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1.
Sci Rep ; 13(1): 1025, 2023 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-36658269

RESUMO

Substantia nigra pars compacta (SNc) dopamine neurons are required for voluntary movement and reward learning, and advanced age is associated with motor and cognitive decline. In the midbrain, D2-type dopamine receptors located at dendrodendritic synapses between dopamine neurons control cell firing through G protein-activated potassium (GIRK) channels. We previously showed that aging disrupts dopamine neuron pacemaker firing in mice, but only in males. Here we show that the amplitude of D2-receptor inhibitory postsynaptic currents (D2-IPSCs) are moderately reduced in aged male mice. Local application of dopamine revealed a reduction in the amplitude of the D2-receptor currents in old males compared to young, pointing to a postsynaptic mechanism. Further experiments indicated that reduced D2 receptor signaling was not due to a general reduction in GIRK channel currents or degeneration of the dendritic arbor. Kinetic analysis showed no differences in D2-IPSC shape in old versus young mice or between sexes. Potentiation of D2-IPSCs by corticotropin releasing factor (CRF) was also not affected by age, indicating preservation of one mechanism of plasticity. These findings have implications for understanding dopamine transmission in aging, and reduced D2 receptor inhibition could contribute to increased susceptibility of males to SNc dopamine neuron degeneration in Parkinson's disease.


Assuntos
Dopamina , Neurônios Dopaminérgicos , Camundongos , Masculino , Animais , Neurônios Dopaminérgicos/metabolismo , Cinética , Substância Negra/metabolismo , Parte Compacta da Substância Negra/metabolismo , Receptores de Dopamina D2/metabolismo
2.
Methods Mol Biol ; 2592: 61-74, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36507985

RESUMO

Noninvasive quantitative imaging of beta-cells can provide information on changes in cellular transporters, receptors, and signaling proteins that may affect function and/or loss of mass, both of which contribute to the loss of insulin secretion and glucose regulation of patients with type 1 or type 2 diabetes (T1D/T2D). We have developed and optimized the use of two positron emission tomography (PET) radioligands, [18F]FP-(+)-DTBZ and [11C](+)-PHNO, targeting beta-cell VMAT2 and dopamine (D2/D3) receptors, respectively. Here we describe our optimized methodology for the clinical use of these two tracers for quantitative PET imaging of beta-cell biomarkers in vivo. We also briefly discuss our previous results and their implications and value towards extending the use of PET radioligand beyond the original goal of quantitative imaging of beta-cell mass to the potential to provide insight into the biology of beta-cell loss of mass and/or function and to evaluate the efficacy of therapeutics to prevent or restore functional beta-cell mass.


Assuntos
Diabetes Mellitus Tipo 2 , Receptores de Dopamina D3 , Humanos , Receptores de Dopamina D3/metabolismo , Dopamina , Receptores de Dopamina D2/metabolismo , Proteínas Vesiculares de Transporte de Monoamina/metabolismo , Diabetes Mellitus Tipo 2/diagnóstico por imagem , Diabetes Mellitus Tipo 2/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Tetrabenazina/metabolismo
3.
Synapse ; 77(1): e22254, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36099576

RESUMO

The brain plays a major role in controlling the desire to eat. This meta-analysis aimed to assess the association between dopamine receptor (DR) availability and dopamine transporter (DAT) availability, measured using positron emission tomography, and obesity. We performed a systematic search of MEDLINE (from inception to November 2020) and EMBASE (from inception to November 2020) for articles published in English using the keywords "dopamine receptor," "dopamine transporter," "obesity," and "neuroimaging." Body mass index (BMI) and the corresponding binding potential (BPND ) were extracted from figures in each study using Engauge Digitizer, version 12.1, and plotted for radiopharmaceuticals and regions of interest (ROIs). Five studies involving 119 subjects with DR and five studies including 421 subjects with DAT were eligible for inclusion in this study. In overweight or obese subjects with BMI of 25 kg/m2 or higher, DR availability from 11 C-Racloprie was negatively associated with BMI. However, DR availability from 11 C-PHNO was positively associated with BMI. DAT ratio was calculated after dividing DAT availabilities of overweight/obese BMI with mean DAT availabilities of normal BMI. The association between DAT ratio and BMI was not significant regardless of radiopharmaceuticals. In conclusion, dopamine plays a main role in the reward system with regard to obesity. Overweight and obese subjects had negative association between DR availability from 11 C-Raclopride and BMI. However, the association of DR availability with BMI was dependent on radiopharmaceuticals. DAT availability did not show the significant relationship with BMI regardless of radiopharmaceuticals.


