Elsebet Ø Nielsen

University of Copenhagen, Copenhagen, Capital Region, Denmark

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Publications (80)318.47 Total impact

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    ABSTRACT: Introduction Positron emission tomography (PET) imaging of the norepinephrine transporter (NET) is still hindered by the availability of useful PET imaging probes. The present study describes the radiosynthesis and pre-clinical evaluation of a new compound, exo-3-(6-methoxypyridin-2-yloxy)-8-H-8-azabicyclo[3.2.1]octane (NS8880), targeting NET. NS8880 has an in vitro binding profile comparable to desipramine and is structurally not related to reboxetine. Methods Labeling of NS8880 with [11C] was achieved by a non-conventional technique: substitution of pyridinyl fluorine with [11C]methanolate in a Boc-protected precursor. The isolated [11C]NS8880 was evaluated pre-clinically both in a pig model (PET scanning) and in a rat model (μPET scanning) and compared to (S,S)-[11C]-O-methylreboxetine ([11C]MeNER). Results The radiolabeling technique yielded [11C]NS8880 in low (< 10%) but still useful yields with high purity. The PET in vivo evaluation in pig and rat revealed a rapid brain uptake of [11C]NS8880 and fast obtaining of equilibrium. Highest binding was observed in thalamic and hypothalamic regions. Pretreatment with desipramine efficiently reduced binding of [11C]NS8880. Conclusion Based on the pre-clinical results obtained so far [11C]NS8880 displays promising properties for PET imaging of NET.
    Nuclear Medicine and Biology 10/2014; · 2.52 Impact Factor
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    ABSTRACT: As affective and cognitive disturbances frequently co-occur in psychiatric disorders, research into opportunities to simultaneously target both entities is warranted. These disorders are typically treated with monoamine reuptake inhibitors (MRIs), whereas ongoing research suggests that symptoms also improve by nicotinic acetylcholine receptor (nAChR) activation. Preclinical studies have corroborated this and also demonstrated a synergistic antidepressant-like action when nAChR agonists and MRIs are combined. Here, we present the in vitro and in vivo profile of NS9775, a combined full α7 nAChR agonist and triple MRI. NS9775 potently inhibited [(3)H]α-bungarotoxin binding in vitro (Ki: 1.8 nM), and ex vivo (ED50: 3.6 mg/kg), showing negligible activity at α4β2- (Ki: 1,720 nM) or α1-containing nAChRs (Ki: 12,200 nM). In α7-expressing oocytes, NS9775 displayed an EC50 value of 280 nM, with a maximal response of 77% relative to a saturating acetylcholine concentration. Furthermore, NS9775 inhibited cortical [(3)H]5-HT, [(3)H]NA and [(3)H]DA uptake equipotently (14-43 nM), and inhibited striatal [(3)H]WIN35,428 binding (ED50: 9.1 mg/kg). Behaviourally in mice, NS9775 (0.3-3.0 mg/kg) reversed scopolamine-induced deficits in a modified Y-maze and MK-801-induced learning deficits in 5-trial inhibitory avoidance. Swim distance in the forced swim test was increased by 30 mg/kg NS9775, and 10 and 30 mg/kg NS9775 reduced digging behaviour in the marble burying paradigm and increased the number of punished crossings in the four plate test. This pro-cognitive, antidepressant-like and anxiolytic-like effect of NS9775 suggests that combining α7 nAChR agonism and triple monoamine reuptake inhibition could be a step in the evolution of pharmacological treatments of affective and/or cognitive disturbances.
