RÉSUMÉ
Metabotropic glutamate 2/3 (mGlu2/3) receptors are of considerable interest owing to their role in modulating glutamate transmission via presynaptic, postsynaptic and glial mechanisms. As part of our ongoing efforts to identify novel ligands for these receptors, we have discovered (1S,2R,3S,4S,5R,6R)-2-amino-3-[(3,4-difluorophenyl)sulfanylmethyl]-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid; (LY3020371), a potent and selective orthosteric mGlu2/3 receptor antagonist. In this account, we characterize the effects of LY3020371 in membranes and cells expressing human recombinant mGlu receptor subtypes as well as in native rodent and human brain tissue preparations, providing important translational information for this molecule. In membranes from cells expressing recombinant human mGlu2 and mGlu3 receptor subtypes, LY3020371.HCl competitively displaced binding of the mGlu2/3 agonist ligand [3H]-459477 with high affinity (hmGlu2 Ki = 5.26 nM; hmGlu3 Ki = 2.50 nM). In cells expressing hmGlu2 receptors, LY3020371.HCl potently blocked mGlu2/3 agonist (DCG-IV)-inhibited, forskolin-stimulated cAMP formation (IC50 = 16.2 nM), an effect that was similarly observed in hmGlu3-expressing cells (IC50 = 6.21 nM). Evaluation of LY3020371 in cells expressing the other human mGlu receptor subtypes revealed high mGlu2/3 receptor selectivity. In rat native tissue assays, LY3020371 demonstrated effective displacement of [3H]-459477 from frontal cortical membranes (Ki = 33 nM), and functional antagonist activity in cortical synaptosomes measuring both the reversal of agonist-suppressed second messenger production (IC50 = 29 nM) and agonist-inhibited, K+-evoked glutamate release (IC50 = 86 nM). Antagonism was fully recapitulated in both primary cultured cortical neurons where LY3020371 blocked agonist-suppressed spontaneous Ca2+ oscillations (IC50 = 34 nM) and in an intact hippocampal slice preparation (IC50 = 46 nM). Functional antagonist activity was similarly demonstrated in synaptosomes prepared from epileptic human cortical or hippocampal tissues, suggesting a translation of the mGlu2/3 antagonist pharmacology from rat to human. Intravenous dosing of LY3020371 in rats led to cerebrospinal fluid drug levels that are expected to effectively block mGlu2/3 receptors in vivo. Taken together, these results establish LY3020371 as an important new pharmacological tool for studying mGlu2/3 receptors in vitro and in vivo. This article is part of the Special Issue entitled 'Metabotropic Glutamate Receptors, 5 years on'.
Sujet(s)
Cyclohexanes/pharmacocinétique , Antagonistes des acides aminés excitateurs/pharmacocinétique , Récepteurs métabotropes au glutamate/antagonistes et inhibiteurs , Récepteurs métabotropes au glutamate/métabolisme , Animaux , Lignée cellulaire , Cortex cérébral/effets des médicaments et des substances chimiques , Cortex cérébral/métabolisme , Cyclohexanes/composition chimique , Relation dose-effet des médicaments , Antagonistes des acides aminés excitateurs/composition chimique , Humains , Mâle , Rats , Rat Sprague-DawleyRÉSUMÉ
As part of our ongoing efforts to identify novel ligands for the metabotropic glutamate 2 and 3 (mGlu2/3) receptors, we have incorporated substitution at the C3 and C4 positions of the (1S,2R,5R,6R)-2-amino-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid scaffold to generate mGlu2/3 antagonists. Exploration of this structure-activity relationship (SAR) led to the identification of (1S,2R,3S,4S,5R,6R)-2-amino-3-[(3,4-difluorophenyl)sulfanylmethyl]-4-hydroxy-bicyclo[3.1.0]hexane-2,6-dicarboxylic acid hydrochloride (LY3020371·HCl, 19f), a potent, selective, and maximally efficacious mGlu2/3 antagonist. Further characterization of compound 19f binding to the human metabotropic 2 glutamate (hmGlu2) site was established by cocrystallization of this molecule with the amino terminal domain (ATD) of the hmGlu2 receptor protein. The resulting cocrystal structure revealed the specific ligand-protein interactions, which likely explain the high affinity of 19f for this site and support its functional mGlu2 antagonist pharmacology. Further characterization of 19f in vivo demonstrated an antidepressant-like signature in the mouse forced-swim test (mFST) assay when brain levels of this compound exceeded the cellular mGlu2 IC50 value.