Assuntos
Proteínas da Membrana Plasmática de Transporte de Dopamina , Compostos Radiofarmacêuticos , Humanos , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Sobrepeso , Obesidade/diagnóstico por imagem , Receptores de Dopamina D2/metabolismo
4.
Med Res Rev ; 43(1): 55-211, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36111795

RESUMO

Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D2 Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D2 R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D2 R affinity. Four to six atoms chains are optimal for D2 R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D2 R affinity. In this review, we provide a thorough overview of the therapeutic potential of D2 R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D2 R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D2 R ligands and D2 R modulators from patents are not discussed in this review.


Assuntos
Dopamina , Receptores de Dopamina D2 , Humanos , Dopamina/metabolismo , Receptores de Dopamina D2/agonistas , Receptores de Dopamina D2/metabolismo , Ligantes , Receptores Acoplados a Proteínas G
5.
Addict Biol ; 28(1): e13250, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36577731

RESUMO

Gene expression studies offer promising opportunities to better understand the processes underlying alcohol use disorder (AUD). As cell types differ in their function, gene expression profiles will typically vary across cell types. When studying bulk tissue, failure to account for this cellular diversity has a detrimental impact on the ability to detect disease associations. We therefore assayed the transcriptomes of 32,531 individual nuclei extracted from the nucleus accumbens (NAc) of nine donors with AUD and nine controls (72% male). Our study identified 17 clearly delineated cell types. We detected 26 transcriptome-wide significant differentially expressed genes (DEGs) that mainly involved medium spiny neurons with both D1-type and D2-type dopamine receptors, microglia (MGL) and oligodendrocytes. A higher than expected number of DEGs replicated in an existing single nucleus gene expression study of alcohol dependence in the prefrontal cortex (enrichment ratio 1.91, p value 0.019) with two genes remaining significant after a Bonferroni correction. Our most compelling result involved CD53 in MGL that replicated in the same cell type in the prefrontal cortex and was previously implicated in studies of DNA methylation, bulk gene expression and genetic variants. Several DEGs were previously reported to be associated with AUD (e.g., PER1 and MGAT5). The DEGs for MSN.3 seemed involved in neurodegeneration, disruption of circadian rhythms, alterations in glucose metabolism and changes in synaptic plasticity. For MGL, the DEGs implicated neuroinflammation and immune-related processes and for OLI, disruptions in myelination. This identification of the specific cell-types from which the association signals originate will be key for designing proper follow-up experiments and, eventually, novel clinical interventions.


Assuntos
Alcoolismo , Núcleo Accumbens , Masculino , Feminino , Animais , Camundongos , Núcleo Accumbens/metabolismo , Alcoolismo/genética , Alcoolismo/metabolismo , Transcriptoma , Receptores de Dopamina D1/metabolismo , Consumo de Bebidas Alcoólicas , Receptores de Dopamina D2/metabolismo , Camundongos Endogâmicos C57BL
6.
J Proteome Res ; 22(1): 259-271, 2023 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-36508580

RESUMO

Leveraging biased signaling of G protein-coupled receptors has been proposed as a promising strategy for the development of drugs with higher specificity. However, the consequences of selectively targeting G protein- or ß-arrestin-mediated signaling on cellular functions are not comprehensively understood. In this study, we utilized phosphoproteomics to gain a systematic overview of signaling induced by the four biased and balanced dopamine D2 receptor (D2R) ligands MS308, BM138, quinpirole, and sulpiride in an in vitro D2R transfection model. Quantification of 14,160 phosphosites revealed a low impact of the partial G protein agonist MS308 on cellular protein phosphorylation, as well as surprising similarities between the balanced agonist quinpirole and the inverse agonist sulpiride. Analysis of the temporal profiles of ligand-induced phosphorylation events showed a transient impact of the G protein-selective agonist MS308, whereas the ß-arrestin-preferring agonist BM138 elicited a delayed, but more pronounced response. Functional enrichment analysis of ligand-impacted phosphoproteins and treatment-linked kinases confirmed multiple known functions of D2R signaling while also revealing novel effects, for example of MS308 on sterol regulatory element-binding protein-related gene expression. All raw data were deposited in MassIVE (MSV000089457).


