RESUMO
The D1R and D3R receptors functionally and synergistically interact in striatonigral neurons. Dopaminergic denervation turns this interaction antagonistic, which is correlated with a decrement in D3nf isoform and an increment in D3R membranal expression. The mechanisms of such changes in D3R are attributed to the dysregulation of the expression of their isoforms. The cause and mechanism of this phenomenon remain unknown. Dopaminergic denervation produces a decrement in D1R and PKA activity; we propose that the lack of phosphorylation of PTB (regulator of alternative splicing) by PKA produces the dysregulation of D3R splicing and changes D3R functionality. By using in silico analysis, we found that D3R mRNA has motifs for PTB binding and, by RIP, co-precipitates with PTB. Moreover, D1R activation via PKA promotes PTB phosphorylation. Acute and 5-day D1R blockade decreases the expression of D3nf mRNA. The 5-day treatment reduces D3R, D3nf, and PTB protein in the cytoplasm and increases D3R in the membrane and PTB in the nucleus. Finally, the blockade of D1R mimics the effect of dopaminergic denervation in D1R and D3R signaling. Thus, our data indicate that through PKAâPTB, D1R modulates D3R splicing, expression, and signaling, which are altered during D1R blockade or the lack of stimulation in dopaminergic denervation.
RESUMO
Several types of sensory perception have circadian rhythms. The spinal cord can be considered a center for controlling circadian rhythms by changing clock gene expression. However, to date, it is not known if mechanonociception itself has a circadian rhythm. The hypothalamic A11 area represents the primary source of dopamine (DA) in the spinal cord and has been found to be involved in clock gene expression and circadian rhythmicity. Here, we investigate if the paw withdrawal threshold (PWT) has a circadian rhythm, as well as the role of the dopaminergic A11 nucleus, DA, and DA receptors (DR) in the PWT circadian rhythm and if they modify clock gene expression in the lumbar spinal cord. Naïve rats showed a circadian rhythm of the PWT of almost 24 h, beginning during the night-day interphase and peaking at 14.63 h. Similarly, DA and DOPAC's spinal contents increased at dusk and reached their maximum contents at noon. The injection of 6-hydroxydopamine (6-OHDA) into the A11 nucleus completely abolished the circadian rhythm of the PWT, reduced DA tissue content in the lumbar spinal cord, and induced tactile allodynia. Likewise, the repeated intrathecal administration of D1-like and D2-like DA receptor antagonists blunted the circadian rhythm of PWT. 6-OHDA reduced the expression of Clock and Per1 and increased Per2 gene expression during the day. In contrast, 6-OHDA diminished Clock, Bmal, Per1, Per2, Per3, Cry1, and Cry2 at night. The repeated intrathecal administration of the D1-like antagonist (SCH-23390) reduced clock genes throughout the day (Clock and Per2) and throughout the night (Clock, Per2 and Cry1), whereas it increased Bmal and Per1 throughout the day. In contrast, the intrathecal injection of the D2 receptor antagonists (L-741,626) increased the clock genes Bmal, Per2, and Per3 and decreased Per1 throughout the day. This study provides evidence that the circadian rhythm of the PWT results from the descending dopaminergic modulation of spinal clock genes induced by the differential activation of spinal DR.
RESUMO
BACKGROUND: Basolateral amygdala (BLA) excitatory projections to medial prefrontal cortex (PFC) play a key role controlling stress behavior, pain, and fear. Indeed, stressful events block synaptic plasticity at the BLA-PFC circuit. The stress responses involve the action of corticotrophin releasing factor (CRF) through type 1 and type 2 CRF receptors (CRF1 and CRF2). Interestingly, it has been described that dopamine receptor 1 (D1R) and CRF peptide have a modulatory role of BLA-PFC transmission. However, the participation of CRF1 and CRF2 receptors in BLA-PFC synaptic transmission still is unclear. METHODS: We used in vivo microdialysis to determine dopamine and glutamate (GLU) extracellular levels in PFC after BLA stimulation. Immunofluorescence anatomical studies in rat PFC synaptosomes devoid of postsynaptic elements were performed to determine the presence of D1R and CRF2 receptors in synaptical nerve endings. RESULTS: Here, we provide direct evidence of the opposite role that CRF receptors exert over dopamine extracellular levels in the PFC. We also show that D1R colocalizes with CRF2 receptors in PFC nerve terminals. Intra-PFC infusion of antisauvagine-30, a CRF2 receptor antagonist, increased PFC GLU extracellular levels induced by BLA activation. Interestingly, the increase in GLU release observed in the presence of antisauvagine-30 was significantly reduced by incubation with SCH23390, a D1R antagonist. CONCLUSION: PFC CRF2 receptor unmasks D1R effect over glutamatergic transmission of the BLA-PFC circuit. Overall, CRF2 receptor emerges as a new modulator of BLA to PFC glutamatergic transmission, thus playing a potential role in emotional disorders.