    Neuropharmacology 06/2013; · 4.11 Impact Factor
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    ABSTRACT: In our search for selective agonists for the α4β2 subtype of the nicotinic acetylcholine receptors (nAChRs), we have synthesized and characterized a series of novel heterocyclic analogues of 3-(dimethylamino)butyl dimethylcarbamate (DMABC, 4). All new heterocyclic analogues, especially N,N-dimethyl-4-(1-methyl-1H-imidazol-2-yloxy)butan-2-amine (7), showed an improved binding selectivity profile in favour of α4β2 over other nAChR subtypes, primarily due to impaired binding at β4 containing receptors. This observation can be rationalized based on co-crystal structures of (R)-4 and (R)-7 bound to acetylcholine binding protein from Lymnaea stagnalis. Functional characterization at both (α4)(2)(β2)(3) and (α4)(3)(β2)(2) receptors using two-electrode voltage clamp techniques in Xenopus laevis oocytes indicate that the investigated compounds interact differently with the two receptor stoichiometries. Compound 7 is an efficacious agonist at both α4-β2 and α4-α4 binding sites while the close analog, N,N-dimethyl-4-(1,4-dimethyl-1H-imidazol-2-yloxy)butan-2-amine (9), primarily activates via α4-β2 binding sites. The results suggest that, it may be possible to rationally design compounds with specific stoichiometry preferences.
    Journal of Medicinal Chemistry 12/2012; · 5.61 Impact Factor
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    ABSTRACT: Deciphering which specific agonist-receptor interactions affect efficacy levels is of high importance, since this will ultimately aid in designing selective drugs. The novel compound NS3861 and cytisine are agonists of nicotinic acetylcholine receptors (nAChRs) and both bind with high affinity to heteromeric α3β4 and α4β2 nAChRs. However, initial data revealed that the activation patterns of the two compounds show very distinct maximal efficacy readouts at various heteromeric nAChRs. To investigate the molecular determinants behind these observations, we performed in-depth patch-clamp electrophysiological measurements of efficacy levels at heteromeric combinations of α3 and α4, with β2 and β4 subunits, and various chimeric constructs thereof. Compared to cytisine, which selectively activates receptors containing β4- but not β2 subunits, NS3861 displays the opposite β subunit preference and a complete lack of activation at α4 containing receptors. The maximal efficacy of NS3861 appeared solely dependent on the nature of the ligand-binding domain, whereas efficacy of cytisine was additionally affected by the nature of the β subunit transmembrane domain. Molecular docking to nAChR subtype homology models suggests agonist specific interactions to two different residues on the complementary subunits as responsible for the β subunit preference of both compounds. Further, a principal subunit Serine to Threonine substitution may explain the lack of NS3861 activation at α4 containing receptors. In conclusion, our results are consistent with a hypothesis where agonist interactions with the principal subunit (α) primarily determine binding affinity while interactions with key amino acids at the complementary subunit (β) affect agonist efficacy.
    Journal of Biological Chemistry 12/2012; · 4.65 Impact Factor
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    ABSTRACT: Positive allosteric modulation of α4β2 nicotinic acetylcholine (nACh) receptors could add a new dimension to the pharmacology and therapeutic approach to these receptors. The novel modulator NS9283 was therefore tested extensively. Effects of NS9283 were evaluated in vitro using fluorescence-based Ca(2+) imaging and electrophysiological voltage clamp experiments in Xenopus oocytes, mammalian cells and thalamocortical neurons. In vivo the compound was tested in models covering a range of cognitive domains in mice and rats. NS9283 was shown to increase agonist-evoked response amplitude of (α4)(3) (β2)(2) nACh receptors in electrophysiology paradigms. (α2)(3) (β2)(2) , (α2)(3) (β4)(2) and (α4)(3) (β4)(2) were modulated to comparable extents, but no effects were detected at α3-containing or any 2α : 3β stoichiometry nACh receptors. Native nACh receptors in thalamocortical neurons similarly displayed DHβE-sensitive currents that were receptive to modulation. NS9283 had favourable effects on sensory information processing, as shown by reversal of PCP-disrupted pre-pulse inhibition. NS9283 further improved performance in a rat model of episodic memory (social recognition), a rat model of sustained attention (five-choice serial reaction time task) and a rat model of reference memory (Morris water maze). Importantly, the effects in the Morris water maze could be fully reversed with mecamylamine, a blocker of nACh receptors. These results provide compelling evidence that positive allosteric modulators acting at the (α4)(3) (β2)(2) nACh receptors can augment activity across a broad range of cognitive domains, and that α4β2 nACh receptor allosteric modulation therefore constitutes a promising therapeutic approach to symptomatic treatment of cognitive impairment.