Assuntos
Agonismo Inverso de Drogas , Sulpirida , beta-Arrestinas/metabolismo , Quimpirol , Ligantes , Proteínas de Ligação ao GTP/metabolismo , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/agonistas , Receptores de Dopamina D2/metabolismo
7.
Bioorg Med Chem ; 78: 117131, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36571976

RESUMO

To follow up on our previous report on bivalent compounds exhibiting potent co-operative binding at dopamine D2 receptors, we modified the structure of the linker in our earlier bivalent molecules (S)-6-((9-(((R)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)nonyl)-(propyl)amino)-5,6,7,8-tetrahydronaphthalen-1-ol (Ia) and (S)-6-((10-(((R)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)decyl)(propyl)amino)-5,6,7,8-tetrahydronaphthalen-1-ol (Ib) (Fig. 1) connecting the two pharmaophoric moieties to observe any tolerance in maintaining similar affinities and potencies. Specifically, we introduced aromatic and piperazine moieties in the linker to explore their effect. Overall, similar activities at D2 receptors as observed in our earlier study was maintained in the new molecules e.g. (6S,6'S)-6,6'-((1,4-phenylenebis(ethane-2,1-diyl))bis(propylazanediyl))bis(5,6,7,8-tetrahydronaphthalen-1-ol) (D-382) (Ki, D2 = 3.88 nM). The aromatic moiety in D-382 was next functionalized by introducing hydroxyl groups to mimic polyhydroxy natural products which are known to interact with amyloidogenic proteins. Such a transformation resulted in development of compounds like 2,5-bis(2-(((S)-5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl)(propyl)amino)ethyl)benzene-1,4-diol (D-666) (Ki, D2 = 7.62 nM) which retained similar affinity and potency at D2 receptors. Such dihydroxyl compounds turned out to be potent inhibitors against aggregation and toxicity of recombinant alpha synuclein protein. The work reported here is in line with our overall goal to develop multifunctional dopamine agonist for symptomatic and disease modifying treatment of Parkinson's disease.


Assuntos
Agonistas de Dopamina , Receptores de Dopamina D2 , Receptores de Dopamina D2/metabolismo , Agonistas de Dopamina/farmacologia , Agonistas de Dopamina/química , alfa-Sinucleína , Receptores de Dopamina D3/agonistas , Piperazinas/farmacologia , Receptores de Dopamina D1
8.
Exp Brain Res ; 240(12): 3351-3360, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36350356

RESUMO

Dopamine is crucially involved in decision-making and overstimulation within dopaminergic pathways can lead to impulsive behaviour, including a desire to take risks and reduced deliberation before acting. These behavioural changes are side effects of treatment with dopaminergic drugs in Parkinson disease, but their likelihood of occurrence is difficult to predict and may be influenced by the individual's baseline endogenous dopamine state, and indeed correlate with sensation-seeking personality traits. We here collected data on a standard gambling task in healthy volunteers given either placebo, 2.5 mg of the dopamine antagonist haloperidol or 100/25 mg of the dopamine precursor levodopa in a within-subject design. We found an increase in risky choices on levodopa. Choices were, however, made faster on haloperidol with no effect of levodopa on deliberation time. Shortened deliberation times on haloperidol occurred in low sensation-seekers only, suggesting a correlation between sensation-seeking personality trait and baseline dopamine levels. We hypothesise that levodopa increases risk-taking behaviour via overstimulation at both D1 and D2 receptor level, while a single low dose of haloperidol, as previously reported (Frank and O'Reilly 2006), may block D2 receptors pre- and post-synaptically and may paradoxically lead to higher striatal dopamine acting on remaining striatal D1 receptors, causing speedier decision without influencing risk tolerance. These effects could also fit with a recently proposed computational model of the basal ganglia (Moeller and Bogacz 2019; Moeller et al. 2021). Furthermore, our data suggest that the actual dopaminergic drug effect may be dependent on the individual's baseline dopamine state, which may influence our therapeutic decision as clinicians in the future.


Assuntos
Dopamina , Haloperidol , Humanos , Dopamina/farmacologia , Haloperidol/farmacologia , Levodopa/efeitos adversos , Tomada de Decisões/fisiologia , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Dopaminérgicos/farmacologia
9.
Sci Rep ; 12(1): 19247, 2022 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-36357539

RESUMO

Sulpiride, as a D2-like dopamine (DA) receptor (D2R) antagonist, is an important antipsychotic drug in the treatment of schizophrenia. Recently, we have shown that the activation of D2Rs in the ventral pallidum (VP) modulates the activity of the ventral tegmental area (VTA) DAergic neurons. According to our hypothesis, intra-VP sulpiride can influence the motivational and learning processes, pervasively modifying the behavior of examined animals. In the present study, sulpiride was microinjected into the VP of male Wistar rats in three different doses. Morris water maze (MWM) test was applied to investigate the effects of sulpiride on spatial learning, while conditioned place preference (CPP) test was used to examine the potential rewarding effect of the drug. In order to show, whether the animals can associate the rewarding effect with an area which can be recognized only on its spatial location, we introduced a modified version of the CPP paradigm, the spatial CPP test. Our results show that the intra-VP sulpiride dose-dependently impairs learning processes. However, the largest dose of sulpiride induces place preference. Results of the spatial CPP paradigm demonstrate that the animals cannot associate the rewarding effect of the drug with the conditioning area based on its spatial location. In the CPP paradigm, locomotor activity decrease could be observed in the sulpiride-treated rats, likely because of a faster habituation with the conditioning environment. In summary, we can conclude that intra-VP sulpiride has a dual effect: it diminishes the hippocampus-dependent spatial learning processes, in addition, it has a dose-dependent rewarding effect.


