Chirality Matters: Fine-Tuning of Novel Monoamine Reuptake Inhibitors Selectivity through Manipulation of Stereochemistry.

The high structural similarity, especially in transmembrane regions, of dopamine, norepinephrine, and serotonin transporters, as well as the lack of all crystal structures of human isoforms, make the specific targeting of individual transporters rather challenging. Ligand design itself is also rather limited, as many chemists, fully aware of the synthetic and analytical challenges, tend to modify lead compounds in a way that reduces the number of chiral centers and hence limits the potential chemical space of synthetic ligands. We have previously shown that increasing molecular complexity by introducing additional chiral centers ultimately leads to more selective and potent dopamine reuptake inhibitors. Herein, we significantly extend our structure-activity relationship of dopamine transporter-selective ligands and further demonstrate how stereoisomers of defined absolute configuration may fine-tune and direct the activity towards distinct targets. From the pool of active compounds, using the examples of stereoisomers 7h and 8h, we further showcase how in vitro activity significantly differs in in vivo drug efficacy experiments, calling for proper validation of individual stereoisomers in animal studies. Furthermore, by generating a large library of compounds with defined absolute configurations, we lay the groundwork for computational chemists to further optimize and rationally design specific monoamine transporter reuptake inhibitors.

Low-Affinity/High-Selectivity Dopamine Transport Inhibition Sufficient to Rescue Cognitive Functions in the Aging Rat.

The worldwide increase in cognitive decline, both in aging and with psychiatric disorders, warrants a search for pharmacological treatment. Although dopaminergic treatment approaches represent a major step forward, current dopamine transporter (DAT) inhibitors are not sufficiently specific as they also target other transporters and receptors, thus showing unwanted side effects. Herein, we describe an enantiomerically pure, highly specific DAT inhibitor, S-CE-123, synthetized in our laboratory. Following binding studies to DAT, NET and SERT, GPCR and kinome screening, pharmacokinetics and a basic neurotoxic screen, S-CE-123 was tested for its potential to enhance and/or rescue cognitive functions in young and in aged rats in the non-invasive reward-motivated paradigm of a hole-board test for spatial learning. In addition, an open field study with young rats was carried out. We demonstrated that S-CE-123 is a low-affinity but highly selective dopamine reuptake inhibitor with good bioavailability. S-CE-123 did not induce hyperlocomotion or anxiogenic or stereotypic behaviour in young rats. Our compound improved the performance of aged but not young rats in a reward-motivated task. The well-described impairment of the dopaminergic system in aging may underlie the age-specific effect. We propose S-CE-123 as a possible candidate for developing a tentative therapeutic strategy for age-related cognitive decline and cognitive dysfunction in psychiatric disorders.

Novel Dopamine Transporter Inhibitor, CE-123, Ameliorates Spatial Memory Deficits Induced by Maternal Separation in Adolescent Rats: Impact of Sex.

Maternal separation (MS) is a key contributor to neurodevelopmental disorders, including learning disabilities. To test the hypothesis that dopamine signaling is a major factor in this, an atypical new dopamine transporter (DAT) inhibitor, CE-123, was assessed for its potential to counteract the MS-induced spatial learning and memory deficit in male and female rats. Hence, neonatal rats (postnatal day (PND)1 to 21) were exposed to MS (180 min/day). Next, the acquisition of spatial learning and memory (Barnes maze task) and the expression of dopamine D1 receptor, dopamine transporter (DAT), and the neuronal GTPase, RIT2, which binds DAT in the vehicle-treated rats were evaluated in the prefrontal cortex and hippocampus in the adolescent animals. The results show that MS impairs the acquisition of spatial learning and memory in rats, with a more severe effect in females. Moreover, the MS induced upregulation of DAT and dopamine D1 receptors expression in the prefrontal cortex and hippocampus in adolescent rats. Regarding RIT2, the expression was decreased in the hippocampus for both the males and females, however, in the prefrontal cortex, reduction was found only in the females, suggesting that there are region-specific differences in DAT endocytic trafficking. CE-123 ameliorated the behavioral deficits associated with MS. Furthermore, it decreased the MS-induced upregulation of D1 receptor expression level in the hippocampus. These effects were more noted in females. Overall, CE-123, an atypical DAT inhibitor, is able to restore cognitive impairment and dopamine signaling in adolescent rats exposed to MS-with more evident effect in females than males.

