RESUMO
Recent clinical and preclinical studies suggest that selective activators of the M4 muscarinic acetylcholine receptor have potential as a novel treatment for schizophrenia. M4 activation inhibits striatal dopamine release by mobilizing endocannabinoids, providing a mechanism for local effects on dopamine signaling in the striatum but not in extrastriatal areas. G protein-coupled receptors (GPCRs) typically induce endocannabinoid release through activation of Gαq/11-type G proteins whereas M4 transduction occurs through Gαi/o-type G proteins. We now report that the ability of M4 to inhibit dopamine release and induce antipsychotic-like effects in animal models is dependent on co-activation of the Gαq/11-coupled mGlu1 subtype of metabotropic glutamate (mGlu) receptor. This is especially interesting in light of recent findings that multiple loss of function single nucleotide polymorphisms (SNPs) in the human gene encoding mGlu1 (GRM1) are associated with schizophrenia, and points to GRM1/mGlu1 as a gene within the "druggable genome" that could be targeted for the treatment of schizophrenia. Herein, we report that potentiation of mGlu1 signaling following thalamo-striatal stimulation is sufficient to inhibit striatal dopamine release, and that a novel mGlu1 positive allosteric modulator (PAM) exerts robust antipsychotic-like effects through an endocannabinoid-dependent mechanism. However, unlike M4, mGlu1 does not directly inhibit dopamine D1 receptor signaling and does not reduce motivational responding. Taken together, these findings highlight a novel mechanism of cross talk between mGlu1 and M4 and demonstrate that highly selective mGlu1 PAMs may provide a novel strategy for the treatment of positive symptoms associated with schizophrenia.
Assuntos
Regulação Alostérica/efeitos dos fármacos , Antipsicóticos/metabolismo , Receptor Muscarínico M4/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Animais , Ácido Glutâmico/metabolismo , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Obsessive-compulsive disorder (OCD) is a chronic, disabling condition with inadequate treatment options that leave most patients with substantial residual symptoms. Structural, neurochemical, and behavioral findings point to a significant role for basal ganglia circuits and for the glutamate system in OCD. Genetic linkage and association studies in OCD point to SLC1A1, which encodes the neuronal glutamate/aspartate/cysteine transporter excitatory amino acid transporter 3 (EAAT3)/excitatory amino acid transporter 1 (EAAC1). However, no previous studies have investigated EAAT3 in basal ganglia circuits or in relation to OCD-related behavior. Here, we report a model of Slc1a1 loss based on an excisable STOP cassette that yields successful ablation of EAAT3 expression and function. Using amphetamine as a probe, we found that EAAT3 loss prevents expected increases in (i) locomotor activity, (ii) stereotypy, and (iii) immediate early gene induction in the dorsal striatum following amphetamine administration. Further, Slc1a1-STOP mice showed diminished grooming in an SKF-38393 challenge experiment, a pharmacologic model of OCD-like grooming behavior. This reduced grooming is accompanied by reduced dopamine D1 receptor binding in the dorsal striatum of Slc1a1-STOP mice. Slc1a1-STOP mice also exhibit reduced extracellular dopamine concentrations in the dorsal striatum both at baseline and following amphetamine challenge. Viral-mediated restoration of Slc1a1/EAAT3 expression in the midbrain but not in the striatum results in partial rescue of amphetamine-induced locomotion and stereotypy in Slc1a1-STOP mice, consistent with an impact of EAAT3 loss on presynaptic dopaminergic function. Collectively, these findings indicate that the most consistently associated OCD candidate gene impacts basal ganglia-dependent repetitive behaviors.
Assuntos
Gânglios da Base/fisiologia , Transportador 3 de Aminoácido Excitatório/genética , Atividade Motora/genética , Transtorno Obsessivo-Compulsivo/genética , Transtorno Obsessivo-Compulsivo/fisiopatologia , Anfetaminas/farmacologia , Animais , Linhagem Celular , Estimulantes do Sistema Nervoso Central/farmacologia , Dopamina/metabolismo , Ácido Glutâmico/metabolismo , Asseio Animal/fisiologia , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora/fisiologia , Receptores de Dopamina D1/metabolismo , Reflexo de Sobressalto/fisiologiaRESUMO
This letter describes progress towards an M4 PAM preclinical candidate that resulted in the discovery of VU6005806/AZN-00016130. While the thieno[2,3-c]pyridazine core has been a consistent feature of key M4 PAMs, no work had previously been reported with respect to alternate functionality at the C3 position of the pyridazine ring. Here, we detail new chemistry and analogs that explored this region, and quickly led to VU6005806/AZN-00016130, which was profiled as a putative candidate. While, the ß-amino carboxamide moiety engendered solubility limited absorption in higher species precluding advancement (or requiring extensive pharmaceutical sciences formulation), VU6005806/AZN-00016130 represents a new, high quality preclinical in vivo probe.