Sujet(s)
Antidépresseurs/pharmacologie , Comportement animal/effets des médicaments et des substances chimiques , Découverte de médicament , Récepteurs métabotropes au glutamate/antagonistes et inhibiteurs , Animaux , Antidépresseurs/synthèse chimique , Antidépresseurs/composition chimique , Encéphale/effets des médicaments et des substances chimiques , Cyclohexanes/synthèse chimique , Cyclohexanes/composition chimique , Cyclohexanes/pharmacologie , Relation dose-effet des médicaments , Humains , Mâle , Souris , Lignées consanguines de souris , Modèles moléculaires , Structure moléculaire , Activité motrice/effets des médicaments et des substances chimiques , Récepteurs métabotropes au glutamate/composition chimique , Récepteurs métabotropes au glutamate/isolement et purification , Relation structure-activité , NatationRÉSUMÉ
Negative modulators of metabotropic glutamate 2 & 3 receptors demonstrate antidepressant-like activity in animal models and hold promise as novel therapeutic agents for the treatment of major depressive disorder. Herein we describe our efforts to prepare and optimize a series of conformationally constrained 3,4-disubstituted bicyclo[3.1.0]hexane glutamic acid analogs as orthosteric (glutamate site) mGlu2/3 receptor antagonists. This work led to the discovery of a highly potent and efficacious tool compound 18 (hmGlu2 IC50 46±14.2nM, hmGlu3 IC50=46.1±36.2nM). Compound 18 showed activity in the mouse forced swim test with a minimal effective dose (MED) of 1mg/kg ip. While in rat EEG studies it exhibited wake promoting effects at 3 and 10mg/kg ip without any significant effects on locomotor activity. Compound 18 thus represents a novel tool molecule for studying the impact of blocking mGlu2/3 receptors both in vitro and in vivo.
Sujet(s)
Antidépresseurs/composition chimique , Antidépresseurs/pharmacologie , Trouble dépressif majeur/traitement médicamenteux , Acide glutamique/analogues et dérivés , Acide glutamique/pharmacologie , Récepteurs métabotropes au glutamate/antagonistes et inhibiteurs , Animaux , Antidépresseurs/pharmacocinétique , Composés bicycliques pontés/composition chimique , Composés bicycliques pontés/pharmacocinétique , Composés bicycliques pontés/pharmacologie , Lignée cellulaire , Trouble dépressif majeur/métabolisme , Chiens , Acide glutamique/pharmacocinétique , Haplorhini , Hexanes/composition chimique , Hexanes/pharmacocinétique , Hexanes/pharmacologie , Humains , Cellules rénales canines Madin-Darby , Souris , Rats , Récepteurs métabotropes au glutamate/métabolismeRÉSUMÉ
Kappa opioid receptors and their endogenous neuropeptide ligand, dynorphin A, are densely localized in limbic and cortical areas comprising the brain reward system, and appear to play a key role in modulating stress and mood. Growing literature indicates that kappa receptor antagonists may be beneficial in the treatment of mood and addictive disorders. However, existing literature on kappa receptor antagonists has used extensively JDTic and nor-BNI which exhibit long-lasting pharmacokinetic properties that complicate experimental design and interpretation of results. Herein, we report for the first time the in vitro and in vivo pharmacological profile of a novel, potent kappa opioid receptor antagonist with excellent selectivity over other receptors and markedly improved drug-like properties over existing research tools. LY2456302 exhibits canonical pharmacokinetic properties that are favorable for clinical development, with rapid absorption (t(max): 1-2 h) and good oral bioavailability (F = 25%). Oral LY2456302 administration selectively and potently occupied central kappa opioid receptors in vivo (ED50 = 0.33 mg/kg), without evidence of mu or delta receptor occupancy at doses up to 30 mg/kg. LY2456302 potently blocked kappa-agonist-mediated analgesia and disruption of prepulse inhibition, without affecting mu-agonist-mediated effects at doses >30-fold higher. Importantly, LY2456302 did not block kappa-agonist-induced analgesia one week after administration, indicating lack of long-lasting pharmacodynamic effects. In contrast to the nonselective opioid antagonist naltrexone, LY2456302 produced antidepressant-like effects in the mouse forced swim test and enhanced the effects of imipramine and citalopram. LY2456302 reduced ethanol self-administration in alcohol-preferring (P) rats and, unlike naltrexone, did not exhibit significant tolerance upon 4 days of repeated dosing. LY2456302 is a centrally-penetrant, potent, kappa-selective antagonist with pharmacokinetic properties favorable for clinical development and activity in animal models predictive of efficacy in mood and addictive disorders.