Assuntos
Antipsicóticos , Prosencéfalo Basal , Masculino , Ratos , Animais , Sulpirida/farmacologia , Antipsicóticos/farmacologia , Prosencéfalo Basal/metabolismo , Morfina/farmacologia , Receptores de Dopamina D2/metabolismo , Ratos Wistar , Área Tegmentar Ventral/metabolismo
10.
J Neurosci ; 42(47): 8842-8854, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36241382

RESUMO

Ventral tegmental area (VTA) dopaminergic neurons, which are well known for their central roles in reward and motivation-related behaviors, have been shown to participate in itch processing via their projection to the nucleus accumbens (NAc). However, the functional roles of different dopamine receptor subtypes in subregions of the NAc during itch processing remain unknown. With pharmacological approaches, we found that the blockade of dopamine D1 receptors (D1R), but not dopamine D2 receptors (D2R), in the lateral shell (LaSh) of the NAc impaired pruritogen-induced scratching behavior in male mice. In contrast, pharmacological activation of D2R in both the LaSh and medial shell (MeSh) of the NAc attenuated the scratching behavior induced by pruritogens. Consistently, we found that dopamine release, as detected by a dopamine sensor, was elevated in the LaSh rather than the MeSh of the NAc at the onset of scratching behavior. Furthermore, the elevation of dopamine release in the LaSh of the NAc persisted even though itch-relieving behavior was blocked, suggesting that the dopamine signal in the NAc LaSh represents a motivational component of itch processing. Our study revealed different dynamics of dopamine release that target neurons expressing two dopamine receptors subtypes within different subregions of the NAc, and emphasized that D1R in the LaSh of the NAc is important in itch signal processing.SIGNIFICANCE STATEMENT Dopamine has been implicated in itch signal processing. However, the mechanism underlying the functional role of dopamine in itch processing remains largely unknown. Here, we examined the role of dopamine D1 receptor (D1R) and D2R in the nucleus accumbens (NAc) shell during pruritogen-induced scratching behavior. We demonstrated that D1R in the NAc lateral shell (LaSh) play an important role in motivating itch-induced scratching behavior, while activation of D2R would terminate scratching behavior. Our study revealed the diverse functional roles of dopamine signals in the NAc shell during itch processing.


Assuntos
Núcleo Accumbens , Receptores de Dopamina D1 , Masculino , Camundongos , Animais , Núcleo Accumbens/fisiologia , Receptores de Dopamina D1/metabolismo , Área Tegmentar Ventral/fisiologia , Receptores de Dopamina D2/metabolismo , Dopamina , Neurônios Dopaminérgicos/fisiologia , Prurido/induzido quimicamente
11.
J Neuroinflammation ; 19(1): 240, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-36183107

RESUMO

BACKGROUND: Major depressive disorder (MDD) is a prevalent and devastating psychiatric illness. Unfortunately, the current therapeutic practice, generally depending on the serotonergic system for drug treatment is unsatisfactory and shows intractable side effects. Multiple evidence suggests that dopamine (DA) and dopaminergic signals associated with neuroinflammation are highly involved in the pathophysiology of depression as well as in the mechanism of antidepressant drugs, which is still in the early stage of study and well worthy of investigation. METHODS: We established two chronic stress models, including chronic unpredictable mild stress (CUMS), and chronic social defeat stress (CSDS), to complementarily recapitulate depression-like behaviors. Then, hippocampal tissues were used to detect inflammation-related molecules and signaling pathways. Pathological changes in depressive mouse hippocampal astrocytes were examined by RNA sequencing. After confirming the dopamine receptor 2 (Drd2)/ß-arrestin2 signaling changes in the depressive mice brain, we then established the depressive mouse model using the ß-arrestin2 knockout mice or administrating the ß-arrestin2-biased Drd2 agonist to investigate the roles. Label-free mass spectrometry was used to identify the ß-arrestin2-binding proteins as the underlying mechanisms. We modeled neuroinflammation with interleukin-6 (IL-6) and corticosterone treatment and characterized astrocytes using multiple methods including cell viability assay, flow cytometry, and confocal immunofluorescence. RESULTS: Drd2-biased ß-arrestin2 pathway is significantly changed in the progression of depression, and genetic deletion of ß-arrestin2 aggravates neuroinflammation and depressive-like phenotypes. Mechanistically, astrocytic ß-arrestin2 retains STAT3 in the cytoplasm by structural combination with STAT3, therefore, inhibiting the JAK-STAT3 pathway-mediated inflammatory activation. Furtherly, pharmacological activation of Drd2/ß-arrestin2 pathway by UNC9995 abolishes the inflammation-induced loss of astrocytes and ameliorates depressive-like behaviors in mouse model for depression. CONCLUSIONS: Drd2/ß-arrestin2 pathway is a potential therapeutic target for depression and ß-arrestin2-biased Drd2 agonist UNC9995 is identified as a potential anti-depressant strategy for preventing astrocytic dysfunctions and relieving neuropathological manifestations in mouse model for depression, which provides insights for the therapy of depression.