Assuntos
Regulação Alostérica/imunologia , Receptor Muscarínico M4/imunologia , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
This letter describes progress towards an M4 PAM preclinical candidate inspired by an unexpected aldehyde oxidase (AO) metabolite of a novel, CNS penetrant thieno[2,3-c]pyridine core to an equipotent, non-CNS penetrant thieno[2,3-c]pyrdin-7(6H)-one core. Medicinal chemistry design efforts yielded two novel tricyclic cores that enhanced M4 PAM potency, regained CNS penetration, displayed favorable DMPK properties and afforded robust in vivo efficacy in reversing amphetamine-induced hyperlocomotion in rats.
Assuntos
Aldeído Oxidase/metabolismo , Miotonia Congênita/metabolismo , Receptor Muscarínico M4/metabolismo , Animais , Descoberta de Drogas , Humanos , Ratos , Relação Estrutura-AtividadeRESUMO
Cocaine use disorder (CUD) remains a debilitating health problem in the United States for which there are no Food and Drug Administration-approved treatment options. Accumulating anatomical and electrophysiological evidence indicates that the muscarinic acetylcholine receptor (mAChR) subtype 5 (M5 ) plays a critical role in the regulation of the mesolimbic dopaminergic reward circuitry, a major site of action for cocaine and other psychostimulants. In addition, M5 knockout mice exhibit reduced cocaine self-administration behaviors with no differences in sugar pellet-maintained responding relative to wild-type mice. These findings suggest that selective inhibition of M5 mAChR may provide a novel pharmacological approach for targeting CUD. Recently, we reported the synthesis and characterization of ML375, a selective negative allosteric modulator (NAM) for the rat and human M5 mAChR with optimized pharmacokinetic properties for systemic dosing in rodents. In the present study, male Sprague-Dawley rats were trained to self-administer intravenous cocaine (0.1-0.75 mg/kg/infusion) under a 10-response fixed ratio or a progressive ratio schedule of reinforcement. Under both schedules of reinforcement, ML375 produced dose-related reductions in cocaine self-administration. ML375 also modestly reduced sugar pellet-maintained responding on the 10-response, fixed ratio schedule but had no effect under a progressive ratio schedule of reinforcement. Further, ML375 did not affect general motor output as assessed by a rotarod test. Collectively, these results provide the first demonstration that selective inhibition of M5 using the M5 NAM ML375 can attenuate both the reinforcing effects and the relative strength of cocaine and suggest that M5 NAMs may represent a promising, novel treatment approach for CUD.
Assuntos
Transtornos Relacionados ao Uso de Cocaína/prevenção & controle , Cocaína/administração & dosagem , Receptor Muscarínico M5/antagonistas & inibidores , Animais , Comportamento Animal/efeitos dos fármacos , Condicionamento Operante , Modelos Animais de Doenças , Inibidores da Captação de Dopamina/administração & dosagem , Relação Dose-Resposta a Droga , Masculino , Camundongos , Ratos , Ratos Sprague-Dawley , Esquema de Reforço , Recompensa , AutoadministraçãoRESUMO
This letter describes the chemical optimization of a novel series of M4 positive allosteric modulators (PAMs) based on a 5-amino-thieno[2,3-c]pyridazine core, developed via iterative parallel synthesis, and culminating in the highly utilized rodent in vivo tool compound, VU0467154 (5). This is the first report of the optimization campaign (SAR and DMPK profiling) that led to the discovery of VU0467154, and details all of the challenges faced in allosteric modulator programs (steep SAR, species differences in PAM pharmacology and subtle structural changes affecting CNS penetration).