Sujet(s)
Benzamides/pharmacologie , Dépression/traitement médicamenteux , Antagonistes narcotiques/pharmacologie , Pyrrolidines/pharmacologie , Récepteur kappa/antagonistes et inhibiteurs , Réflexe de sursaut/effets des médicaments et des substances chimiques , Filtrage sensoriel/effets des médicaments et des substances chimiques , Analgésie , Animaux , Antidépresseurs/pharmacocinétique , Antidépresseurs/pharmacologie , Antidépresseurs/usage thérapeutique , Benzamides/pharmacocinétique , Benzamides/usage thérapeutique , Modèles animaux de maladie humaine , Éthanol/administration et posologie , Mâle , Souris , Antagonistes narcotiques/pharmacocinétique , Antagonistes narcotiques/usage thérapeutique , Pyrrolidines/pharmacocinétique , Pyrrolidines/usage thérapeutique , Rats , AutoadministrationRÉSUMÉ
BACKGROUND: Selective kappa opioid receptor antagonism is a promising experimental strategy for the treatment of depression. The kappa opioid receptor antagonist, LY2456302, exhibits ~30-fold higher affinity for kappa opioid receptors over mu opioid receptors, which is the next closest identified pharmacology. METHODS: Here, we determined kappa opioid receptor pharmacological selectivity of LY2456302 by assessing mu opioid receptor antagonism using translational pupillometry in rats and humans. RESULTS: In rats, morphine-induced mydriasis was completely blocked by the nonselective opioid receptor antagonist naloxone (3mg/kg, which produced 90% mu opioid receptor occupancy), while 100 and 300 mg/kg LY2456302 (which produced 56% and 87% mu opioid receptor occupancy, respectively) only partially blocked morphine-induced mydriasis. In humans, fentanyl-induced miosis was completely blocked by 50mg naltrexone, and LY2456302 dose-dependently blocked miosis at 25 and 60 mg (minimal-to-no blockade at 4-10mg). CONCLUSIONS: We demonstrate, for the first time, the use of translational pupillometry in the context of receptor occupancy to identify a clinical dose of LY2456302 achieving maximal kappa opioid receptor occupancy without evidence of significant mu receptor antagonism.