A Novel and Selective Dopamine Transporter Inhibitor, (S)-MK-26, Promotes Hippocampal Synaptic Plasticity and Restores Effort-Related Motivational Dysfunctions.

Dopamine (DA), the most abundant human brain catecholaminergic neurotransmitter, modulates key behavioral and neurological processes in young and senescent brains, including motricity, sleep, attention, emotion, learning and memory, and social and reward-seeking behaviors. The DA transporter (DAT) regulates transsynaptic DA levels, influencing all these processes. Compounds targeting DAT (e.g., cocaine and amphetamines) were historically used to shape mood and cognition, but these substances typically lead to severe negative side effects (tolerance, abuse, addiction, and dependence). DA/DAT signaling dysfunctions are associated with neuropsychiatric and progressive brain disorders, including Parkinson's and Alzheimer diseases, drug addiction and dementia, resulting in devastating personal and familial concerns and high socioeconomic costs worldwide. The development of low-side-effect, new/selective medicaments with reduced abuse-liability and which ameliorate DA/DAT-related dysfunctions is therefore crucial in the fields of medicine and healthcare. Using the rat as experimental animal model, the present work describes the synthesis and pharmacological profile of (S)-MK-26, a new modafinil analogue with markedly improved potency and selectivity for DAT over parent drug. Ex vivo electrophysiology revealed significantly augmented hippocampal long-term synaptic potentiation upon acute, intraperitoneally delivered (S)-MK-26 treatment, whereas in vivo experiments in the hole-board test showed only lesser effects on reference memory performance in aged rats. However, in effort-related FR5/chow and PROG/chow feeding choice experiments, (S)-MK-26 treatment reversed the depression-like behavior induced by the dopamine-depleting drug tetrabenazine (TBZ) and increased the selection of high-effort alternatives. Moreover, in in vivo microdialysis experiments, (S)-MK-26 significantly increased extracellular DA levels in the prefrontal cortex and in nucleus accumbens core and shell. These studies highlight (S)-MK-26 as a potent enhancer of transsynaptic DA and promoter of synaptic plasticity, with predominant beneficial effects on effort-related behaviors, thus proposing therapeutic potentials for (S)-MK-26 in the treatment of low-effort exertion and motivational dysfunctions characteristic of depression and aging-related disorders.

The Novel Analogue of Modafinil CE-158 Protects Social Memory against Interference and Triggers the Release of Dopamine in the Nucleus Accumbens of Mice.

Previous studies have shown that atypical dopamine-transporter-inhibitors such as modafinil and its analogues modify behavioral and cognitive functions in rodents. Here, we tested potential promnestic effects of the novel, more dopamine-transporter selective modafinil analogue CE-158 in the social discrimination memory task in male mice. Systemic administration of CE-158 1 h before the social learning event prevented the impairment of social-recognition memory following retroactive interference 3 h after the learning session of a juvenile conspecific. This effect was dose-dependent, as mice treated with 10 mg/kg, but not with 1 mg/kg CE-158, were able to discriminate between the novel and familiar conspecific despite the presentation of an interference stimulus, both 3 h and 6 h post learning. However, when 10 mg/kg of the drug was administered after learning, CE-158 failed to prevent social memory from interference. Paralleling these behavioral effects, the systemic administration of 10 mg/kg CE-158 caused a rapid and sustained elevation of extracellular dopamine in the nucleus accumbens, a brain area where dopaminergic signaling plays a key role in learning and memory function, of freely moving mice, while 1 mg/kg was not sufficient for altering dopamine levels. Taken together, our findings suggest promnestic effects of the novel dopamine-transporter-inhibitor CE-158 in a social recognition memory test that may be in part mediated via increased dopamine-neurotransmission in the nucleus accumbens. Thus, selective-dopamine-transporter-inhibitors such as CE-158 may represent interesting drug candidates for the treatment of memory complaints observed in humans with cognitive impairments and dementia.

Synthesis and dopamine receptor binding of dihydrexidine and SKF 38393 catecholamine-based analogues.