Assuntos
Complexo Nuclear Basolateral da Amígdala/metabolismo , Dopamina/metabolismo , Ácido Glutâmico/metabolismo , Córtex Pré-Frontal/metabolismo , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Receptores de Dopamina D1/metabolismo , Animais , Masculino , Microdiálise , Ratos , Ratos Sprague-DawleyRESUMO
Dopamine replacement therapy with L-3,4-dihydroxyphenylalanine (L-DOPA) is the only temporary therapy for Parkinson's disease (PD), but it triggers dyskinesia over time. Since dyskinesia is associated with increased neuronal firing that bolsters purinergic signaling, we now tested whether the selective and blood-brain barrier-permeable P2X7 receptor antagonist Brilliant Blue-G (BBG, 22.5-45 mg/kg ip) attenuated behavioral, neurochemical and biochemical alterations in rats turned hemiparkinsonian upon unilateral striatal injection of 6-hydroxydopamine (6-OHDA) and treated daily with L-DOPA (30 mg/kg by gavage) for 22 days. The blockade of P2X7 receptors decreased L-DOPA-induced dyskinesia and motor incoordination in hemiparkinsonian rats. In parallel, BBG treatment rebalanced the altered dopamine D1 and D2 receptor density and signaling as well as some neuroinflammation-associated parameters in the striatum and substantia nigra. These findings herald a hitherto unrecognized role for purinergic signaling in the etiopathology of dyskinesia and prompt P2X7 receptor antagonists as novel candidate anti-dyskinesia drugs.
RESUMO
One manner in which G protein-coupled receptors potentiate, increase, and change their functionality is through the formation of heteromers in a specific cellular context. Previously, we have shown that dopamine D1 receptor (D1R) and the corticotropin releasing factor receptor type-2α (CRF2α) heteromerize in HEK293T cells, enabling D1R to mobilize intracellular calcium in response to D1R agonists. In this study, we further investigated the pharmacological properties of the CRF2α-D1R heteromer and the consequences of the heteromerization in their signaling and subcellular localization when both receptors are co-expressed in HEK293T cells. Using immunoprecipitation assays, we observed that the addition of 10 µM dopamine in the incubation medium significantly decreased the amount of CRF2α on the cell surface of cells expressing both receptors. The presence of agonists of both receptors increased the interaction between CRF2α and D1R as assessed by co-immunoprecipitation. However, the presence of agonists of both receptors resulted in a lesser efficient activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase. Using a synaptosomal preparation of rat prefrontal cortex devoid of post-synaptic elements, we found that CRF2α and D1R co-localize in synaptic terminals of the rat medial prefrontal cortex and that the simultaneous activation of both receptors also occluded phosphorylation of extracellular signal-regulated kinase. These results strengthen the idea that the heteromer CRF2a-D1R is an entity functionally different from each receptor that composes it and suggests that its formation is enhanced by CRF and dopamine co-transmission, as occurs in stress and addiction.