    British Journal of Pharmacology 04/2012; 167(1):164-82. · 5.07 Impact Factor
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    ABSTRACT: Neuronal cholinergic transmission is a prerequisite for proper CNS function. Consequently, disturbance of this system is associated with a number of pathophysiological conditions such as Parkinson's disease, Alzheimer's disease, schizophrenia and ADHD. Consequently, drug discovery efforts have spurred considerable research endeavours into identifying specific compounds for this system. Nicotinic acetylcholine receptors (nAChR) are ligand gated ion channels involved in cholinergic transmission. nAChRs are homo- or heteromeric pentamers with α4β2 receptors being the most abundant heteromer. The stoichiometry of α4β2 receptors can be either (α4)(3)(β2)(2) or (α4)(2)(β2)(3) representing channels with low (LS) or high (HS) sensitivity, respectively, to endogenous ligands. In the present study we applied the partial nAChR α4β2 LS and HS agonist NS3956 and the LS selective positive allosteric modulator NS9283 to investigate the role of α4β2 in Parkinson and pain models. In 6-OHDA lesioned rats, NS3956 increased rotational behaviour when rats were co-treated with nomifensine. This effect was absent in the presence of mecamylamine. In contrast, co-treatment with NS3956 and NS9283 reduced rotational behaviour in the animals. In a rat formalin pain model NS3956 induced an analgesic response that was strongly potentiated by NS9283. Finally in vitro experiments were applied to determine dopamine release from striatal minces. NS3956 induced a concentration dependent release while NS9283 was unable to potentiate agonist induced release. Together these results emphasize involvement of α4β2 nAChR in rotational and analgesic responses and confirm striatal α4β2 receptors to be of the HS form.
    Brain research 04/2012; 1458:67-75. · 2.46 Impact Factor
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    ABSTRACT: The α4β2 subtype of the nicotinic acetylcholine receptor has been pursued as a drug target for treatment of psychiatric and neurodegenerative disorders and smoking cessation aids for decades. Still, a thorough understanding of structure-function relationships of α4β2 agonists is lacking. Using binding experiments, electrophysiology and x-ray crystallography we have investigated a consecutive series of five prototypical pyridine-containing agonists derived from 1-(pyridin-3-yl)-1,4-diazepane. A correlation between binding affinities at α4β2 and the acetylcholine-binding protein from Lymnaea stagnalis (Ls-AChBP) confirms Ls-AChBP as structural surrogate for α4β2 receptors. Crystal structures of five agonists with efficacies at α4β2 from 21–76% were determined in complex with Ls-AChBP. No variation in closure of loop C is observed despite large efficacy variations. Instead, the efficacy of a compound appears tightly coupled to its ability to form a strong intersubunit bridge linking the primary and complementary binding interfaces. For the tested agonists, a specific halogen bond was observed to play a large role in establishing such strong intersubunit anchoring.