Dopamine is an important neurotransmitter that regulates numerous essential functions, including cognition and voluntary movement. As such, it serves as an important scaffold for synthesis of novel analogues as part of drug development effort to obtain drugs for treatment of neurodegenerative diseases, such as Parkinson's disease. To that end, similarity search of the ZINC database based on two known dopamine-1 receptor (D1R) agonists, dihydrexidine (DHX) and SKF 38393, respectively, was used to predict novel chemical entities with potential binding to D1R. Three compounds that showed the highest similarity index were selected for synthesis and bioactivity profiling. All main synthesis products as well as the isolated intermediates, were properly characterized. The physico-chemical analyses were performed using HRESIMS, GC/MS, LC/MS with UV-Vis detection, and FTIR, 1H NMR and 13C NMR spectroscopy. Binding to D1 and D2 receptors and inhibition of dopamine reuptake via dopamine transporter were measured for the synthesized analogues of DHX and SKF 38393.

Reinstatement of synaptic plasticity in the aging brain through specific dopamine transporter inhibition.

Aging-related neurological deficits negatively impact mental health, productivity, and social interactions leading to a pronounced socioeconomic burden. Since declining brain dopamine signaling during aging is associated with the onset of neurological impairments, we produced a selective dopamine transporter (DAT) inhibitor to restore endogenous dopamine levels and improve cognitive function. We describe the synthesis and pharmacological profile of (S,S)-CE-158, a highly specific DAT inhibitor, which increases dopamine levels in brain regions associated with cognition. We find both a potentiation of neurotransmission and coincident restoration of dendritic spines in the dorsal hippocampus, indicative of reinstatement of dopamine-induced synaptic plasticity in aging rodents. Treatment with (S,S)-CE-158 significantly improved behavioral flexibility in scopolamine-compromised animals and increased the number of spontaneously active prefrontal cortical neurons, both in young and aging rodents. In addition, (S,S)-CE-158 restored learning and memory recall in aging rats comparable to their young performance in a hippocampus-dependent hole board test. In sum, we present a well-tolerated, highly selective DAT inhibitor that normalizes the age-related decline in cognitive function at a synaptic level through increased dopamine signaling.

CE-123, a novel dopamine transporter inhibitor, attenuates locomotor hyperactivity and improves cognitive functions in rat model of fetal alcohol spectrum disorders.

Perinatal alcohol exposure can lead to fetal alcohol spectrum disorders (FASD), usually first diagnosed in childhood, that are characterized by hyperactivity, impulsivity and learning and memory disability, among others. To test the hypothesis that dopamine signaling is one of the main factors underlying these impairments, a new atypical dopamine transporter (DAT) inhibitor, CE-123 (1, 3 or 10 mg/kg) was assessed for its potential to overcome the ethanol-induced behavioral effects in a rat model of FASD. In the present study, neonatal rats were exposed to alcohol intubations across the neonatal period (postnatal day (PND)4-9, the third trimester equivalent of human gestation) and, after weaning, the animals (male rats) were assigned randomly to three groups. The first group was tested at PND21 (hyperactivity test). A second group was tested at PND45 (anxiety test), at PND47 (locomotor activity test), at PND49 (spatial cognitive test in the Barnes maze) and PND50 (reversal learning in the Barnes maze). The third group was tested at PND50 (dopamine receptor mRNA expression). Our results support the hypothesis that dopamine signaling is associated with FASD because the dopamine (D1, D2 and D5) receptor mRNA expression was altered in the striatum, hippocampus and prefrontal cortex in adult rats exposed to ethanol during neonatal period. CE-123 (3 and 10 mg/kg) inhibited the hyperactivity and ameliorated (10 mg/kg) the impairment of reversal learning in alcohol-exposed rats. Thus, these findings provide support that CE-123 may be a useful intervention for same of the deficits associated with neonatal ethanol exposure.

Behavioral and dopamine transporter binding properties of the modafinil analog (S, S)-CE-158: reversal of the motivational effects of tetrabenazine and enhancement of progressive ratio responding.