Sujet(s)
Benzamides/pharmacologie , Antagonistes narcotiques/pharmacologie , Pupille/effets des médicaments et des substances chimiques , Pyrrolidines/pharmacologie , Récepteur kappa/antagonistes et inhibiteurs , Adolescent , Adulte , Animaux , Benzamides/sang , Études croisées , Relation dose-effet des médicaments , Méthode en double aveugle , Fentanyl/pharmacologie , Humains , Mâle , Adulte d'âge moyen , Myosis/induit chimiquement , Myosis/traitement médicamenteux , Morphine/pharmacologie , Mydriase/induit chimiquement , Mydriase/traitement médicamenteux , Naltrexone/pharmacologie , Antagonistes narcotiques/sang , Stupéfiants/pharmacologie , Pupille/physiologie , Pyrrolidines/sang , Rat Sprague-Dawley , Récepteur kappa/agonistes , Récepteur kappa/métabolisme , Jeune adulteRÉSUMÉ
Hydroxamic acid-based histone deacetylase inhibitors (HDACis) are a class of molecules with therapeutic potential currently reflected in the use of suberoylanilide hydroxamic acid (SAHA; Vorinostat) to treat cutaneous T-cell lymphomas (CTCL). HDACis may have utility beyond cancer therapy, as preclinical studies have ascribed HDAC inhibition as beneficial in areas such as heart disease, diabetes, depression, neurodegeneration, and other disorders of the central nervous system (CNS). However, little is known about the pharmacokinetics (PK) of hydroxamates, particularly with respect to CNS-penetration, distribution, and retention. To explore the rodent and non-human primate (NHP) brain permeability of hydroxamic acid-based HDAC inhibitors using positron emission tomography (PET), we modified the structures of belinostat (PXD101) and panobinostat (LBH-589) to incorporate carbon-11. We also labeled PCI 34051 through carbon isotope substitution. After characterizing the in vitro affinity and efficacy of these compounds across nine recombinant HDAC isoforms spanning Class I and Class II family members, we determined the brain uptake of each inhibitor. Each labeled compound has low uptake in brain tissue when administered intravenously to rodents and NHPs. In rodent studies, we observed that brain accumulation of the radiotracers were unaffected by the pre-administration of unlabeled inhibitors. Knowing that CNS-penetration may be desirable for both imaging applications and therapy, we explored whether a liquid chromatography, tandem mass spectrometry (LC-MS-MS) method to predict brain penetrance would be an appropriate method to pre-screen compounds (hydroxamic acid-based HDACi) prior to PET radiolabeling. LC-MS-MS data were indeed useful in identifying additional lead molecules to explore as PET imaging agents to visualize HDAC enzymes in vivo. However, HDACi brain penetrance predicted by LC-MS-MS did not strongly correlate with PET imaging results. This underscores the importance of in vivo PET imaging tools in characterizing putative CNS drug lead compounds and the continued need to discover effect PET tracers for neuroepigenetic imaging.
RÉSUMÉ
Arylphenylpyrrolidinylmethylphenoxybenzamides were found to have high affinity and selectivity for κ opioid receptors. On the basis of receptor binding assays in Chinese hamster ovary (CHO) cells expressing cloned human opioid receptors, (S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (25) had a K(i) = 0.565 nM for κ opioid receptor binding while having a K(i) = 35.8 nM for µ opioid receptors and a K(i) = 211 nM for δ opioid receptor binding. Compound 25 was also a potent antagonist of κ opioid receptors when tested in vitro using a [(35)S]-guanosine 5'O-[3-thiotriphosphate] ([(35)S]GTP-γ-S) functional assay in CHO cells expressing cloned human opioid receptors. Compounds were also evaluated for potential use as receptor occupancy tracers. Tracer evaluation was done in vivo, using liquid chromatography-tandem mass spectrometry (LC/MS/MS) methods, precluding the need for radiolabeling. (S)-3-Chloro-4-(4-((2-(pyridine-3-yl)pyrrolidin-1-yl)methyl)phenoxy)benzamide (18) was found to have favorable properties for a tracer for receptor occupancy, including good specific versus nonspecific binding and good brain uptake.