Assuntos
Piridazinas/farmacologia , Receptor Muscarínico M4/agonistas , Tiofenos/farmacologia , Animais , Humanos , Ligantes , Proteínas de Transporte de Nucleosídeos/metabolismo , Piridazinas/administração & dosagem , Piridazinas/síntese química , Piridazinas/farmacocinética , Ratos Sprague-Dawley , Relação Estrutura-Atividade , Tiofenos/administração & dosagem , Tiofenos/síntese química , Tiofenos/farmacocinéticaRESUMO
This letter describes the further chemical optimization of the 5-amino-thieno[2,3-c]pyridazine series (VU0467154/VU0467485) of M4 positive allosteric modulators (PAMs), developed via iterative parallel synthesis, culminating in the discovery of the non-human primate (NHP) in vivo tool compound, VU0476406 (8p). VU0476406 is an important in vivo tool compound to enable translation of pharmacodynamics from rodent to NHP, and while data related to a Parkinson's disease model has been reported with 8p, this is the first disclosure of the optimization and discovery of VU0476406, as well as detailed pharmacology and DMPK properties.
Assuntos
Descoberta de Drogas , Piridazinas/farmacologia , Tiofenos/farmacologia , Pesquisa Translacional Biomédica , Regulação Alostérica , Animais , Cristalografia por Raios X , Ligação de Hidrogênio , Piridazinas/química , Ratos , Relação Estrutura-Atividade , Tiofenos/químicaRESUMO
Negative allosteric modulators (NAMs) of metabotropic glutamate receptor subtype 5 (mGlu5) have potential applications in the treatment of fragile X syndrome, levodopa-induced dyskinesia in Parkinson disease, Alzheimer disease, addiction, and anxiety; however, clinical and preclinical studies raise concerns that complete blockade of mGlu5 and inverse agonist activity of current mGlu5 NAMs contribute to adverse effects that limit the therapeutic use of these compounds. We report the discovery and characterization of a novel mGlu5 NAM, N,N-diethyl-5-((3-fluorophenyl)ethynyl)picolinamide (VU0477573) that binds to the same allosteric site as the prototypical mGlu5 NAM MPEP but displays weak negative cooperativity. Because of this weak cooperativity, VU0477573 acts as a "partial NAM" so that full occupancy of the MPEP site does not completely inhibit maximal effects of mGlu5 agonists on intracellular calcium mobilization, inositol phosphate (IP) accumulation, or inhibition of synaptic transmission at the hippocampal Schaffer collateral-CA1 synapse. Unlike previous mGlu5 NAMs, VU0477573 displays no inverse agonist activity assessed using measures of effects on basal [(3)H]inositol phosphate (IP) accumulation. VU0477573 acts as a full NAM when measuring effects on mGlu5-mediated extracellular signal-related kinases 1/2 phosphorylation, which may indicate functional bias. VU0477573 exhibits an excellent pharmacokinetic profile and good brain penetration in rodents and provides dose-dependent full mGlu5 occupancy in the central nervous system (CNS) with systemic administration. Interestingly, VU0477573 shows robust efficacy, comparable to the mGlu5 NAM MTEP, in models of anxiolytic activity at doses that provide full CNS occupancy of mGlu5 and demonstrate an excellent CNS occupancy-efficacy relationship. VU0477573 provides an exciting new tool to investigate the efficacy of partial NAMs in animal models.
Assuntos
Agonistas GABAérgicos/farmacologia , Ácidos Picolínicos/farmacologia , Receptor de Glutamato Metabotrópico 5/efeitos dos fármacos , Regulação Alostérica/efeitos dos fármacos , Animais , Ansiolíticos/farmacologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Comportamento Animal/efeitos dos fármacos , Encéfalo/metabolismo , Relação Dose-Resposta a Droga , Descoberta de Drogas , Agonistas GABAérgicos/farmacocinética , Células HEK293 , Humanos , Fosfatos de Inositol/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Potenciais da Membrana/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Ácidos Picolínicos/farmacocinética , Piridinas/metabolismo , Ensaio Radioligante , Ratos , Receptor de Glutamato Metabotrópico 5/metabolismo , Transmissão Sináptica/efeitos dos fármacosRESUMO
This Letter describes the chemical optimization of a novel series of M4 positive allosteric modulators (PAMs) based on a 5,6-dimethyl-4-(piperidin-1-yl)thieno[2,3-d]pyrimidine core, identified from an MLPCN functional high-throughput screen. The HTS hit was potent and selective, but not CNS penetrant. Potency was maintained, while CNS penetration was improved (rat brain:plasma Kp=0.74), within the original core after several rounds of optimization; however, the thieno[2,3-d]pyrimidine core was subject to extensive oxidative metabolism. Ultimately, we identified a 6-fluoroquinazoline core replacement that afforded good M4 PAM potency, muscarinic receptor subtype selectivity and CNS penetration (rat brain:plasma Kp>10). Moreover, this campaign provided fundamentally distinct M4 PAM chemotypes, greatly expanding the available structural diversity for this exciting CNS target.