RATIONALE: Atypical dopamine (DA) transport blockers such as modafinil and its analogs may be useful for treating motivational symptoms of depression and other disorders. Previous research has shown that the DA depleting agent tetrabenazine can reliably induce motivational deficits in rats, as evidenced by a shift towards a low-effort bias in effort-based choice tasks. This is consistent with human studies showing that people with major depression show a bias towards low-effort activities. OBJECTIVES: Recent studies demonstrated that the atypical DA transport (DAT) inhibitor (S)-CE-123 reversed tetrabenazine-induced motivational deficits, increased progressive ratio (PROG) lever pressing, and increased extracellular DA in the nucleus accumbens. In the present studies, a recently synthesized modafinil analog, (S, S)-CE-158, was assessed in a series of neurochemical and behavioral studies in rats. RESULTS: (S, S)-CE-158 demonstrated the ability to reverse the effort-related effects of tetrabenazine and increase selection of high-effort PROG lever pressing in rats tested on PROG/chow feeding choice task. (S, S)-CE-158 showed a high selectivity for inhibiting DAT compared with other monoamine transporters, and systemic administration of (S, S)-CE-158 increased extracellular DA in the nucleus accumbens during the behaviorally active time course, which is consistent with the effects of (S)-CE-123 and other DAT inhibitors that enhance high-effort responding. CONCLUSIONS: These studies provide an initial neurochemical characterization of a novel atypical DAT inhibitor, and demonstrate that this compound is active in models of effort-related choice. This research could contribute to the development of novel compounds for the treatment of motivational dysfunctions in humans.

Neurophysiological and Neurochemical Effects of the Putative Cognitive Enhancer (S)-CE-123 on Mesocorticolimbic Dopamine System.

Treatments for cognitive impairments associated with neuropsychiatric disorders, such as attention deficit hyperactivity disorder or narcolepsy, aim at modulating extracellular dopamine levels in the brain. CE-123 (5-((benzhydrylsulfinyl)methyl) thiazole) is a novel modafinil analog with improved specificity and efficacy for dopamine transporter inhibition that improves cognitive and motivational processes in experimental animals. We studied the neuropharmacological and behavioral effects of the S-enantiomer of CE-123 ((S)-CE-123) and R-modafinil in cognitive- and reward-related brain areas of adult male rats. In vivo single unit recordings in anesthetized animals showed that (S)-CE-123, but not R-modafinil, dose-dependently (1.25 to 10 mg/kg i.v.) reduced firing of pyramidal neurons in the infralimbic/prelimbic (IL/PrL) cortex. Neither compound the affected firing activity of ventral tegmental area dopamine cells. In freely moving animals, (S)-CE-123 (10 mg/kg i.p.) increased extracellular dopamine levels in the IL/PrL, with different patterns when compared to R-modafinil (10 mg/kg i.p.); in the nucleus accumbens shell, a low and transitory increase of dopamine was observed only after (S)-CE-123. Neither (S)-CE-123 nor R-modafinil initiated the emission of 50-kHz ultrasonic vocalizations, a behavioral marker of positive affect and drug-mediated reward. Our data support previous reports of the procognitive effects of (S)-CE-123, and show a minor impact on reward-related dopaminergic areas.

Structure-Activity Relationships of Novel Thiazole-Based Modafinil Analogues Acting at Monoamine Transporters.

Atypical dopamine reuptake inhibitors, such as modafinil, are used for the treatment of sleeping disorders and investigated as potential therapeutics against cocaine addiction and for cognitive enhancement. Our continuous effort to find modafinil analogues with higher inhibitory activity on and selectivity toward the dopamine transporter (DAT) has previously led to the promising thiazole-containing derivatives CE-103, CE-111, CE-123, and CE-125. Here, we describe the synthesis and activity of a series of compounds based on these scaffolds, which resulted in several new selective DAT inhibitors and gave valuable insights into the structure-activity relationships. Introduction of the second chiral center and subsequent chiral separations provided all four stereoisomers, whereby the S-configuration on both generally exerted the highest activity and selectivity on DAT. The representative compound of this series was further characterized by in silico, in vitro, and in vivo studies that have demonstrated both safety and efficacy profile of this compound class.