    Journal of Biological Chemistry 02/2012; 287(6):4248-4259. · 4.65 Impact Factor
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    ABSTRACT: Dopamine (DA) containing midbrain neurons play critical roles in several psychiatric and neurological diseases, including schizophrenia and attention deficit hyperactivity disorder, and the substantia nigra pars compacta neurons selectively degenerate in Parkinson's disease. Pharmacological modulation of DA receptors and transporters are well established approaches for treatment of DA-related disorders. Direct modulation of the DA system by influencing the discharge pattern of these autonomously firing neurons has yet to be exploited as a potential therapeutic strategy. Small conductance Ca(2+)-activated K(+) channels (SK channels), in particular the SK3 subtype, are important in the physiology of DA neurons, and agents modifying SK channel activity could potentially affect DA signaling and DA-related behaviors. Here we show that cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA), a subtype-selective positive modulator of SK channels (SK3 > SK2 > > > SK1, IK), decreased spontaneous firing rate, increased the duration of the apamin-sensitive afterhyperpolarization, and caused an activity-dependent inhibition of current-evoked action potentials in DA neurons from both mouse and rat midbrain slices. Using an immunocytochemically and pharmacologically validated DA release assay employing cultured DA neurons from rats, we show that CyPPA repressed DA release in a concentration-dependent manner with a maximal effect equal to the D2 receptor agonist quinpirole. In vivo studies revealed that systemic administration of CyPPA attenuated methylphenidate-induced hyperactivity and stereotypic behaviors in mice. Taken together, the data accentuate the important role played by SK3 channels in the physiology of DA neurons, and indicate that their facilitation by CyPPA profoundly influences physiological as well as pharmacologically induced hyperdopaminergic behavior.
    Frontiers in Pharmacology 01/2012; 3:11.
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    ABSTRACT: Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels that belong to the Cys-loop receptor superfamily. These receptors are allosteric proteins that exist in different conformational states, including resting (closed), activated (open), and desensitized (closed) states. The acetylcholine binding protein (AChBP) is a structural homologue of the extracellular ligand-binding domain of nAChRs. In previous studies, the degree of the C-loop radial extension of AChBP has been assigned to different conformational states of nAChRs. It has been suggested that a closed C-loop is preferred for the active conformation of nAChRs in complex with agonists whereas an open C-loop reflects an antagonist-bound (closed) state. In this work, we have determined the crystal structure of AChBP from the water snail Lymnaea stagnalis (Ls) in complex with dihydro-β-erythroidine (DHβE), which is a potent competitive antagonist of nAChRs. The structure reveals that binding of DHβE to AChBP imposes closure of the C-loop as agonists, but also a shift perpendicular to previously observed C-loop movements. These observations suggest that DHβE may antagonize the receptor via a different mechanism compared to prototypical antagonists and toxins.
    PLoS ONE 01/2012; 7(8):e40757. · 3.53 Impact Factor
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    ABSTRACT: Within the GABA(A)-receptor field, two important questions are what molecular mechanisms underlie benzodiazepine tolerance, and whether tolerance can be ascribed to certain GABA(A)-receptor subtypes. We investigated tolerance to acute anxiolytic, hypothermic and sedative effects of diazepam in mice exposed for 28-days to non-selective/selective GABA(A)-receptor positive allosteric modulators: diazepam (non-selective), bretazenil (partial non-selective), zolpidem (α(1) selective) and TPA023 (α(2/3) selective). In-vivo binding studies with [(3)H]flumazenil confirmed compounds occupied CNS GABA(A) receptors. Chronic diazepam treatment resulted in tolerance to diazepam's acute anxiolytic, hypothermic and sedative effects. In mice treated chronically with bretazenil, tolerance to diazepam's anxiolytic and hypothermic, but not sedative, effects was seen. Chronic zolpidem treatment resulted in tolerance to diazepam's hypothermic effect, but partial anxiolytic tolerance and no sedative tolerance. Chronic TPA023 treatment did not result in tolerance to diazepam's hypothermic, anxiolytic or sedative effects. OUR DATA INDICATE THAT: (i) GABA(A)-α(2)/α(3) subtype selective drugs might not induce tolerance; (ii) in rodents quantitative and temporal variations in tolerance development occur dependent on the endpoint assessed, consistent with clinical experience with benzodiazepines (e.g., differential tolerance to antiepileptic and anxiolytic actions); (iii) tolerance to diazepam's sedative actions needs concomitant activation of GABA(A)-α(1)/GABA(A)-α(5) receptors. Regarding mechanism, in-situ hybridization studies indicated no gross changes in expression levels of GABA(A) α(1), α(2) or α(5) subunit mRNA in hippocampus or cortex. Since selective chronic activation of either GABA(A) α(2), or α(3) receptors does not engender tolerance development, subtype-selective GABA(A) drugs might constitute a promising class of novel drugs.