Assuntos
Sistema de Sinalização das MAP Quinases/fisiologia , Receptor Cross-Talk/fisiologia , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Receptores de Dopamina D1/metabolismo , Animais , Hormônio Liberador da Corticotropina/metabolismo , Hormônio Liberador da Corticotropina/farmacologia , Dopamina/metabolismo , Dopamina/farmacologia , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Ratos , Ratos Sprague-Dawley , Receptor Cross-Talk/efeitos dos fármacos , Receptores de Hormônio Liberador da Corticotropina/agonistas , Receptores de Dopamina D1/agonistasRESUMO
BACKGROUND: Osteogenic differentiation of bone mesenchymal stem cells (BMSCs) is regulated by numerous signaling pathways. Dopamine (DA), a neurotransmitter, has previously been demonstrated to induce new bone formation by stimulating the receptors on BMSCs, but the essential mediators of DA-induced osteogenic signaling remain unclear. METHODS: In this work, we evaluated the influence of both dopamine D1 and D2 receptor activation on BMSC osteogenic differentiation. Gene and protein expression of osteogenic-related markers were tested. The direct binding of transcriptional factor, Runx2, to those markers was also investigated. Additionally, cellular differentiation-associated signaling pathways were evaluated. RESULTS: We showed that the expression level of the D1 receptor on BMSCs increased during osteogenic differentiation. A D1 receptor agonist, similar to DA, induced the osteogenic differentiation of BMSCs, and this phenomenon was effectively inhibited by a D1 receptor antagonist or by D1 receptor knockdown. Furthermore, the suppression of protein kinase A (PKA), an important kinase downstream of the D1 receptor, successfully inhibited DA-induced BMSC osteogenic differentiation and decreased the phosphorylation of ERK1/2. Compared with P38, MAPK, and JNK, DA mainly induced the phosphorylation of ERK1/2 and led to the upregulation of Runx2 transcriptional activity, thus facilitating BMSC osteogenic differentiation. On the other hand, an ERK1/2 inhibitor could reverse these effects. CONCLUSIONS: Taken together, these results suggest that ERK signaling may play an essential role in coordinating the DA-induced osteogenic differentiation of BMSCs by D1 receptor activation.
Assuntos
Células da Medula Óssea/metabolismo , Sistema de Sinalização das MAP Quinases/genética , Células-Tronco Mesenquimais/metabolismo , Osteogênese/genética , Receptores de Dopamina D1/genética , Animais , Células da Medula Óssea/citologia , Diferenciação Celular , Proliferação de Células , Humanos , Camundongos , Transdução de SinaisRESUMO
RATIONALE: Histamine H3 receptors (H3Rs) are co-expressed with dopamine D1 receptors (D1Rs) by striato-nigral medium spiny GABAergic neurons, where they functionally antagonize D1R-mediated responses. OBJECTIVES AND METHODS: We examined whether the chronic administration of the H3R agonist immepip modifies dyskinesias induced by L-3,4-dihydroxyphenylalanine, L-Dopa (LIDs), in rats lesioned with 6-hydroxydopamine in the substantia nigra pars compacta, and the effect of D1R and H3R co-activation on glutamate and GABA content in dialysates from the dorsal striatum of naïve rats. RESULTS: The systemic administration (i.p.) of L-Dopa for 14 days significantly increased axial, limb, and orolingual abnormal involuntary movements (AIMs) compared with the vehicle group. The chronic administration of the H3R agonist immepip alongside L-Dopa significantly decreased axial, limb, and orolingual AIMs compared with L-Dopa alone, but AIMs returned to previous values on immepip withdrawal. Chronic immepip was ineffective when administered prior to L-Dopa. The chronic administration of immepip significantly decreased GABA and glutamate content in striatal dialysates, whereas the administration of L-Dopa alone increased GABA and glutamate content. CONCLUSIONS: These results indicate that chronic H3R activation reduces LIDs, and the effects on striatal GABA and glutamate release provide evidence for a functional interaction between D1Rs and H3Rs.
Assuntos
Discinesia Induzida por Medicamentos/tratamento farmacológico , Agonistas dos Receptores Histamínicos/administração & dosagem , Imidazóis/administração & dosagem , Levodopa/toxicidade , Oxidopamina/toxicidade , Piperidinas/administração & dosagem , Receptores Histamínicos H3/fisiologia , Animais , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Discinesia Induzida por Medicamentos/metabolismo , Masculino , Ratos , Ratos Wistar , Substância Negra/efeitos dos fármacos , Substância Negra/metabolismoRESUMO
Drug abuse and addiction are overwhelming health problems mainly during adolescence. Based on a previous study of our research group, the rats that received modafinil (MD) during the adolescence showed less preference for amphetamine (AMPH) in adulthood. Our current hypothesis is that MD will show beneficial effects against AMPH preference and abstinence symptoms during adolescence, a critical lifetime period when drug hedonic effects are more pronounced. We investigated the influence of MD pretreatment on AMPH preference in conditioned place preference (CPP) paradigm in adolescent rats and anxiety-like symptoms during drug withdrawal (48â¯h after the last AMPH dose) in elevated plus maze (EPM) task. Besides that, oxidative and molecular status were evaluated in the ventral tegmental area (VTA) and striatum. Our findings showed, as it was expected, that adolescent animals developed AMPH preference together with anxiety-like symptoms during the drug withdrawal while the MD pretreatment prevented those behaviors. Besides promoting benefits on reward parameters, MD was able to preserve VTA and striatum from oxidative damages. This was observed by the increased catalase activity and reduced generation of reactive species and lipid peroxidation, which were inversely modified by AMPH exposure. At molecular level, MD exerted an interesting modulatory activity on the VTA and induced an up-regulation in striatal dopaminergic targets (TH, DAT, D1R and D2R). So far, during the adolescence, MD presented beneficial behavioral outcomes that could be attributed to its modulatory activity on the striatal dopaminergic system in an attempt to maintain the adequate dopamine levels.