The Novel Atypical Dopamine Uptake Inhibitor (S)-CE-123 Partially Reverses the Effort-Related Effects of the Dopamine Depleting Agent Tetrabenazine and Increases Progressive Ratio Responding.

Animal studies of effort-based choice behavior are being used to model effort-related motivational dysfunctions in humans. With these procedures, animals are offered a choice between high-effort instrumental actions leading to highly valued reinforcers vs. low effort/low reward options. Several previous studies have shown that dopamine (DA) uptake inhibitors, including GBR12909, lisdexamfetamine, methylphenidate, and PRX-14040, can reverse the effort-related effects of the vesicular monoamine transport blocker tetrabenazine, which inhibits DA storage. Because many drugs that block DA transport act as major stimulants that also release DA, and produce a number of undesirable side effects, there is a need to develop and characterize novel atypical DA transport inhibitors. (S)-CE-123 ((S)-5-((benzhydrylsulfinyl) methyl)thiazole) is a recently developed analog of modafinil with the biochemical characteristics of an atypical DA transport blocker. The present paper describes the enantioselective synthesis and initial chemical characterization of (S)-CE-123, as well as behavioral experiments involving effort-based choice and microdialysis studies of extracellular DA. Rats were assessed using the fixed ratio 5/chow feeding choice test. Tetrabenazine (1.0 mg/kg) shifted choice behavior, decreasing lever pressing and increasing chow intake. (S)-CE-123 was coadministered at doses ranging from 6.0 to 24.0 mg/kg, and the highest dose partially but significantly reversed the effects of tetrabenazine, although this dose had no effect on fixed ratio responding when administered alone. Additional experiments showed that (S)-CE-123 significantly increased lever pressing on a progressive ratio/chow feeding choice task and that the effective dose (24.0 mg/kg) increased extracellular DA in nucleus accumbens core. In summary, (S)-CE-123 has the behavioral and neurochemical profile of a compound that can block DA transport, reverse the effort-related effects of tetrabenazine, and increase selection of high-effort progressive ratio responding. This suggests that (S)-CE-123 or a similar compound could be useful as a treatment for effort-related motivational dysfunction in humans.

Differential Effects of Novel Dopamine Reuptake Inhibitors on Interference With Long-Term Social Memory in Mice.

In the laboratory, long-term social recognition memory (SRM) in mice is highly susceptible to proactive and retroactive interference. Here, we investigate the ability of novel designed dopamine (DA) re-uptake inhibitors (rac-CE-123 and S-CE-123) to block retroactive and proactive interference, respectively. Our data show that administration of rac-CE-123 30 min before learning blocks retroactive interference that has been experimentally induced at 3 h, but not at 6 h, post-learning. In contrast, S-CE-123 treatment 30 min before learning blocked the induction of retroactive interference at 6 h, but not 3 h, post-learning. Administration of S-CE-123 failed to interfere with proactive interference at both 3 h and 6 h. Analysis of additional behavioral parameters collected during the memory task implies that the effects of the new DA re-uptake inhibitors on retroactive and proactive interference cannot easily be explained by non-specific effects on the animals' general social behavior. Furthermore, we assessed the mechanisms of action of drugs using intracerebral in vivo-microdialysis technique. The results revealed that administration of rac-CE-123 and S-CE-123 dose-dependently increased DA release within the nucleus accumbens of freely behaving mice. Thus, the data from the present study suggests that the DA re-uptake inhibitors tested protect the consolidation of long-term social memory against interference for defined durations after learning. In addition, the data implies that DA signaling in distinct brain areas including the nucleus accumbens is involved in the consolidation of SRM in laboratory mice.

A daily single dose of a novel modafinil analogue CE-123 improves memory acquisition and memory retrieval.