Assuntos
Astrócitos , Transtorno Depressivo Maior , Animais , Astrócitos/metabolismo , Corticosterona/metabolismo , Depressão/tratamento farmacológico , Depressão/etiologia , Transtorno Depressivo Maior/metabolismo , Modelos Animais de Doenças , Dopamina/metabolismo , Agonistas de Dopamina/farmacologia , Agonistas de Dopamina/uso terapêutico , Hipocampo/metabolismo , Inflamação/metabolismo , Interleucina-6/metabolismo , Camundongos , Camundongos Knockout , Receptores de Dopamina D2/metabolismo , Estresse Psicológico/complicações , Estresse Psicológico/tratamento farmacológico , Estresse Psicológico/patologia , beta-Arrestina 1/metabolismo , beta-Arrestina 2/genética , beta-Arrestina 2/metabolismo
12.
ACS Chem Neurosci ; 13(20): 3008-3022, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36183275

RESUMO

Dopaminergic pathways control highly consequential aspects of physiology and behavior. One of the most therapeutically important and best-studied receptors in these pathways is dopamine receptor D2 (DRD2). Unfortunately, DRD2 is challenging to study with traditional molecular biological techniques, and most drugs designed to target DRD2 are ligands for many other receptors. Here, we developed probes able to both covalently bind to DRD2 using photoaffinity labeling and provide a chemical handle for detection or affinity purification. These probes behaved like good DRD2 agonists in traditional biochemical assays and were able to perform in chemical-biological assays of cell and receptor labeling. Rat whole brain labeling and affinity enrichment using the probes permitted proteomic analysis of the probes' interacting proteins. Bioinformatic study of the hits revealed that the probes bound noncanonically targeted proteins in Parkinson's disease network as well as the retrograde endocannabinoid signaling, neuronal nitric oxide synthase, muscarinic acetylcholine receptor M1, GABA receptor, and dopamine receptor D1 (DRD1) signaling networks. Follow-up analysis may yield insights into how this pathway relates specifically to Parkinson's disease symptoms or provide new targets for treatments. This work reinforces the notion that the combination of chemical biology and omics-based approaches provides a broad picture of a molecule's "interactome" and may also give insight into the pleiotropy of effects observed for a drug or perhaps indicate new applications.


Assuntos
Doença de Parkinson , Receptores de Dopamina D2 , Animais , Ratos , Receptores de Dopamina D2/metabolismo , Doença de Parkinson/tratamento farmacológico , Óxido Nítrico Sintase Tipo I/metabolismo , Ligantes , Proteômica , Endocanabinoides , Receptores de Dopamina D1 , Proteínas de Transporte , Receptores de GABA/metabolismo , Agonistas de Dopamina/farmacologia
13.
J Physiol ; 600(22): 4881-4895, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36121348