    PLoS ONE 01/2012; 7(8):e43054. · 3.53 Impact Factor
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    ABSTRACT: The α4β2 subtype of the nicotinic acetylcholine receptor has been pursued as a drug target for treatment of psychiatric and neurodegenerative disorders and smoking cessation aids for decades. Still, a thorough understanding of structure-function relationships of α4β2 agonists is lacking. Using binding experiments, electrophysiology and x-ray crystallography we have investigated a consecutive series of five prototypical pyridine-containing agonists derived from 1-(pyridin-3-yl)-1,4-diazepane. A correlation between binding affinities at α4β2 and the acetylcholine-binding protein from Lymnaea stagnalis (Ls-AChBP) confirms Ls-AChBP as structural surrogate for α4β2 receptors. Crystal structures of five agonists with efficacies at α4β2 from 21-76% were determined in complex with Ls-AChBP. No variation in closure of loop C is observed despite large efficacy variations. Instead, the efficacy of a compound appears tightly coupled to its ability to form a strong intersubunit bridge linking the primary and complementary binding interfaces. For the tested agonists, a specific halogen bond was observed to play a large role in establishing such strong intersubunit anchoring.
    Journal of Biological Chemistry 12/2011; 287(6):4248-59. · 4.65 Impact Factor
  • Jesper T Andreasen, John P Redrobe, Elsebet Ø Nielsen
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    ABSTRACT: Emerging evidence points to an involvement of nicotinic acetylcholine receptors (nAChRs) in major depression. Nicotine improves symptoms of depression in humans and shows antidepressant-like effects in rodents. Monoamine release is facilitated by nAChR stimulation, and nicotine-evoked serotonin (5-HT) release has been shown to depend on α7 nAChR activation. The α7 nAChR agonist PNU-282987 shows no antidepressant-like activity when tested alone in the mouse forced swim (mFST) or tail suspension tests (mTST). However, in combination with a sub-active dose of the selective 5-HT reuptake inhibitor citalopram, inducing ~50% 5-HT reuptake inhibition, PNU-282987 has shown marked antidepressant-like effects in the mFST. SSR180711 is a recently described α7 nAChR agonist that has shown antidepressant-like activity in the rat forced swim test. To address the possibility that 5-HT reuptake inhibition contributes to the antidepressant-like profile of SSR180711, we compared the behavioural and biochemical profiles of PNU-282987 and SSR180711. In the mFST and mTST, SSR180711 (3-30 mg/kg, s.c.) showed dose-dependent antidepressant-like activity, while PNU-282987 (3-30 mg/kg, s.c.) showed no significant effect. The ED(50) to displace [³H]α-bungarotoxin binding was 1.7 and 5.5 mg/kg for SSR180711 and PNU-282987, respectively, suggesting that both compounds produce near-maximal α7 nAChR occupancy at the highest dose. While PNU-282987 did not affect ex vivo [³H]5-HT uptake, SSR180711 inhibited [³H]5-HT uptake with an ED₅₀ of 30 mg/kg. This degree of inhibition is similar to that observed with a citalopram dose of ~2.4 mg/kg, a dose that is normally not active in the mFST or mTST. This suggests that the antidepressant-like activity of SSR180711 may involve partial 5-HT reuptake inhibition. SSR180711 therefore represents a compound displaying the synergistic effect of α7 nAChR agonism combined with partial 5-HT reuptake inhibition previously described. The addition of α7 nAChR agonism to classical monoamine-based mechanisms may represent a novel option for the improved treatment of major depression.