Assuntos
Piperidinas/farmacologia , Pirimidinas/farmacologia , Quinazolinas/farmacologia , Receptor Muscarínico M4/metabolismo , Tiofenos/farmacologia , Regulação Alostérica , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Humanos , Microssomos Hepáticos/metabolismo , Piperidinas/síntese química , Piperidinas/metabolismo , Pirimidinas/síntese química , Pirimidinas/metabolismo , Quinazolinas/síntese química , Quinazolinas/metabolismo , Ratos , Receptor Muscarínico M4/agonistas , Receptor Muscarínico M4/antagonistas & inibidores , Relação Estrutura-Atividade , Tiofenos/síntese química , Tiofenos/metabolismoRESUMO
While the muscarinic acetylcholine receptor mAChR subtype 5 (M5) has been studied over decades, recent findings suggest that more in-depth research is required to elucidate a thorough understanding of its physiological function related to neurological and psychiatric disorders. Our efforts to identify potent, selective, and pharmaceutically favorable next-generation M5 antagonist tool compounds have led to the discovery of a novel triazolopyridine-based series. In particular, VU6036864 (45) showed exquisite potency (human M5 IC50 = 20 nM), good subtype selectivity (>500 fold selectivity against human M1-4), desirable brain exposure (Kp = 0.68, Kp,uu = 0.65), and high oral bioavailability (%F > 100%). VU6036864 (45) and its close analogues will support further studies of M5 as advanced antagonist tool compounds and play an important role in the emerging biology of M5.
RESUMO
M(1) muscarinic acetylcholine receptors (mAChRs) represent a viable target for treatment of multiple disorders of the central nervous system (CNS) including Alzheimer's disease and schizophrenia. The recent discovery of highly selective allosteric agonists of M(1) receptors has provided a major breakthrough in developing a viable approach for the discovery of novel therapeutic agents that target these receptors. Here we describe the characterization of two novel M(1) allosteric agonists, VU0357017 and VU0364572, that display profound differences in their efficacy in activating M(1) coupling to different signaling pathways including Ca(2+) and ß-arrestin responses. Interestingly, the ability of these agents to differentially activate coupling of M(1) to specific signaling pathways leads to selective actions on some but not all M(1)-mediated responses in brain circuits. These novel M(1) allosteric agonists induced robust electrophysiological effects in rat hippocampal slices, but showed lower efficacy in striatum and no measureable effects on M(1)-mediated responses in medial prefrontal cortical pyramidal cells in mice. Consistent with these actions, both M(1) agonists enhanced acquisition of hippocampal-dependent cognitive function but did not reverse amphetamine-induced hyperlocomotion in rats. Together, these data reveal that M(1) allosteric agonists can differentially regulate coupling of M(1) to different signaling pathways, and this can dramatically alter the actions of these compounds on specific brain circuits important for learning and memory and psychosis.
