and only mirtazapine increased the catalepsy evoked by risperidone. Combined treatment with risperidone and ADs impaired recognition memory in these rats. CONCLUSIONS: The obtained results suggest that chronic co-administration of risperidone and escitalopram or mirtazapine more efficiently increased 5-HT release in the rat frontal cortex as compared to drugs given alone and suggest that this effect may be of importance to the pharmacotherapy of schizophrenia and drug-resistant depression.

The Effects of Exposure to Mephedrone During Adolescence on Brain Neurotransmission and Neurotoxicity in Adult Rats.

According to the European Drug Report (2016), the use of synthetic cathinones, such as mephedrone, among young people has rapidly increased in the last years. Studies in humans indicate that psychostimulant drug use in adolescence increases risk of drug abuse in adulthood. Mephedrone by its interaction with transporters for dopamine (DAT) and serotonin (SERT) stimulates their release to the synaptic cleft. In animal studies, high repeated doses of mephedrone given to adolescent but not adult mice or rats induced toxic changes in 5-hydroxytryptamine (5-HT) neurons. The aim of our study was to investigate the effects of mephedrone given in adolescence on brain neurotransmission and possible neuronal injury in adult rats. Adolescent male rats were given mephedrone (5 mg/kg) for 8 days. In vivo microdialysis in adult rats showed an increase in dopamine (DA), 5-HT, and glutamate release in the nucleus accumbens and frontal cortex but not in the striatum in response to challenge dose in animals pretreated with mephedrone in adolescence. The 5-HT and 5-hydroxyindoleacetic acid contents decreased in the striatum and nucleus accumbens while DA turnover rates were decreased in the striatum and nucleus accumbens. The oxidative damage of DNA assessed with the alkaline comet assay was found in the cortex of adult rats. Therefore, the administration of repeated low doses of mephedrone during adolescence does not seem to induce injury to 5-HT and DA neurons. The oxidative stress seems to be responsible for possible damage of cortical cell bodies which causes maladaptive changes in serotonergic and dopaminergic neurons.

Risperidone and escitalopram co-administration: A potential treatment of schizophrenia symptoms with less side effects.

BACKGROUND: Schizophrenia is a psychiatric disorder characterized by positive and negative symptoms often accompanied by depression and cognitive deficits. Positive symptoms, like delusions and hallucinations are caused by an excess of dopamine (DA) signaling and are treated with the second generation antipsychotic drugs. Negative symptoms of schizophrenia are represented by social withdrawal, apathy and blunted emotional response. It was demonstrated that co-administration of risperidone and selective serotonin reuptake inhibitors alleviated depressive symptoms and cognitive dysfunction in animal models of schizophrenia. Moreover, combination of fluoxetine or mirtazapine with risperidone increased DA and 5-hydroxytryptamine (5-HT) release in the rat frontal cortex more potently than either drug given separately. The present study aimed to investigate whether combination of risperidone and escitalopram is effective in increasing DA and 5-HT release. METHODS: The extracellular level of neurotransmitters in the rat frontal cortex and nucleus accumbens was examined using microdialysis in freely moving animals. The dialysate concentration of DA and 5-HT was assayed by HPLC. RESULTS: It was found that risperidone (0.2 and 1mg/kg) and escitalopram (5 and 10mg/kg) given together significantly increased cortical DA and 5-HT levels and were more efficient in enhancing neurotransmitter concentrations than any single-drug treatment. A similar effect on DA and 5-HT release was observed in the nucleus accumbens after administration of risperidone (1mg/kg) and escitalopram (5mg/kg). CONCLUSIONS: The present study demonstrates that co-administration of risperidone and escitalopram may be used to treat positive and negative symptoms of schizophrenia and will allow to minimize the drugs' side effects.

Neurochemical and behavioral studies on the 5-HT1A-dependent antipsychotic action of the mGlu4 receptor agonist LSP4-2022.

LSP4-2022 is a novel, orthosteric agonist of mGlu4 receptor that induces antipsychotic-like activity in animal studies. In the present study, the involvement of 5-HT1A receptors in LSP4-2022-induced antipsychotic actions and the neurochemical background of that interaction were investigated. In several behavioral tests the actions of effective doses of the compound (0.5-2 mg/kg) were antagonized via the administration of the 5-HT1A antagonist WAY100635 (0.1 mg/kg). The co-administration of sub-effective dose of the 5-HT1A agonist (R)-(S)-8-OH-DPAT (0.01 mg/kg) intensified the activity of ineffective doses of LSP4-2022, having no influence on the efficacy of the active doses. The co-administration of effective doses of both compounds did not intensify each other's action. In the microdialysis in vivo tests, MK-801 (0.6 mg/kg) induced an enhancement of the release of dopamine, serotonin, glutamate and GABA in the prefrontal cortex. Administration of LSP4-2022 (2 mg/kg) abolished this MK-801-induced effect on neurotransmitter release. Co-administration with WAY100635 (0.1 mg/kg), a 5-HT1A antagonist, completely (dopamine, serotonin) or partially (glutamate, GABA) counteracted this LSP4-2022-induced effect. Subsequently, the patch-clamp recordings of spontaneous EPSCs were performed. sEPSCs were evoked in slices from the mouse prefrontal cortex by DOI (10 µM). LSP4-2022 (2.5; 5 and 10 µm) reversed DOI-induced changes in both the frequency and amplitude of the sEPSCs, but the more robust effect on the frequency was observed. The administration of WAY100635 had no effect on the LSP4-2022-induced effects on sEPSCs, indicating that the mGlu4-5-HT1A interaction does not occur via single-neuron signaling but involves neuronal circuits that regulate neurotransmitter release. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.