Dopamine reuptake inhibitors have been shown to improve cognitive parameters in various tasks and animal models. We recently reported a series of modafinil analogues, of which the most promising, 5-((benzhydrylsulfinyl)methyl) thiazole (CE-123), was selected for further development. The present study aims to characterize pharmacological properties of CE-123 and to investigate the potential to enhance memory performance in a rat model. In vitro transporter assays were performed in cells expressing human transporters. CE-123 blocked uptake of [3H] dopamine (IC50 = 4.606 µM) while effects on serotonin (SERT) and the norepinephrine transporter (NET) were negligible. Blood-brain barrier and pharmacokinetic studies showed that the compound reached the brain and lower elimination than R-modafinil. The Pro-cognitive effect was evaluated in a spatial hole-board task in male Sprague-Dawley rats and CE-123 enhances memory acquisition and memory retrieval, represented by significantly increased reference memory indices and shortened latency. Since DAT blockers can be considered as indirect dopamine receptor agonists, western blotting was used to quantify protein levels of dopamine receptors D1R, D2R and D5R and DAT in the synaptosomal fraction of hippocampal subregions CA1, CA3 and dentate gyrus (DG). CE-123 administration in rats increased total DAT levels and D1R protein levels were significantly increased in CA1 and CA3 in treated/trained groups. The increase of D5R was observed in DG only. Dopamine receptors, particularly D1R, seem to play a role in mediating CE-123-induced memory enhancement. Dopamine reuptake inhibition by CE-123 may represent a novel and improved stimulant therapeutic for impairments of cognitive functions.

A Novel Dopamine Transporter Inhibitor CE-123 Improves Cognitive Flexibility and Maintains Impulsivity in Healthy Male Rats.

Reduced cognitive abilities are often characterized by an impairment of flexibility, i.e., the ability to switch from learned rules or categories that were important in certain contexts to different new modalities that rule the task. Drugs targeting the dopamine transporter (DAT) are widely used for their potential to enhance cognitive abilities. However, commercially available drugs are of limited specificity for DAT, blocking also noradrenaline and serotonine transporters, that can lead to unwanted side effects in healthy subjects. Therefore, we tested a newly synthetized compound (CE-123) with higher specificity for DAT in male rats in an attentional set-shifting task (ASST), that proves for cognitive flexibility and a 5-choice serial-reaction time task (5-CSRTT) assessing visuospatial attention and impulsivity. Treated rats at a dose of 0.3 and 1.0 but not 0.1 mg/kg bodyweight showed reduced extra-dimensional shifts in the ASST compared to controls indicating increased cognitive flexibility. Rats treated with R-Modafinil, a commercially available DAT inhibitor at a dose of 10 mg/kg bodyweight showed increased premature responses, an indicator of increased impulsivity, during a 10 s but not a 2.5, 5, or 7.5 s intertrial interval when compared to vehicle-treated rats in the 5-CSRTT. This was not found in rats treated with CE-123 at the same dose as for R-Modafinil. Visuospatial attention, except premature responses, did not differ between R-Modafinil and CE-123-treated rats and their respective controls. Thus, CE-123 increased cognitive flexibility with diminished impulsivity.

Heterocyclic Analogues of Modafinil as Novel, Atypical Dopamine Transporter Inhibitors.

Modafinil is a wake promoting compound with high potential for cognitive enhancement. It is targeting the dopamine transporter (DAT) with moderate selectivity, thereby leading to reuptake inhibition and increased dopamine levels in the synaptic cleft. A series of modafinil analogues have been reported so far, but more target-specific analogues remain to be discovered. It was the aim of this study to synthesize and characterize such analogues and, indeed, a series of compounds were showing higher activities on the DAT and a higher selectivity toward DAT versus serotonin and norepinephrine transporters than modafinil. This was achieved by substituting the amide moiety by five- and six-membered aromatic heterocycles. In vitro studies indicated binding to the cocaine pocket on DAT, although molecular dynamics revealed binding different from that of cocaine. Moreover, no release of dopamine was observed, ruling out amphetamine-like effects. The absence of neurotoxicity of a representative analogue may encourage further preclinical studies of the above-mentioned compounds.

R-Modafinil exerts weak effects on spatial memory acquisition and dentate gyrus synaptic plasticity.