Sujet(s)
Benzamides/synthèse chimique , Pyrrolidines/synthèse chimique , Récepteur kappa/antagonistes et inhibiteurs , Animaux , Benzamides/composition chimique , Benzamides/pharmacologie , Encéphale/métabolisme , Cellules CHO , Chromatographie en phase liquide , Cricetinae , Cricetulus , Cellules HEK293 , Humains , Pyrrolidines/composition chimique , Pyrrolidines/pharmacologie , Dosage par compétition , Rats , Récepteur kappa/métabolisme , Stéréoisomérie , Relation structure-activité , Spectrométrie de masse en tandemRÉSUMÉ
The κ-opioid receptor is a widely expressed G-protein-coupled receptor that has been implicated in biological responses to pain, stress, anxiety, and depression, and its potential as a therapeutic target in these syndromes is becoming increasingly apparent. However, the prototypical selective κ-opioid antagonists have very long durations of action that have been attributed to c-Jun N-terminal kinase (JNK) 1 activation in vivo. To test generality of this proposed noncompetitive mechanism, we used C57BL/6 wild type mice to determine the durations of antagonist action of novel κ-opioid receptor ligands and examined their efficacies for JNK1 activation compared with conventional competitive antagonists. Of the 12 compounds tested, 5 had long durations of action that positively correlated with JNK activation: RTI-5989-97 [(3S)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-2-methyl-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-194 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylbutyl]-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide], RTI-5989-241 [(3R)-7-hydroxy-N-[(1S)-1-{[(3R,4R)-4-(3-methoxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxamide)], nor-binaltorphimine (nor-BNI); and (3R)-7-hydroxy-N-((1S)-1-{[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic). Seven had short durations of action and did not increase phospho-JNK-ir: RTI-5989-212[(3R)-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl}-(2-methylpropyl]-7-methoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], RTI-5989-240 [(3R)-7-hydroxy-N-[(1S)-1-[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethylpiperidin-1-yl]methyl}-(2-methylpropyl]-3-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide], JSPA0658 [(S)-3-fluoro-4-(4-((2-(3,5-dimethylphenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], JSPA071B [(S)-3-fluoro-4-(4-((2-(3,5-bis(trifluoromethyl)phenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide]. PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], PF-4455242 [2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine], FP3FBZ [(S)-3-fluoro-4-(4-((2-(3-fluorophenyl)pyrrolidin-1-yl)methyl)phenoxy)benzamide], and naloxone. After long-acting antagonist treatment, pJNK-ir did not increase in mice lacking the κ-opioid receptor; increased pJNK-ir returned to baseline by 48 h after treatment; and a second challenge with nor-BNI 72 h after the first did not increase pJNK-ir. Long-lasting antagonism and increased phospho-JNK-ir were not seen in animals lacking the JNK1 isoform. These results support the hypothesis that the duration of action of small molecule κ-opioid receptor antagonists in vivo is determined by their efficacy in activating JNK1 and that persistent inactivation of the κ-receptor does not require sustained JNK activation.
Sujet(s)
Isoenzymes/métabolisme , Mitogen-Activated Protein Kinase 8/métabolisme , Récepteur kappa/antagonistes et inhibiteurs , Animaux , Lignée cellulaire , Activation enzymatique , Humains , Souris , Souris de lignée C57BLRÉSUMÉ
An analog of the trans-3,4-dimethyl-4-(3-hydroxyphenyl)piperidine series (LY255582) exhibits high in vitro binding affinity and antagonist potency for the mu-, delta-, and kappa-opioid receptors. In vivo, LY255582 exhibits potent effects in reducing food intake and body weight in several rodent models of obesity. In the present study, we evaluated the effects of LY255582 to prevent the consumption of a highly palatable (HP) diet (a high-fat/high-carbohydrate diet) both when the food was novel and following daily limited access to the HP diet. Additionally, we examined the effects of consumption of the HP diet and of LY255582 treatment on mesolimbic dopamine (DA) signaling by in vivo microdialysis. Consumption of the HP diet increased extracellular DA levels within the nucleus accumbens (NAc) shell. Increased DA in the NAc shell was not related to the quantity of the HP diet consumed, and the DA response did not habituate following daily scheduled access to the HP diet. Interestingly, treatment with LY255582 inhibited consumption of the HP diet and the HP diet-associated increase in NAc shell DA levels. Moreover, the increased HP diet consumption observed following daily limited access to the HP diet was completely prevented by LY255582 treatment. LY255582 may be a useful tool in understanding the neural mechanisms involved in the reinforcement mechanisms regulating food intake.