    Pharmacology Biochemistry and Behavior 11/2011; 100(3):624-9. · 2.82 Impact Factor
  • Jakob Nilsson, Elsebet Østergaard Nielsen, Tommy Liljefors, Mogens Nielsen, Olov Sterner
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    ABSTRACT: Based on a pharmacophore model of the benzodiazepine binding site of the GABA(A) receptors, developed with synthetic flavones and potent 3-carbonylquinolin-4-ones, 3-alkyl- and 3-amido-6-methylisothiazoloquinolin-4-ones were designed, prepared and assayed. The suggestion that the interaction between the hydrogen bond donor site H1 with the 3-carbonyl oxygen in 3-carbonylquinolin-4-ones can be replaced by an interaction between H1 and N-2 in the isothiazoloquinolin-4-ones, was confirmed. As with the 3-carbonylquinolin-4-ones, the length of the chain in position 3 is critical for an efficient interaction with the lipophilic pockets of the pharmacophore model. The most potent 3-alkyl derivative, 3-pentyl-6-methylisothiazoloquinolin-4-one, has an affinity (K(i) value) for the benzodiazepine binding site of the GABA(A) receptors of 13 nM. However, by replacing the 3-pentyl with a 3-butyramido group an even more potent compound was obtained, with a K(i) value of 2.8 nM, indicating that the amide function facilitates additional interactions with the binding site.
    Bioorganic Chemistry 10/2011; 40(1):125-30. · 1.73 Impact Factor
  • European Neuropsychopharmacology 09/2011; 21. · 4.60 Impact Factor
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    ABSTRACT: Small-molecule α(7) nicotinic acetylcholine receptor (α(7)nAChR) agonists are currently validated for use as treatment for cognitive disturbances in schizophrenia and in Alzheimer disease. A suitable radiolabeled α(7)nAChR PET tracer would be important for in vivo quantification of α(7)nAChR binding in humans and to measure α(7)nAChR occupancy of α(7)nAChR drug candidates. Here, we present the radiosynthesis and in vivo evaluation of (11)C-NS14492 as a selective α(7)nAChR PET radioligand. The high-affinity α(7)nAChR-selective partial agonist NS14492 was radiolabeled by methylation of its desmethyl precursor using (11)C-methyl triflate. Female Danish Landrace pigs were studied at baseline and after intravenous administration of blocking doses of either the α(7)nAChR partial agonist SSR180711 or the unlabeled NS14492. (11)C-NS14492 was given as an intravenous bolus injection, and the pigs were scanned for 90 min both at baseline and in the blocked conditions. Arterial blood was collected during the scanning, plasma was counted, and parent compound fraction was determined with radio-high-performance liquid chromatography. PET data were quantified with a graphical analysis with arterial input; (11)C-NS14492 regional distribution volumes were calculated, and α(7)nAChR occupancy was determined using an occupancy plot. (11)C-NS14492 had a high uptake in the pig brain, with the highest binding in the cerebral cortex and thalamus in accordance with α(7)nAChR distribution. Pretreatment with NS14492 and SSR180711 consistently decreased distribution volumes of (11)C-NS14492 in all examined regions, in a dose-dependent manner, supporting the finding that the radioligand binds selectively to α(7)nAChR in vivo. We report here that (11)C-NS14492 is the first, to our knowledge, PET radioligand for α(7)nAChR showing a dose-dependent decline in cerebral binding after receptor blockade. This compound is considered a promising PET tracer for in vivo measurements of α(7)nAChR binding in the human brain.