RESUMO

The activity of dopamine neurons is dependent on both intrinsic properties and afferent projections. One potent form of inhibition is mediated by the activation of two inhibitory G protein-coupled receptors, D2 and GABAB receptors. Each of these receptors activates G protein-coupled inwardly rectifying potassium (GIRK) channels. Recordings in brain slices have shown that co-activation using saturating concentrations of agonists results in occlusion of the GIRK current. The present study examined the interaction between D2 and GABAB receptors using transient applications of sub-saturating concentrations of agonists where the co-application of one agonist resulted in both facilitation and inhibition (desensitization) of the other. The heterologous facilitation was modelled based on the known cooperative interaction between the G protein ßγ subunits and GIRK channels. The results indicate that a low tonic level of G ßγ results in facilitation of GIRK current and a high level of G ßγ results in occlusion. The kinetics of the current induced by transient receptor activation is prolonged in each case. The results suggest that the cooperative interaction between G ßγ subunits and GIRK channels determines both the amplitude and kinetics of GPCR-dependent current. KEY POINTS: Inhibitory D2 and GABAB receptors modulate dopamine neuron activity through shared G protein-coupled inwardly rectifying potassium (GIRK) channels. This study reports robust bidirectional interactions between these two converging receptor pathways. Coincident activation of D2 and GABAB receptors leads to facilitation of GIRK channel currents, augmenting both amplitude and prolonging the duration of phasic responses. Activation of either D2 or GABAB receptors also acutely desensitized the GIRK channel current induced by D2 receptor activation that rapidly recovers following termination of desensitizing stimulus. Results demonstrate that the activity of either G protein-coupled receptor system must be considered in the context of other G protein-coupled receptors.


Assuntos
Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G , Receptores de GABA-B , Receptores de GABA-B/metabolismo , Receptores de Dopamina D2/metabolismo , Potássio/metabolismo , Ácido gama-Aminobutírico
14.
Commun Biol ; 5(1): 1015, 2022 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-36163254

RESUMO

Eye-blink rate has been proposed as a biomarker of the brain dopamine system, however, findings have not been consistent. This study assessed the relationship between blink rates, measured after oral placebo) (PL) and after a challenge with oral methylphenidate (MP; 60 mg) and striatal D1 receptor (D1R) (measured at baseline) and D2 receptor (D2R) availability (measured after PL and after MP) in healthy participants. PET measures of baseline D1R ([11C]NNC112) (BL-D1R) and D2R availability ([11C]raclopride) after PL (PL-D2R) and after MP (MP-D2R) were quantified in the striatum as non-displaceable binding potential. MP reduced the number of blinks and increased the time participants kept their eyes open. Correlations with dopamine receptors were only significant for the eye blink measures obtained after MP; being positive for BL-D1R in putamen and MP-D2R in caudate (PL-D2R were not significant). MP-induced changes in blink rates (PL minus MP) were negatively correlated with BL-D1R in caudate and putamen. Our findings suggest that eye blink measures obtained while stressing the dopamine system might provide a more sensitive behavioral biomarker of striatal D1R or D2R in healthy volunteers than that obtained at baseline or after placebo.


Assuntos
Metilfenidato , Corpo Estriado/diagnóstico por imagem , Corpo Estriado/metabolismo , Dopamina/metabolismo , Humanos , Metilfenidato/metabolismo , Metilfenidato/farmacologia , Racloprida/metabolismo , Racloprida/farmacologia , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo
15.
Neuropsychopharmacology ; 47(13): 2319-2329, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36100653

RESUMO

SEP-383856 (SEP-856) is a novel antipsychotic under clinical development. It displays a unique pattern of receptor interaction, with only weak (partial agonist) activity at dopamine D2 receptors, yet more potent agonist activity at the trace amine associated receptor (TAAR1) and 5-hydroxytryptamine 1 A receptor (5-HT1A). Nonetheless, these observations await independent confirmation and more detailed characterization of the in vitro and in vivo actions of SEP-856 at TAAR1 and 5-HT1A receptors would be instructive. Herein, we employed luminescence complementation technology in heterologous live cell systems, confocal microscopy, voltage clamp electrophysiology, behavioral readouts and TAAR1 knockout (KO) mice to study SEP-856 in further detail. We provide evidence for the ability of SEP-856 to activate TAAR1 at the surface plasma membrane, and show that this interaction results in Gαs recruitment (pEC50: 6.08 ± 0.22 EMAX: 96.41% ± 15.26) and by extension, to G-protein inwardly rectifying potassium (GIRK) channel activation. Using TAAR1-KO mice, we find TAAR1 to be indispensable for SEP-856 control of body temperature, baseline locomotion reduction and for "antipsychotic-like" efficacy as characterized by a reversal of dizocilipine (MK-801) mediated disruption of pre-pulse inhibition. Conversely, the inhibition by SEP-856 of MK-801 induced locomotion was unaffected in TAAR1 KO mice. SEP-856 behaved as a low-potency, partial agonist at the 5-HT1A receptor, while it partially inhibited recruitment of D2 receptor-coupled Gα and GIRK by DA and acted as a weak partial agonist with low potency at the same receptor when applied alone. Our findings corroborate and extend previous observations on the molecular substrates engaged by this unique, dual TAAR1/5-HT1A receptor agonist and potential antipsychotic that could prove to have major advantages in the treatment of schizophrenia and other psychotic disorders.