Sujet(s)
Régulation de l'appétit/effets des médicaments et des substances chimiques , Comportement animal/effets des médicaments et des substances chimiques , Cyclohexanes/pharmacologie , Dopamine/métabolisme , Antagonistes narcotiques/pharmacologie , Neurones/effets des médicaments et des substances chimiques , Noyau accumbens/effets des médicaments et des substances chimiques , Pipéridines/pharmacologie , Animaux , Consommation alimentaire/effets des médicaments et des substances chimiques , Préférences alimentaires , Mâle , Microdialyse , Neurones/métabolisme , Noyau accumbens/cytologie , Noyau accumbens/métabolisme , Rats , Rat Sprague-Dawley , Récepteurs aux opioïdes/métabolisme , , Facteurs tempsRÉSUMÉ
A series of 6-bicycloaryloxynicotinamides were identified as opioid receptor antagonists at mu, kappa, and delta receptors. Compounds in the 6-(2,3,4,5-tetrahydro-1H-benzo[c]azepin-7-yloxy)nicotinamide scaffold exhibited potent in vitro functional antagonism at all three receptors.
Sujet(s)
Amides/composition chimique , Acides carboxyliques/composition chimique , Éthers/composition chimique , Éthers/pharmacologie , Antagonistes narcotiques , Résines acryliques/composition chimique , Éthers/synthèse chimique , Structure moléculaire , Récepteurs aux opioïdes/métabolisme , Relation structure-activitéRÉSUMÉ
LY255582 is a pan opioid selective receptor antagonist that has been shown to have high affinity for mu, delta, and kappa receptors in vitro. In order to better understand the in vivo opioid receptor selectivity of LY255582, we developed in vivo receptor occupancy assays in the rat for the opioid mu, kappa and delta receptors using the occupancy tracers naltrexone, GR103545 and naltriben respectively. Individual assays for each target were established and then a "triple tracer" assay was created where all three tracers were injected simultaneously, taking advantage of LC/MS/MS technology to selectively monitor brain tracer levels. This is the first report of a technique to concurrently measure receptor specific occupancy at three opioid receptors in the same animal. The opioid subtype selective antagonists cyprodime, JDTic and naltrindole were used to validate selectivity of the assay. Examination of LY255582 in dose-occupancy experiments demonstrated a relative order of potency of mu>kappa>delta, reproducing the previously reported order determined with in vitro binding.
Sujet(s)
Encéphale/métabolisme , Cyclohexanes/pharmacologie , Antagonistes narcotiques/pharmacologie , Pipéridines/pharmacologie , Récepteur delta/métabolisme , Récepteur kappa/métabolisme , Récepteur mu/métabolisme , Animaux , Fixation compétitive , Encéphale/effets des médicaments et des substances chimiques , Chromatographie en phase liquide/méthodes , Cyclohexanes/administration et posologie , Injections veineuses , Mâle , Souris , Souris knockout , Antagonistes narcotiques/administration et posologie , Obésité/traitement médicamenteux , Obésité/métabolisme , Pipéridines/administration et posologie , Liaison aux protéines , Rats , Récepteur delta/antagonistes et inhibiteurs , Récepteur kappa/antagonistes et inhibiteurs , Récepteur mu/antagonistes et inhibiteurs , Récepteur mu/génétique , Spectrométrie de masse en tandem/méthodesRÉSUMÉ
In humans, kappa opioid receptor agonists produce, among other effects, sedation and difficulty concentrating, suggesting that they may disrupt attention. The purpose of the present studies was therefore to evaluate the effects of kappa opioid receptor agonists on attention as assessed by a 5-choice serial reaction time task in rats. The kappa opioid receptor agonists (+)-U69,593 (0.1-0.56mg/kg), (+/-)-U50,488 (1.0-5.6mg/kg) and racemic GR89,696 (0.0003-0.01mg/kg) all produced dose-related decreases in the percentage of trials terminated by a correct or incorrect response and increases in the percentage of omissions. In contrast, the peripherally restricted opioid agonist ICI-204,448 was ineffective (1.0-10mg/kg). Moreover, the effects of GR89,696 were stereoselective in that (R)-GR89,696 was approximately equipotent to racemic GR89,696 and approximately 100-fold more potent than (S)-GR89,696. The opioid receptor antagonist naltrexone (0.3-3mg/kg) administered alone had no effects on performance. However, naltrexone, over the dose-range of 0.03-1.0mg/kg, produced a dose-related antagonism of the disruption produced by U69,593 (0.56mg/kg). In contrast, naltrexone, over the dose-range of 0.01-0.3mg/kg produced a dose-related antagonism of morphine (5.6mg/kg). Recent evidence has suggested that kappa opioid receptor agonists decrease dopaminergic and noradrenergic neurotransmission in prefrontal cortex and locus coeruleus. Together with previous findings, the present data indicate that kappa opioid receptor agonists disrupt performance of this attention task by decreasing the probability of responding by specific actions at central kappa opioid receptors, perhaps by decreasing dopaminergic and noradrenergic neurotransmission.