    Journal of Nuclear Medicine 08/2011; 52(9):1449-56. · 5.77 Impact Factor
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    ABSTRACT: Based on a pharmacophore model of the benzodiazepine-binding site of GABA(A) receptors, a series of 2-aryl-2,6-dihydro[1,2,4]triazolo[4,3-c]quinazoline-3,5-diones (structure type I) were designed, synthesized, and identified as high-affinity ligands of the binding site. For several compounds, K(i) values of around 0.20nM were determined. They show a structural resemblance with the previously described 2-phenyl-2H-pyrazolo[4,3-c]quinolin-3(5H)-ones (II) and 2-phenyl-[1,2,4]triazolo[1,5-a]quinoxalin-4(5H)-one (III). The 9-bromo substituted compounds 8a-d were prepared in an 8-step synthesis in an overall yield of approximately 40%, and a library of 9-substituted analogues was prepared by cross-coupling reactions. Compound 8e, 21, 22, and 24 were tested on recombinant rat α(1)β(3)γ(2), α(2)β(3)γ(2), α(3)β(3)γ(2), and α(5)β(3)γ(2) subtypes, and displayed selectivity for the α(1)β(3)γ(2) isoform.
    Bioorganic & medicinal chemistry 01/2011; 19(1):111-21. · 2.82 Impact Factor
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    ABSTRACT: Enhancement of alpha7 nicotinic acetylcholine receptor (nAChR) activity is considered a therapeutic approach for ameliorating cognitive deficits present in Alzheimer's disease and schizophrenia. In this study, we describe the in vitro profile of a novel selective alpha7 nAChR agonist, 5-(6-[(3R)-1-azabicyclo[2,2,2]oct-3-yloxy]pyridazin-3-yl)-1H-indole (ABT-107). ABT-107 displayed high affinity binding to alpha7 nAChRs [rat or human cortex, [(3)H](1S,4S)-2,2-dimethyl-5-(6-phenylpyridazin-3-yl)-5-aza-2-azoniabicyclo[2.2.1]heptane (A-585539), K(i) = 0.2-0.6 nM or [(3)H]methyllycaconitine (MLA), 7 nM] that was at least 100-fold selective versus non-alpha7 nAChRs and other receptors. Functionally, ABT-107 did not evoke detectible currents in Xenopus oocytes expressing human or nonhuman alpha3beta4, chimeric (alpha6/alpha3)beta4, or 5-HT(3A) receptors, and weak or negligible Ca(2+) responses in human neuroblastoma IMR-32 cells (alpha3* function) and human alpha4beta2 and alpha4beta4 nAChRs expressed in human embryonic kidney 293 cells. ABT-107 potently evoked human and rat alpha7 nAChR current responses in oocytes (EC(50), 50-90 nM total charge, approximately 80% normalized to acetylcholine) that were enhanced by the positive allosteric modulator (PAM) 4-[5-(4-chloro-phenyl)-2-methyl-3-propionyl-pyrrol-1-yl]-benzenesulfonamide (A-867744). In rat hippocampus, ABT-107 alone evoked alpha7-like currents, which were inhibited by the alpha7 antagonist MLA. In dentate gyrus granule cells, ABT-107 enhanced spontaneous inhibitory postsynaptic current activity when coapplied with A-867744. In the presence of an alpha7 PAM [A-867744 or N-[(3R)-1-azabicyclo[2.2.2]oct-3-yl]-4-chlorobenzamide hydrochloride (PNU-120596)], the addition of ABT-107 elicited MLA-sensitive alpha7 nAChR-mediated Ca(2+) signals in IMR-32 cells and rat cortical cultures and enhanced extracellular signal-regulated kinase phosphorylation in differentiated PC-12 cells. ABT-107 was also effective in protecting rat cortical cultures against glutamate-induced toxicity. In summary, ABT-107 is a selective high affinity alpha7 nAChR agonist suitable for characterizing the roles of this subtype in pharmacological studies.