Assuntos
Transtornos Relacionados ao Uso de Anfetaminas/tratamento farmacológico , Ansiedade/prevenção & controle , Estimulantes do Sistema Nervoso Central/farmacologia , Modafinila/farmacologia , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Anfetamina/farmacologia , Transtornos Relacionados ao Uso de Anfetaminas/metabolismo , Animais , Ansiedade/etiologia , Ansiedade/metabolismo , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/crescimento & desenvolvimento , Corpo Estriado/metabolismo , Modelos Animais de Doenças , Dopamina/metabolismo , Masculino , Ratos Wistar , Maturidade Sexual , Síndrome de Abstinência a Substâncias/metabolismo , Síndrome de Abstinência a Substâncias/psicologia , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/crescimento & desenvolvimento , Área Tegmentar Ventral/metabolismoRESUMO
Corticotrophin releasing factor (CRF) and its related peptides differentially bind to CRF receptors to modulate stress-related behaviors. CRF receptors comprise two G-protein coupled receptors (GPCR), type-1 CRF receptors (CRF1), and type-2 CRF receptors (CRF2). CRF2 encompasses three spliced variants in humans, alpha (CRF2α), beta (CRF2ß), and gamma (CRF2γ), which differ in their N-terminal extracellular domains and expression patterns. Previously, we showed that CRF2α form a heteromeric protein complex with dopamine D1 receptors (D1R), leading to changes in the signaling of D1R. Based on the high sequence identity between CRF2α and CRF2ß, we hypothesized that CRF2ß also heteromerize with D1R. To test the hypothesis, we compared the expression and localization of both CRF2 isoforms and whether CRF2ß form stable protein complexes with D1R in HEK293 and ATR75 cell lines. We observed that the immunoreactivity for CRF2ß was similar to that of CRF2α in the endoplasmic compartment but significantly higher in the Golgi compartment. Immunoprecipitation analysis showed that CRF2ß forms a heteromeric protein complex with D1R. Furthermore, the protein complex formed by CRF2ß and D1R was stable enough to change the sub-cellular localization of CRF2ß when it was co-expressed with a construct of D1R bearing a nuclear localization signal. Immunofluorescence in A7R5 cells, which endogenously express CRF2ß and D1R, shows significant colocalization of CRF2ß with D1R. In conclusion, our results show that CRF2ß forms a stable heteromeric protein complex with D1R, a potential new therapeutic target in tissues where both receptors are co-expressed, such as the septum in the brain, and heart, kidney, and skeletal muscle in the periphery.
RESUMO
While the role of the ascending dopaminergic system in brain function and dysfunction has been a subject of extensive research, the role of the descending dopaminergic system in spinal cord function and dysfunction is just beginning to be understood. Adenosine plays a key role in the inhibitory control of the ascending dopaminergic system, largely dependent on functional complexes of specific subtypes of adenosine and dopamine receptors. Combining a selective destabilizing peptide strategy with a proximity ligation assay and patch-clamp electrophysiology in slices from male mouse lumbar spinal cord, the present study demonstrates the existence of adenosine A1-dopamine D1 receptor heteromers in the spinal motoneuron by which adenosine tonically inhibits D1 receptor-mediated signaling. A1-D1 receptor heteromers play a significant control of the motoneuron excitability, represent main targets for the excitatory effects of caffeine in the spinal cord and can constitute new targets for the pharmacological therapy after spinal cord injury, motor aging-associated disorders and restless legs syndrome.