Assuntos
Antipsicóticos , Antagonistas do Receptor 5-HT1 de Serotonina , Animais , Camundongos , Antipsicóticos/farmacologia , Maleato de Dizocilpina , Camundongos Knockout , Receptor 5-HT1A de Serotonina , Receptores de Dopamina D2/metabolismo , Receptores Acoplados a Proteínas G/agonistas , Serotonina/metabolismo , Antagonistas do Receptor 5-HT1 de Serotonina/farmacologia
16.
Res Vet Sci ; 152: 427-433, 2022 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-36126509

RESUMO

Pituitary pars intermedia dysfunction (PPID) is an endocrinopathy commonly affecting old horses. It is a spontaneously occurring, progressive disease that is still poorly understood. Previous studies have observed neurodegeneration of the dopaminergic inhibition of melanotrophs, which leads to decreased dopamine (DA) in the pars intermedia (PI) and increased pro-opiomelanocortin-derived peptides circulating in plasma. However, rats knockout for the dopamine D2 receptor (D2r) similarly develop PI hypertrophy and hyperplasia. Thus, based on the current pathophysiological theory of PPID, whether the decreased DA or the D2r dysfunction leads to PPID is still unclear. To test this, a total of 28 retrospective cases of horses with PPID were collected, graded and the expression of tyrosine hydroxylase (TH) and D2r in the PI were determined. The histological and immunohistochemical results demonstrated that horses with higher tumor histological grades had reduced TH expression with increased D2r immunoreactivity colocalized in the PI (p < 0.001, p < 0.05 respectively). This correlation supports the role of DA in the pathogenesis of continuous unregulated proliferation of neoplastic cells in PI and indicates the efficiency of D2r agonists as a treatment for PPID.


Assuntos
Doenças dos Cavalos , Doenças da Hipófise , Adeno-Hipófise Parte Intermédia , Doenças dos Roedores , Cavalos , Animais , Ratos , Dopamina/metabolismo , Estudos Retrospectivos , Doenças dos Cavalos/patologia , Doenças da Hipófise/genética , Doenças da Hipófise/veterinária , Doenças da Hipófise/metabolismo , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Adeno-Hipófise Parte Intermédia/metabolismo , Adeno-Hipófise Parte Intermédia/patologia
17.
Biochem Biophys Res Commun ; 628: 40-48, 2022 11 05.
Artigo em Inglês | MEDLINE | ID: mdl-36063601

RESUMO

Dopamine D2 receptor (D2R) plays a key role in the regulation of glucose homeostasis by stimulating the secretion of many glucoregulatory hormones. Insulin resistance (IR) is associated with the pathogenesis of metabolic disorders which occurs when PI3K/Akt signaling pathway is downregulated. However, the potential involvement of D2R in insulin resistance remains unclear. In the present study, we investigated the regulation of glucose transport by D2-like receptors and discovered that activation of D2R, but not D3R or D4R, suppressed insulin-induced 2-DOG uptake and Glut4 membrane translocation in a GRK2- and Src-dependent manner. Further study revealed that activation of D2R inhibits insulin-induced phosphorylation of Akt at Thr308 and Ser473, which are hallmarks of its kinase activity, by increasing the interaction of tyrosine phosphorylated GRK2 with Akt and then preventing Akt from interacting with PDK1. Thus, this study demonstrates that Src mediated GRK2 tyrosine phosphorylation is an essential physiological event that mediates the roles of D2R in insulin resistance.


Assuntos
Quinase 2 de Receptor Acoplado a Proteína G , Resistência à Insulina , Receptores de Dopamina D2 , Animais , Dopamina , Quinase 2 de Receptor Acoplado a Proteína G/metabolismo , Glucose/metabolismo , Humanos , Insulina/metabolismo , Resistência à Insulina/genética , Resistência à Insulina/fisiologia , Camundongos , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores de Dopamina D2/metabolismo , Tirosina/metabolismo
18.
ACS Chem Neurosci ; 13(19): 2863-2873, 2022 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-36099546