Assuntos
Comportamento Animal/efeitos dos fármacos , Benzamidas/farmacologia , Compostos de Bifenilo/farmacologia , Encéfalo/efeitos dos fármacos , Agonistas Muscarínicos/farmacologia , Receptor Muscarínico M1/agonistas , Animais , Arrestinas/metabolismo , Células CHO , Cálcio/metabolismo , Linhagem Celular , Corpo Estriado/fisiologia , Cricetinae , Cricetulus , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Espaço Extracelular/fisiologia , Medo/psicologia , Perfilação da Expressão Gênica , Hipocampo/fisiologia , Humanos , Masculino , Aprendizagem em Labirinto , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Fosforilação , Córtex Pré-Frontal/fisiologia , Ratos , Ratos Sprague-DawleyRESUMO
Recent evidence suggests that inhibition of the M5 muscarinic acetylcholine receptor (mAChR) may provide a novel non-opioid mechanism for the treatment of opioid use disorder (OUD). Previous studies from our group and others have demonstrated that acute administration of the long-acting M5 negative allosteric modulator (NAM) ML375 attenuates established self-administration of cocaine, ethanol, oxycodone, and remifentanil in rats. In the present study, we characterized the effects of acute and repeated administration of the novel, short-acting M5 NAM VU6008667 on the reinforcing effects of oxycodone and reinstatement of oxycodone-seeking behaviors in male Sprague-Dawley rats, as well as on physiological withdrawal from oxycodone. Acute VU6008667 decreased oxycodone self-administration under both fixed ratio 3 (FR3) and progressive ratio (PR) schedules of reinforcement and attenuated cue-induced reinstatement of lever pressing following extinction from oxycodone self-administration, a commonly used relapse model. When administered daily to opioid-naïve rats, VU6008667 prevented acquisition of oxycodone self-administration behavior. VU6008667 had minimal effects on naloxone-precipitated withdrawal. After acute administration, VU6008667 did not inhibit sucrose self-administration and, when given chronically, delayed but did not prevent acquisition of sucrose maintained self-administration. VU6008667 also did not impact oxycodone induced anti-nociception or motor coordination, but mildly decreased novelty exploration. Finally, acute or daily VU6008667 administration did not impair cued fear conditioning. Overall, these results suggest that inhibition of the M5 mAChR may provide a novel, non-opioid based treatment for distinct aspects of OUD by inhibiting opioid intake in established OUD, reducing relapse during abstinence, and by reducing the risk of developing OUD.
Assuntos
Analgésicos Opioides , Transtornos Relacionados ao Uso de Opioides , Animais , Masculino , Ratos , Oxicodona , Ratos Sprague-Dawley , Receptores Muscarínicos , Autoadministração , Sacarose/farmacologiaRESUMO
Historically, animal models have been routinely used in the characterization of novel chemical entities (NCEs) for various psychiatric disorders. Animal models have been essential in the in vivo validation of novel drug targets, establishment of lead compound pharmacokinetic to pharmacodynamic relationships, optimization of lead compounds through preclinical candidate selection, and development of translational measures of target occupancy and functional target engagement. Yet, with decades of multiple NCE failures in Phase II and III efficacy trials for different psychiatric disorders, the utility and value of animal models in the drug discovery process have come under intense scrutiny along with the widespread withdrawal of the pharmaceutical industry from psychiatric drug discovery. More recently, the development and utilization of animal models for the discovery of psychiatric NCEs has undergone a dynamic evolution with the application of the Research Domain Criteria (RDoC) framework for better design of preclinical to clinical translational studies combined with innovative genetic, neural circuitry-based, and automated testing technologies. In this chapter, the authors will discuss this evolving role of animal models for improving the different stages of the discovery and development in the identification of next generation treatments for psychiatric disorders.
Assuntos
Transtornos Mentais , Animais , Transtornos Mentais/tratamento farmacológico , Modelos AnimaisRESUMO
Parkinson's disease (PD) is a debilitating neurodegenerative disorder associated with severe motor impairments caused by the loss of dopaminergic innervation of the striatum. Previous studies have demonstrated that positive allosteric modulators (PAMs) of metabotropic glutamate receptor 4 (mGlu4), including N-phenyl-7-(hydroxyimino) cyclopropa[b]chromen-1a-carboxamide, can produce antiparkinsonian-like effects in preclinical models of PD. However, these early mGlu4 PAMsexhibited unsuitable physiochemical properties for systemic dosing, requiring intracerebroventricular administration and limiting their broader utility as in vivo tools to further understand the role of mGlu4 in the modulation of basal ganglia function relevant to PD. In the present study, we describe the pharmacologic characterization of a systemically active mGlu4 PAM, N-(3-chlorophenyl)picolinamide (VU0364770), in several rodent PD models. VU0364770 showed efficacy alone or when administered in combination with L-DOPA or an adenosine 2A (A2A) receptor antagonist currently in clinical development (preladenant). When administered alone, VU0364770 exhibited efficacy in reversing haloperidol-induced catalepsy, forelimb asymmetry-induced by unilateral 6-hydroxydopamine (6-OHDA) lesions of the median forebrain bundle, and attentional deficits induced by bilateral 6-OHDA nigrostriatal lesions in rats. In addition, VU0364770 enhanced the efficacy of preladenant to reverse haloperidol-induced catalepsy when given in combination. The effects of VU0364770 to reverse forelimb asymmetry were also potentiated when the compound was coadministered with an inactive dose of L-DOPA, suggesting that mGlu4 PAMs may provide L-DOPA-sparing activity. The present findings provide exciting support for the potential role of selective mGlu4 PAMs as a novel approach for the symptomatic treatment of PD and a possible augmentation strategy with either L-DOPA or A2A antagonists.