Modafinil is a wake promoting drug approved for clinical use and also has cognitive enhancing properties. Its enantiomer R-Modafinil (R-MO) is not well studied in regard to cognitive enhancing properties. Hence we studied its effect in a spatial memory paradigm and its possible effects on dentate gyrus long-term potentiation (DG-LTP). Clinically relevant doses of R-MO, vehicle dimethyl sulfoxide (DMSO) or saline were administered for three days during the hole-board test and in in vivo DG-LTP. Synaptic levels of dopamine receptors D1R, D2R, dopamine transporter (DAT), and its phosphorylated form (ph-DAT) in DG tissue 4 h after LTP induction were quantified by western blot analysis. Monoamine reuptake and release assays were performed by using transfected HEK-293 cells. Possible neurotoxic side effects on general behaviour were also studied. R-MO at both doses significantly enhanced spatial reference memory during the last training session and during memory retrieval compared to DMSO vehicle but not when compared to saline treated rats. Similarly, R-MO rescues DG-LTP from impairing effects of DMSO. DMSO reduced memory performance and LTP magnitude when compared to saline treated groups. The synaptic DR1 levels in R-MO groups were significantly decreased compared to DMSO group but were comparable with saline treated animals. We found no effect of R-MO in neurotoxicity tests. Thus, our results support the notion that LTP-like synaptic plasticity processes could be one of the factors contributing to the cognitive enhancing effects of spatial memory traces. D1R may play an important regulatory role in these processes.

A novel heterocyclic compound improves working memory in the radial arm maze and modulates the dopamine receptor D1R in frontal cortex of the Sprague-Dawley rat.

A series of compounds have been shown to enhance cognitive function via the dopaminergic system and indeed the search for more active and less toxic compounds is continuing. It was therefore the aim of the study to synthetise and test a novel heterocyclic compound for cognitive enhancement in a paradigm for working memory. Specific and effective dopamine re-uptake inhibition DAT (IC50=4,1±0,8µM) made us test this compound in a radial arm maze (RAM) in the rat. CE-125 (4-((benzhydrylsulfinyl)methyl)-2-cyclopropylthiazole), was tested for dopamine (DAT), serotonin and norepinephrine re-uptake inhibition by a well-established system. The working memory index (WMI) was evaluated in male Sprague Dawley rats that were intraperitoneally injected with CE-125 (1 or 10mg/kg body weight). In order to evaluate basic neurotoxicity, the open field, elevated plus maze, rota rod studies and the forced swim test were carried out. Frontal cortex was taken at the last day of the RAM test and dopamine receptors D1R and D2R, DAT and phosphorylated DAT protein levels were determined. On the 10th day both doses were increasing the WMI as compared to the vehicle-treated group. In both, trained and treated groups, D1R levels were significantly reduced while D2R levels were unchanged. DAT levels were comparable between all groups while phosphorylated DAT levels were increased in the trained group treated with 1mg/kg body weight. CE-125 as a probably non-neurotoxic compound and specific reuptake inhibitor was shown to increase performance (WMI) and modulation of the dopaminergic system is proposed as a possible mechanism of action.

Design of biocompatible immobilized Candida rugosa lipase with potential application in food industry.

BACKGROUND: Biocatalysts are a promising alternative for the production of natural flavor compounds. Candida rugosa lipase (CRL) is a particularly important biocatalyst owing to its remarkable efficiency in both hydrolysis and synthesis. However, additional stabilization is necessary for successful industrial implementation. This study presents an easy and time-saving method for immobilizing this valuable enzyme on hydroxyapatite (HAP), a biomaterial with high protein-binding capacity. RESULTS: Targeted immobilized CRL was obtained in high yield of ≥98%. Significant lipase stabilization was observed upon immobilization: at 60 °C, immobilized lipase (HAP-CRL) retained almost unchanged activity after 3 h, while free CRL lost 50% of its initial activity after only 30 min. The same trend was observed with tested organic solvents. Methanol and hexane had the most pronounced effect: after 3 h, only HAP-CRL was stable and active, while CRL was completely inactivated. The practical value of the prepared catalyst was tested in the synthesis of the aroma ester methyl acetate in hexane. Reaction yields were 2.6 and 52.5% for CRL and HAP-CRL respectively. CONCLUSION: This research has successfully combined an industrially prominent biocatalyst, CRL, and a biocompatible, environmentally suitable carrier, HAP, into an immobilized preparation with improved catalytic properties. The obtained CRL preparation has excellent potential for the food and flavor industries, major consumers in the global enzyme market. © 2016 Society of Chemical Industry.