RESUMO

Zebrafish (Danio rerio) are ideal model organisms for investigating nervous system function, both in health and disease. Nevertheless, functional characteristics of dopamine (DA) release and uptake regulation are still not well-understood in zebrafish. In this study, we assessed D3 autoreceptor function in the telencephalon of whole zebrafish brains ex vivo by measuring the electrically stimulated DA release ([DA]max) and uptake at carbon fiber microelectrodes with fast-scan cyclic voltammetry. Treatment with pramipexole and 7-OH-DPAT, selective D3 autoreceptor agonists, sharply decreased [DA]max. Conversely, SB277011A, a selective D3 antagonist, nearly doubled [DA]max and decreased k, the first-order rate constant for the DA uptake, to about 20% of its original value. Treatment with desipramine, a selective norepinephrine transporter blocker, failed to increase current, suggesting that our electrochemical signal arises solely from the release of DA. Furthermore, blockage of DA uptake with nomifensine-reversed 7-OH-DPAT induced decreases in [DA]max. Collectively, our data show that, as in mammals, D3 autoreceptors regulate DA release, likely by inhibiting uptake. The results of this study are useful in the further development of zebrafish as a model organism for DA-related neurological disorders such as Parkinson's disease, schizophrenia, and drug addiction.


Assuntos
Autorreceptores , Peixe-Zebra , Animais , Autorreceptores/metabolismo , Encéfalo/metabolismo , Fibra de Carbono , Desipramina , Dopamina , Estimulação Elétrica , Mamíferos/metabolismo , Nomifensina , Proteínas da Membrana Plasmática de Transporte de Norepinefrina , Pramipexol , Receptores de Dopamina D2/metabolismo , Tetra-Hidronaftalenos , Peixe-Zebra/metabolismo
19.
Protein Sci ; 31(12): e4459, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36177735

RESUMO

D3/D2 sub-specificity is a complex problem to solve. Indeed, in the absence of easy structural biology of the G-protein coupled receptors, and despite key progresses in this area, the systematic knowledge of the ligand/receptor relationship is difficult to obtain. Due to these structural biology limitations concerning membrane proteins, we favored the use of directed mutagenesis to document a rational towards the discovery of markedly specific D3 ligands over D2 ligands together with basic binding experiments. Using our methodology of stable expression of receptors in HEK cells, we constructed the gene encoding for 24 mutants and 4 chimeras of either D2 or D3 receptors and expressed them stably. Those cell lines, expressing a single copy of one receptor mutant each, were stably constructed, selected, amplified and the membranes from them were prepared. Binding data at those receptors were obtained using standard binding conditions for D2 and D3 dopamine receptors. We generated 26 new molecules derived from D2 or D3 ligands. Using 8 reference compounds and those 26 molecules, we characterized their binding at those mutants and chimeras, exemplifying an approach to better understand the difference at the molecular level of the D2 and D3 receptors. Although all the individual results are presented and could be used for minute analyses, the present report does not discuss the differences between D2 and D3 data. It simply shows the feasibility of the approach and its potential.


Assuntos
Receptores de Dopamina D2 , Receptores de Dopamina D3 , Receptores de Dopamina D3/genética , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/química , Receptores de Dopamina D2/metabolismo , Ligantes , Linhagem Celular , Mutagênese
20.
Cell Rep ; 40(13): 111440, 2022 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-36170833

RESUMO

Low dopamine D2 receptor (D2R) availability in the striatum can predispose for cocaine abuse; though how low striatal D2Rs facilitate cocaine reward is unclear. Overexpression of D2Rs in striatal neurons or activation of D2Rs by acute cocaine suppresses striatal Penk mRNA. Conversely, low D2Rs in D2-striatal neurons increases striatal Penk mRNA and enkephalin peptide tone, an endogenous mu-opioid agonist. In brain slices, met-enkephalin and inhibition of enkephalin catabolism suppresses intra-striatal GABA transmission. Pairing cocaine with intra-accumbens met-enkephalin during place conditioning facilitates acquisition of preference, while mu-opioid receptor antagonist blocks preference in wild-type mice. We propose that heightened striatal enkephalin potentiates cocaine reward by suppressing intra-striatal GABA to enhance striatal output. Surprisingly, a mu-opioid receptor antagonist does not block cocaine preference in mice with low striatal D2Rs, implicating other opioid receptors. The bidirectional regulation of enkephalin by D2R activity and cocaine offers insights into mechanisms underlying the vulnerability for cocaine abuse.


Assuntos
Transtornos Relacionados ao Uso de Cocaína , Cocaína , Analgésicos Opioides/farmacologia , Animais , Cocaína/farmacologia , Transtornos Relacionados ao Uso de Cocaína/metabolismo , Corpo Estriado/metabolismo , Encefalina Metionina/metabolismo , Encefalina Metionina/farmacologia , Encefalinas/metabolismo , Encefalinas/farmacologia , Camundongos , Antagonistas de Entorpecentes/metabolismo , Antagonistas de Entorpecentes/farmacologia , RNA Mensageiro/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo , Recompensa , Ácido gama-Aminobutírico/metabolismo
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