    Journal of Pharmacology and Experimental Therapeutics 09/2010; 334(3):863-74. · 3.89 Impact Factor
  • NeuroImage 08/2010; 52. · 6.25 Impact Factor
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    ABSTRACT: Nicotine increases serotonergic and noradrenergic neuronal activity and facilitates serotonin and noradrenaline release. Accordingly, nicotine enhances antidepressant-like actions of reuptake inhibitors selective for serotonin or noradrenaline in the mouse forced swim test and the mouse tail suspension test. Both high-affinity α4β2 and low-affinity α7 nicotinic acetylcholine receptor subtypes are implicated in nicotine-mediated release of serotonin and noradrenaline. The present study therefore investigated whether selective agonism of α4β2 or α7 nicotinic acetylcholine receptors would affect the mouse forced swim test activity of two antidepressants with distinct mechanisms of action, namely the selective serotonin reuptake inhibitor citalopram and the noradrenaline reuptake inhibitor reboxetine. Subthreshold and threshold doses of citalopram (3 and 10 mg/kg) or reboxetine (10 and 20 mg/kg) were tested alone and in combination with the novel α4β2-selective partial nicotinic acetylcholine receptor agonist, NS3956 (0.3 and 1.0 mg/kg) or the α7-selective nicotinic acetylcholine receptor agonist, PNU-282987 (10 and 30 mg/kg). Alone, NS3956 and PNU-282987 were devoid of activity in the mouse forced swim test, but both 1.0 mg/kg NS3956 and 30 mg/kg PNU-282987 enhanced the effect of citalopram and also reboxetine. The data suggest that the activity of citalopram and reboxetine in the mouse forced swim test can be enhanced by agonists at either α4β2 or α7 nicotinic acetylcholine receptors, suggesting that both nicotinic acetylcholine receptor subtypes may be involved in the nicotine-enhanced action of antidepressants.
    Journal of Psychopharmacology 04/2010; 25(10):1347-56. · 3.37 Impact Factor
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    ABSTRACT: In chronic studies, the classical benzodiazepine chlordiazepoxide (CDP) is often the preferred drug because, unlike other benzodiazepines, it is soluble in water. However, rapid CDP hydrolysis in solution has been described. This would diminish plasma levels in chronic minipump studies and introduce the corelease of active compounds. Therefore, the present study aimed to explore the putative hydrolysis of CDP in aqueous solution over time and to identify the hydrolysis products. Moreover, we aimed to characterize the hydrolysis products for their in vitro (3H-flunitrazepam binding and oocyte electrophysiology) and in vivo (stress-induced hyperthermia paradigm) GABAA receptor potency. CDP in solution hydrolyzed to the ketone structure demoxepam which was confirmed using mass spectrometry. The hydrolysis was concentration dependent (first-order kinetics) and temperature dependent. CDP exerted greater potency compared to demoxepam in vitro (increased activity at GABAA receptors containing α1 subunits) and in vivo (stress-induced hyperthermia), although 3H-flunitrazepam binding was comparable. The classical benzodiazepine CDP is rapidly hydrolyzed in solution to the active compound demoxepam which possesses a reduced activity at the GABAA receptor. Chronic studies that use CDP in aqueous solution should thus be interpreted with caution. It is therefore important to consider drug stability in chronic minipump applications.
    Psychopharmacology 03/2010; 208(4):555-62. · 4.06 Impact Factor

Publication Stats

2k Citations
318.47 Total Impact Points

Institutions

  • 2011–2013
    • University of Copenhagen
      • • Department of Drug Design and Pharmacology
      • • Department of Pharmacology and Pharmacotherapy
      Copenhagen, Capital Region, Denmark
  • 2008–2011
    • Lund University
      • Department of Organic Chemistry
      Lund, Skane, Sweden
  • 2001
    • Aarhus University Hospital
      Aarhus, Central Jutland, Denmark
  • 1994
    • Vanderbilt University
      • Department of Pharmacology
      Nashville, MI, United States
  • 1988
    • University of Michigan
      • Department of Neurology
      Ann Arbor, MI, United States