Assuntos
Antagonistas do Receptor A2 de Adenosina/uso terapêutico , Levodopa/uso terapêutico , Doença de Parkinson/tratamento farmacológico , Ácidos Picolínicos/uso terapêutico , Receptores de Glutamato Metabotrópico/agonistas , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Antagonistas do Receptor A2 de Adenosina/sangue , Antagonistas do Receptor A2 de Adenosina/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/fisiopatologia , Sinalização do Cálcio/efeitos dos fármacos , Catalepsia/induzido quimicamente , Catalepsia/tratamento farmacológico , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Corpo Estriado/fisiopatologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Quimioterapia Combinada , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Ácido Glutâmico/farmacologia , Células HEK293 , Haloperidol/farmacologia , Humanos , Levodopa/metabolismo , Masculino , Monoaminoxidase/metabolismo , Doença dos Neurônios Motores/induzido quimicamente , Doença dos Neurônios Motores/tratamento farmacológico , Doença dos Neurônios Motores/metabolismo , Doença dos Neurônios Motores/patologia , Doença dos Neurônios Motores/fisiopatologia , Oxidopamina/farmacologia , Ácidos Picolínicos/sangue , Ácidos Picolínicos/metabolismo , Ácidos Picolínicos/farmacocinética , Ácidos Picolínicos/farmacologia , Ligação Proteica , Desempenho Psicomotor/efeitos dos fármacos , Pirimidinas/sangue , Pirimidinas/metabolismo , Pirimidinas/uso terapêutico , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Tempo de Reação/efeitos dos fármacos , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/antagonistas & inibidores , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Glutamato Metabotrópico/genéticaRESUMO
The muscarinic cholinergic system constitutes an important part of the neuronal circuitry that modulates normal cognition. Muscarinic receptor antagonists are well known to produce or exacerbate impairments in attention, learning, and memory. Conversely, both direct-acting muscarinic receptor agonists and indirect-acting muscarinic cholinergic agonists, such as acetylcholinesterase inhibitors, have shown cognition-enhancing properties, including improvements in normal cognitive function, reversal of cognitive deficits induced by muscarinic receptor antagonists, and attenuation of cognitive deficits in psychiatric and neurological disorders, such as Alzheimer's disease and schizophrenia. However, until recently, the lack of small molecule ligands that antagonize or activate specific muscarinic acetylcholine receptor (mAChR) subtypes with high selectivity has been a major obstacle in defining the relative contributions of individual mAChRs to different aspects of cognitive function and for the development of novel therapeutic agents. These limitations may be potentially overcome by the recent discovery of novel mAChR subtype-selective compounds, notably allosteric agonists and positive allosteric modulators, which exhibit greater selectivity for individual mAChR subtypes than previous mAChR orthosteric agonists. In preclinical studies, these novel ligands have shown promising efficacy in several models for the enhancement of cognition. In this chapter, we will review the muscarinic cholinergic circuitry and pharmacology of mAChR agonists and antagonists relevant to the modulation of different aspects of cognition in animals and clinical populations.