Sujet(s)
Analgésiques/pharmacologie , Attention/effets des médicaments et des substances chimiques , Comportement de choix/effets des médicaments et des substances chimiques , Temps de réaction/effets des médicaments et des substances chimiques , Récepteur kappa/agonistes , Analyse de variance , Animaux , Comportement animal/effets des médicaments et des substances chimiques , Relation dose-effet des médicaments , Mâle , Naltrexone/pharmacologie , Antagonistes narcotiques/pharmacologie , Stimulation lumineuse , Rats , Rat Sprague-Dawley , Récepteur kappa/métabolismeRÉSUMÉ
A structurally unique and new class of opioid receptor antagonists (OpRAs) that bear no structural resemblance with morphine or endogenous opioid peptides has been discovered. A series of carboxamido-biaryl ethers were identified as potent receptor antagonists against mu, kappa and delta opioid receptors. The structure-activity relationship indicated para-substituted aryloxyaryl primary carboxamide bearing an amine tether on the distal phenyl ring was optimal for potent in vitro functional antagonism against three opioid receptor subtypes.
Sujet(s)
Éthers/synthèse chimique , Éthers/pharmacologie , Antagonistes narcotiques , Animaux , Cellules CHO , Cricetinae , Cricetulus , Conception de médicament , Guanosine 5'-O-(3-thiotriphosphate)/antagonistes et inhibiteurs , Humains , Conformation moléculaire , Récepteur delta/antagonistes et inhibiteurs , Récepteur kappa/antagonistes et inhibiteurs , Récepteur mu/antagonistes et inhibiteurs , Relation structure-activitéRÉSUMÉ
Differences in the anorectic activity of morphinan (e.g., naltrexone) and 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine (4PP) opioid receptor antagonists have been described. In an attempt to explain these differences, the influence of Na(+) on opioid binding affinity and functional activity of 4PP antagonists was compared to other opioid antagonists. The binding affinities of neutral antagonists were unaffected by the addition of Na(+), whereas that for the peptide, inverse agonist N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH (ICI174864) was increased. Similarly, the binding affinities of the 4PP antagonist (3R,4R)-1-((S)-3-hydroxy-3-cyclohexylpropyl)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidine (LY255582) and other 4PP antagonists were increased in the presence of Na(+) with the greatest effects at the delta opioid receptor followed by the mu and kappa opioid receptors, respectively. Similar to ICI174864, 4PP antagonists were found to inhibit basal GTPgamma[(35)S] binding at the delta opioid receptor indicating inverse agonist activity. A correlation was observed between the binding affinities in the presence of Na(+), the inverse agonist potency, and the anorectic potency of 4PP antagonists. These data suggest that 4PP antagonists differ from morphinan antagonists in their inverse agonist activity and suggest a relationship between inverse agonism and anorectic activity.