Neurotoxic Effects of 5-MeO-DIPT: A Psychoactive Tryptamine Derivative in Rats.

5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT, 'foxy') is one of the most popular tryptamine hallucinogens in the illicit drug market. It produces serious adverse effects, but its pharmacological profile is not well recognized. In vitro data have shown that 5-MeO-DIPT acts as a potent serotonin transporter (SERT) inhibitor and displays high affinity at serotonin 5-HT1A, 5-HT2A, and 5-HT2C receptors. In this study, using microdialysis in freely moving rats, we examined the effect of 5-MeO-DIPT on dopamine (DA), serotonin (5-HT), and glutamate release in the rat striatum, nucleus accumbens, and frontal cortex. In search of a possible neurotoxic effect of 5-MeO-DIPT, we measured DA and 5-HT tissue content in the above rat brain regions and also determined the oxidative DNA damage with the comet assay. Moreover, we tested drug-elicited head-twitch response and a forepaw treading induced by 8-OH-DPAT. 5-MeO-DIPT at doses of 5, 10, and 20 mg/kg increased extracellular DA, 5-HT, and glutamate level but the differences in the potency were found between brain regions. 5-MeO-DIPT increased 5-HT and decreased 5-HIAA tissue content which seems to result from SERT inhibition. On the other hand, a decrease in DA, DOPAC, and HVA tissue contents suggests possible adaptive changes in DA turnover or damage of DA terminals by 5-MeO-DIPT. DNA single and double-strand breaks persisted up to 60 days after the treatment, indicating marked neurotoxicity of 5-MeO-DIPT. The induction of head-twitch response and potentiation of forepaw treading induced by 8-OH-DPAT indicate that hallucinogenic activity seems to be mediated through the stimulation of 5-HT2A and 5-HT1A receptors by 5-MeO-DIPT.

Effect of Some Psychoactive Drugs Used as 'Legal Highs' on Brain Neurotransmitters.

New psychoactive "designer drugs" are synthetic compounds developed to provide similar effects to illicit drugs of abuse, but not subjected to legal control. The rapidly changing legal status of novel psychoactive drugs triggers the development of new compounds, analogs of well-known amphetamine or mescaline. New designer drugs used as substitutes in ecstasy pills are the least investigated and can cause life-threatening effects on users. The aim of our research was to examine the effects of acute administration of 4-methoxyamphetamine (PMA, 5 and 10 mg/kg), 4-methoxy-N-methylamphetamine (PMMA, 5 and 10 mg/kg), and mephedrone (MEPH, 5, 10 and 20 mg/kg) on extracellular and tissue level of dopamine (DA), 5-hydroxytryptamine (5-HT) and their metabolites in rat brain, by microdialysis method in freely moving animals and HPLC. Similarly to 3,4-methylenedioxymethamphetamine (MDMA, 5 and 10 mg/kg) PMA, PMMA and MEPH enhanced the release of DA and 5-HT in rat striatum, nucleus accumbens, and frontal cortex. DA tissue content was increased by MEPH and PMMA in striatum, by MEPH, PMA, and PMMA in nucleus accumbens, and by PMA in frontal cortex. Instead, cortical DA level was decreased by MEPH and PMMA. MEPH did not influence 5-HT tissue level in striatum and nucleus accumbens, but decreased its level in frontal cortex. PMMA increased 5-HT content in striatum, while PMA enhanced it in nucleus accumbens and frontal cortex. Observed changes in brain monoamines and their metabolites by new psychoactive drugs suggest that these drugs may be capable of development of dependence. Further experiments are needed to fully investigate the neurotoxic and abuse potential of those drugs.

Covalently linked multimers of gold nanoclusters Au102(p-MBA)44 and Au∼250(p-MBA)n.