Assuntos
Encéfalo/efeitos dos fármacos , Transtornos Cognitivos/tratamento farmacológico , Cognição/efeitos dos fármacos , Agonistas Muscarínicos/farmacologia , Nootrópicos/farmacologia , Receptores Muscarínicos/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Acetilcolina/metabolismo , Animais , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Transtornos Cognitivos/metabolismo , Transtornos Cognitivos/fisiopatologia , Transtornos Cognitivos/psicologia , Humanos , Antagonistas Muscarínicos/farmacologia , Receptores Muscarínicos/metabolismoRESUMO
The muscarinic acetylcholine receptor (mAChR) subtype 5 (M5) represents a novel potential target for the treatment of multiple addictive disorders, including opioid use disorder. Through chemical optimization of several functional high-throughput screening hits, VU6019650 (27b) was identified as a novel M5 orthosteric antagonist with high potency (human M5 IC50 = 36 nM), M5 subtype selectivity (>100-fold selectivity against human M1-4) and favorable physicochemical properties for systemic dosing in preclinical addiction models. In acute brain slice electrophysiology studies, 27b blocked the nonselective muscarinic agonist oxotremorine-M-induced increases in neuronal firing rates of midbrain dopamine neurons in the ventral tegmental area, a part of the mesolimbic dopaminergic reward circuitry. Moreover, 27b also inhibited oxycodone self-administration in male Sprague-Dawley rats within a dose range that did not impair general motor output.
Assuntos
Transtornos Relacionados ao Uso de Opioides , Receptor Muscarínico M5 , Animais , Neurônios Dopaminérgicos , Masculino , Ratos , Ratos Sprague-Dawley , Receptor Muscarínico M1 , Receptores MuscarínicosRESUMO
Angelman syndrome (AS) is a neurogenetic disorder caused by loss of maternal UBE3A expression or mutation-induced dysfunction of its protein product, the E3 ubiquitin-protein ligase, UBE3A. In humans and rodents, UBE3A/Ube3a transcript is maternally imprinted in several brain regions, but the distribution of native UBE3A/Ube3a(1) protein expression has not been comprehensively examined. To address this, we systematically evaluated Ube3a expression in the brain and peripheral tissues of wild-type (WT) and Ube3a maternal knockout mice (AS mice). Immunoblot and immunohistochemical analyses revealed a marked loss of Ube3a protein in hippocampus, hypothalamus, olfactory bulb, cerebral cortex, striatum, thalamus, midbrain, and cerebellum in AS mice relative to WT littermates. Also, Ube3a expression in heart and liver of AS mice showed greater than the predicted 50% reduction relative to WT mice. Co-localization studies showed Ube3a expression to be primarily neuronal in all brain regions and present in GABAergic interneurons as well as principal neurons. These findings suggest that neuronal function throughout the brain is compromised in AS.
Assuntos
Síndrome de Angelman/metabolismo , Encéfalo/metabolismo , Fígado/metabolismo , Miocárdio/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Análise de Variância , Síndrome de Angelman/genética , Animais , Western Blotting , Modelos Animais de Doenças , Imuno-Histoquímica , Camundongos , Camundongos Knockout , Neurônios/metabolismo , Distribuição Tecidual , Ubiquitina-Proteína Ligases/genética , Ácido gama-Aminobutírico/metabolismoRESUMO
Degeneration of basal forebrain cholinergic circuitry represents an early event in the development of Alzheimer's disease (AD). These alterations in central cholinergic function are associated with disruptions in arousal, sleep/wake architecture, and cognition. Changes in sleep/wake architecture are also present in normal aging and may represent a significant risk factor for AD. M1 muscarinic acetylcholine receptor (mAChR) positive allosteric modulators (PAMs) have been reported to enhance cognition across preclinical species and may also provide beneficial effects for age- and/or neurodegenerative disease-related changes in arousal and sleep. In the present study, electroencephalography was conducted in young animals (mice, rats and nonhuman primates [NHPs]) and in aged mice to examine the effects of the selective M1 PAM VU0453595 in comparison with the acetylcholinesterase inhibitor donepezil, M1/M4 agonist xanomeline (in NHPs), and M1 PAM BQCA (in rats) on sleep/wake architecture and arousal. In young wildtype mice, rats, and NHPs, but not in M1 mAChR KO mice, VU0453595 produced dose-related increases in high frequency gamma power, a correlate of arousal and cognition enhancement, without altering duration of time across all sleep/wake stages. Effects of VU0453595 in NHPs were observed within a dose range that did not induce cholinergic-mediated adverse effects. In contrast, donepezil and xanomeline increased time awake in rodents and engendered dose-limiting adverse effects in NHPs. Finally, VU0453595 attenuated age-related decreases in REM sleep duration in aged wildtype mice. Development of M1 PAMs represents a viable strategy for attenuating age-related and dementia-related pathological disturbances of sleep and arousal.