Sujet(s)
Anorexigènes , Antagonistes narcotiques/pharmacologie , Pipéridines/pharmacologie , Récepteurs aux opioïdes/agonistes , Sodium/métabolisme , Animaux , Fixation compétitive/effets des médicaments et des substances chimiques , Cellules CHO , Membrane cellulaire/effets des médicaments et des substances chimiques , Membrane cellulaire/métabolisme , Cricetinae , Cyclohexanes/pharmacologie , Diprénorphine/métabolisme , Diprénorphine/pharmacologie , Relation dose-effet des médicaments , Consommation alimentaire/effets des médicaments et des substances chimiques , 2-Alanine-5-glycine-4-méthylphénylalanine-enképhaline/pharmacologie , Guanosine 5'-O-(3-thiotriphosphate)/métabolisme , Ligands , Naltrexone/pharmacologie , Dosage par compétition , Rats , Rat Zucker , Récepteurs aux opioïdes/métabolisme , Récepteur delta/agonistesRÉSUMÉ
Analogues of 3,4-dimethyl-4-(3-hydroxyphenyl)piperidines are high affinity inverse agonists for micro-, delta- and kappa-opioid receptors. To characterize inverse agonist binding, we synthesized a high specific activity radioligand from this series, [3H]LY515300 (3-[1-((3-cyclohexyl-[3,4-3H(2)])-3(R,S)-hydroxypropyl)-3(R),4(R)-dimethylpiperidin-4-yl]phenol). In membranes expressing cloned human opioid receptors, [3H]LY515300 binding was saturable and exhibited low nonspecific binding. [3H]LY515300 bound with high affinity to the micro- (K(d)=0.07 nM), delta- (K(d)=0.92 nM) and kappa-(K(d)=0.45 nM) opioid receptors. High affinity [3H]LY515300 binding to all opioid receptors was Na(+)-dependent, a characteristic of inverse agonists. Displacement by standard opioid compounds yielded K(i) values consistent with their known opioid receptor affinities. Autoradiographic localization of specific [3H]LY515300 binding in rat and guinea pig brain was high in areas known to express high levels of opioid (particularly micro-opioid receptor) binding sites including the caudate, nucleus accumbens, and nucleus tractus solitarius. Thus, [3H]LY515300 is the first radiolabeled opioid receptor inverse agonist useful for the study of opioid receptors in cell lines and native tissues.
Sujet(s)
Pipéridines/métabolisme , Récepteurs aux opioïdes/agonistes , Récepteurs aux opioïdes/métabolisme , Sodium/métabolisme , Animaux , Encéphale/effets des médicaments et des substances chimiques , Encéphale/métabolisme , Cellules CHO , Cricetinae , Relation dose-effet des médicaments , Cochons d'Inde , Humains , Mâle , Pipéridines/composition chimique , Pipéridines/pharmacologie , Liaison aux protéines/effets des médicaments et des substances chimiques , Liaison aux protéines/physiologie , Rats , Rat Sprague-Dawley , Sodium/pharmacologie , Tritium/métabolismeRÉSUMÉ
Agonists to opioid receptors induce a positive energy balance, whereas antagonists at these receptors reduce food intake and body weight in rodent models of obesity. An analog of 3,4-dimethyl-4-(3-hydroxyphenyl)piperidine, LY255582, is a potent non-morphinan antagonist for mu-, kappa-, and delta-receptors (K(i) of 0.4, 2.0, and 5.2 nM, respectively). In the present study, we examined the effects of oral LY255582 treatment on caloric intake, calorie expenditure, and body composition in dietary-induced obese rats. Acute oral treatment of LY255582 produced a dose-dependent decrease in energy intake and respiratory quotient (RQ), which correlated with the occupancy of central opioid receptors. Animals receiving chronic oral treatment with LY255582 for 14 days maintained a negative energy balance that was sustained by increased lipid use. Analysis of body composition revealed a reduction in fat mass accretion, with no change in lean body mass, in animals treated with LY255582. Therefore, chronic treatment with LY255582 reduces adipose tissue mass by reducing energy intake and stimulating lipid use.