We present the synthesis, separation, and characterization of covalently-bound multimers of para-mercaptobenzoic acid (p-MBA) protected gold nanoclusters. The multimers were synthesized by performing a ligand-exchange reaction of a pre-characterized Au102(p-MBA)44 nanocluster with biphenyl-4,4'-dithiol (BPDT). The reaction products were separated using gel electrophoresis yielding several distinct bands. The bands were analyzed by transmission electron microscopy (TEM) revealing monomer, dimer, and trimer fractions of the nanocluster. TEM analysis of dimers in combination with molecular dynamics simulations suggest that the nanoclusters are covalently bound via a disulfide bridge between BPDT molecules. The linking chemistry is not specific to Au102(p-MBA)44. The same approach yields multimers also for a larger monodisperse p-MBA-protected cluster of approximately 250 gold atoms, Au∼250(p-MBA)n. While the Au102(p-MBA)44 is not plasmonic, the Au∼250(p-MBA)n nanocluster supports localized surface plasmon resonance (LSPR) at 530 nm. Multimers of the Au∼250(p-MBA)n exhibit additional transitions in their UV-vis spectrum at 630 nm and 810 nm, indicating the presence of hybridized LSPR modes. Well-defined structures and relatively small sizes make these systems excellent candidates for connecting ab initio theoretical studies and experimental quantum plasmonics. Moreover, our work opens new possibilities in the controlled synthesis of advanced monodisperse nanocluster superstructures.

Alterations of Bio-elements, Oxidative, and Inflammatory Status in the Zinc Deficiency Model in Rats.

Our previous study showed that dietary zinc restriction induces depression-like behavior with concomitant up-regulation of the N-methyl-D-aspartate receptor (NMDAR). Because metal ions, oxidative stress, and inflammation are involved in depression/NMDAR function, in the present study, bio-elements (zinc, copper, iron, magnesium, and calcium), oxidative (thiobarbituric acid-reactive substances; protein carbonyl content), and inflammatory (IL-1α, IL-1ß) factors were measured in serum, hippocampus (Hp), and prefrontal cortex (PFC) of male Sprague-Dawley rats subjected to a zinc-adequate (ZnA) (50 mg Zn/kg) or a zinc-deficient (ZnD) (3 mg Zn/kg) diet for 4 or 6 weeks. Both periods of dietary zinc restriction reduced serum zinc and increased serum iron levels. At 4 weeks, lowered zinc level in the PFC and Hp as well as lowered iron level in the PFC of the ZnD rats was observed. At 6 weeks, however, iron level was increased in the PFC of these rats. Although at 6 weeks zinc level in the PFC did not differ between the ZnA and ZnD rats, extracellular zinc concentration after 100 mM KCl stimulation was reduced in the PFC of the ZnD rats and was accompanied by increased extracellular iron and glutamate levels (as measured by the in vivo microdialysis). The examined oxidative and inflammatory parameters were generally enhanced in the tissue of the ZnD animals. The obtained data suggest dynamic redistribution of bio-elements and enhancement of oxidative/inflammatory parameters after dietary zinc restriction, which may have a link with depression-like behavior/NMDAR function/neurodegeneration.

The antipsychotic-like effects in rodents of the positive allosteric modulator Lu AF21934 involve 5-HT1A receptor signaling: mechanistic studies.

RATIONALE: Diverse preclinical studies suggest the potential therapeutic utility of the modulation of the glutamatergic system in brain via metabotropic glutamate (mGlu) receptors. Lu AF21934, a positive allosteric modulator of the mGlu4 receptor, was previously shown to reverse behavioral phenotypes in animal models thought to mimic positive, negative, and cognitive symptoms of schizophrenia. OBJECTIVES: To begin elucidating the brain circuitry involved in mGlu4 receptor pharmacology and add mechanistic support to Lu AF21934-induced phenotypic responses, the potential involvement of 5-HT1A receptors in these antipsychotic-like effects was explored. The tests used were the following: MK-801-induced hyperactivity and 2,5-dimethoxy-4-iodoamphetamine (DOI)-induced head twitches in mice, for positive symptoms; MK-801-induced disruptions of social interactions for negative symptoms; and novel object recognition and spatial delayed alteration test for cognitive symptoms. The microdialysis studies in which the effect of Lu AF21934 on MK-801-induced dopamine and serotonin release was investigated. RESULTS: The effects caused by Lu AF2193 were inhibited by administration of the selective 5-HT1A receptor antagonist WAY100635 (0.1 mg/kg). That inhibition was observed across all models used. Moreover, the concomitant administration of sub-effective doses of Lu AF21934 and a sub-effective dose of the selective 5-HT1A receptor agonist tool compound (R)-(+)-8-hydroxy-DPAT hydrobromide (0.01 mg/kg) induced a clear antipsychotic-like effect in all the procedures used. Lu AF21934 (5 mg/kg) also inhibited MK-801-induced increase in dopamine and 5-HT release. CONCLUSIONS: The actions of Lu AF21934 are 5-HT1A receptor-dependent. Activation of the mGlu4 receptor may be a promising mechanism for the development of novel antipsychotic drugs, efficacious toward positive, negative, and cognitive symptoms.