Assuntos
Doenças Neurodegenerativas , Roedores , Regulação Alostérica , Animais , Nível de Alerta , Camundongos , Primatas , Piridinas , Pirróis , Ratos , Receptor Muscarínico M1 , SonoRESUMO
Recent studies suggest that subtype-selective activators of M(1)/M(4) muscarinic acetylcholine receptors (mAChRs) may offer a novel approach for the treatment of psychotic symptoms associated with schizophrenia and Alzheimer's disease. Previously developed muscarinic agonists have provided clinical data in support of this hypothesis, but failed in clinical development because of a lack of true subtype specificity and adverse effects associated with activation of other mAChR subtypes. We now report characterization of a novel highly selective agonist for the M(1) receptor with no agonist activity at any of the other mAChR subtypes, termed TBPB [1-(1'-2-methylbenzyl)-1,4'-bipiperidin-4-yl)-1H-benzo[d]imidazol-2(3H)-one]. Mutagenesis and molecular pharmacology studies revealed that TBPB activates M(1) through an allosteric site rather than the orthosteric acetylcholine binding site, which is likely critical for its unprecedented selectivity. Whole-cell patch-clamp recordings demonstrated that activation of M(1) by TBPB potentiates NMDA receptor currents in hippocampal pyramidal cells but does not alter excitatory or inhibitory synaptic transmission, responses thought to be mediated by M(2) and M(4). TBPB was efficacious in models predictive of antipsychotic-like activity in rats at doses that did not produce catalepsy or peripheral adverse effects of other mAChR agonists. Finally, TBPB had effects on the processing of the amyloid precursor protein toward the non-amyloidogenic pathway and decreased Abeta production in vitro. Together, these data suggest that selective activation of M(1) may provide a novel approach for the treatment of symptoms associated with schizophrenia and Alzheimer's disease.
Assuntos
Sítio Alostérico/fisiologia , Amiloide/metabolismo , Antipsicóticos/farmacologia , Benzimidazóis/farmacologia , Piperidinas/farmacologia , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Receptor Muscarínico M1/química , Receptor Muscarínico M1/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Benzimidazóis/administração & dosagem , Benzimidazóis/metabolismo , Células CHO , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Condutividade Elétrica , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Técnicas In Vitro , Masculino , Técnicas de Patch-Clamp , Piperidinas/administração & dosagem , Piperidinas/metabolismo , Células Piramidais/efeitos dos fármacos , Células Piramidais/fisiologia , Ratos , Ratos Sprague-Dawley , Receptor Muscarínico M1/agonistas , Receptor Muscarínico M1/efeitos dos fármacos , Receptores de Dopamina D2/metabolismo , Receptores de N-Metil-D-Aspartato/fisiologia , Transmissão Sináptica/efeitos dos fármacos , TransfecçãoRESUMO
Parkinson's Disease (PD) is marked by prominent motor symptoms that reflect striatal dopamine insufficiency. However, non-motor symptoms, including depression, are common in PD. It has been suggested that these changes reflect pathological involvement of non-dopaminergic systems. We examined regional changes in serotonin (5-HT) and norepinephrine (NE) systems in mice treated with two different 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment paradigms, at survival times of 3 or 16 weeks after the last MPTP injection. MPTP caused a decrease in striatal dopamine concentration, the magnitude of which depended on the treatment regimen and survival interval after MPTP treatment. There was significant involvement of other subcortical areas receiving a dopamine innervation, but no consistent changes in 5-HT or NE levels in subcortical sites. In contrast, we observed an enduring decrease in 5-HT and NE concentrations in both the somatosensory cortex and medial prefrontal cortex (PFC). Immunohistochemical studies also revealed a decrease in the density of PFC NE and 5-HT axons. The decrease in the cortical serotonergic innervation preferentially involved the thick beaded but not smooth fine 5-HT axons. Similar changes in the 5-HT innervation of post-mortem samples of the PFC from idiopathic PD cases were seen. Our findings point to a major loss of the 5-HT and NE innervations of the cortex in MPTP-induced parkinsonism, and suggest that loss of the beaded cortical 5-HT innervation is associated with a predisposition to the development of depression in PD.