RESUMEN
Recent work demonstrated that activation of spinal D1 and D5 dopamine receptors (D1/D5Rs) facilitates non-Hebbian long-term potentiation (LTP) at primary afferent synapses onto spinal projection neurons. However, the cellular localization of the D1/D5Rs driving non-Hebbian LTP in spinal nociceptive circuits remains unknown, and it is also unclear whether D1/D5R signaling must occur concurrently with sensory input in order to promote non-Hebbian LTP at these synapses. Here we investigate these issues using cell-type-selective knockdown of D1Rs or D5Rs from lamina I spinoparabrachial neurons, dorsal root ganglion (DRG) neurons, or astrocytes in adult mice of either sex using Cre recombinase-based genetic strategies. The LTP evoked by low-frequency stimulation of primary afferents in the presence of the selective D1/D5R agonist SKF82958 persisted following the knockdown of D1R or D5R in spinoparabrachial neurons, suggesting that postsynaptic D1/D5R signaling was dispensable for non-Hebbian plasticity at sensory synapses onto these key output neurons of the superficial dorsal horn (SDH). Similarly, the knockdown of D1Rs or D5Rs in DRG neurons failed to influence SKF82958-enabled LTP in lamina I projection neurons. In contrast, SKF82958-induced LTP was suppressed by the knockdown of D1R or D5R in spinal astrocytes. Furthermore, the data indicate that the activation of D1R/D5Rs in spinal astrocytes can either retroactively or proactively drive non-Hebbian LTP in spinoparabrachial neurons. Collectively, these results suggest that dopaminergic signaling in astrocytes can strongly promote activity-dependent LTP in the SDH, which is predicted to significantly enhance the amplification of ascending nociceptive transmission from the spinal cord to the brain.
Asunto(s)
Astrocitos , Potenciación a Largo Plazo , Receptores de Dopamina D1 , Receptores de Dopamina D5 , Sinapsis , Animales , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/genética , Potenciación a Largo Plazo/fisiología , Astrocitos/metabolismo , Astrocitos/fisiología , Ratones , Masculino , Receptores de Dopamina D5/metabolismo , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/genética , Femenino , Sinapsis/fisiología , Sinapsis/metabolismo , Ganglios Espinales/citología , Asta Dorsal de la Médula Espinal/metabolismo , Asta Dorsal de la Médula Espinal/citología , Ratones Transgénicos , Ratones Endogámicos C57BLRESUMEN
Highly correlated firing of primary afferent inputs and lamina I projection neurons evokes synaptic long-term potentiation (LTP), a mechanism by which ascending nociceptive transmission can be amplified at the level of the spinal dorsal horn. However, the degree to which neuromodulatory signaling shapes the temporal window governing spike-timing-dependent plasticity (STDP) at sensory synapses onto projection neurons remains unclear. The present study demonstrates that activation of spinal D1/D5 dopamine receptors (D1/D5Rs) creates a highly permissive environment for the production of LTP in male and female adult mouse spinoparabrachial neurons by promoting non-Hebbian plasticity. Bath application of the mixed D1/D5R agonist SKF82958 unmasked LTP at STDP pairing intervals that normally fail to alter synaptic efficacy. Furthermore, during D1/D5R signaling, action potential discharge in projection neurons became dispensable for LTP generation, and primary afferent stimulation alone was sufficient to induce strengthening of sensory synapses. This non-Hebbian LTP was blocked by the D1/D5R antagonist SCH 39166 or genetic deletion of D5R, and required activation of mGluR5 and intracellular Ca2+ release but was independent of NMDAR activation. D1/D5R-enabled non-Hebbian plasticity was observed across multiple neuronal subpopulations in the superficial dorsal horn but was more prevalent in spinoparabrachial neurons than interneurons. Interestingly, the ability of neonatal tissue damage to promote non-Hebbian LTP in adult projection neurons was not observed in D5R knock-out mice. Collectively, these findings suggest that joint spinal D1/D5R and mGluR5 activation can allow unfettered potentiation of sensory synapses onto the output neurons responsible for conveying pain and itch information to the brain.SIGNIFICANCE STATEMENT Synaptic LTP in spinal projection neurons has been implicated in the generation of chronic pain. Under normal conditions, plasticity at sensory synapses onto adult mouse spinoparabrachial neurons follows strict Hebbian learning rules, requiring coincident presynaptic and postsynaptic firing. Here, we demonstrate that the activation of spinal D1/D5Rs promotes a switch from Hebbian to non-Hebbian LTP so that primary afferent stimulation alone is sufficient to evoke LTP in the absence of action potential discharge in projection neurons, which required joint activation of mGluR5 and intracellular Ca2+ release but not NMDARs. These results suggest that D1/D5Rs cooperate with mGluR5 receptors in the spinal dorsal horn to powerfully influence the amplification of ascending nociceptive transmission to the brain.
Asunto(s)
Potenciación a Largo Plazo/efectos de los fármacos , Neuronas/efectos de los fármacos , Receptor del Glutamato Metabotropico 5/metabolismo , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Asta Dorsal de la Médula Espinal/efectos de los fármacos , Sinapsis/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Animales , Benzazepinas/farmacología , Calcio/metabolismo , Agonistas de Dopamina/farmacología , Femenino , Masculino , Ratones , Ratones Noqueados , Neuronas/metabolismo , Receptores de Dopamina D1/genética , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/genética , Receptores de Dopamina D5/metabolismo , Asta Dorsal de la Médula Espinal/metabolismo , Sinapsis/metabolismoRESUMEN
Decades of research have highlighted the importance of optimal stimulation of cortical dopaminergic receptors, particularly the D1R receptor (D1R), for prefrontal-mediated cognition. This mechanism is particularly relevant to the cognitive deficits in schizophrenia, given the abnormalities in cortical dopamine (DA) neurotransmission and in the expression of D1R. Despite the critical need for D1R-based therapeutics, many factors have complicated their development and prevented this important therapeutic target from being adequately interrogated. Challenges include determination of the optimal level of D1R stimulation needed to improve cognitive performance, especially when D1R expression levels, affinity states, DA levels, and the resulting D1R occupancy by DA, are not clearly known in schizophrenia, and may display great interindividual and intraindividual variability related to cognitive states and other physiological variables. These directly affect the selection of the level of stimulation necessary to correct the underlying neurobiology. The optimal mechanism for stimulation is also unknown and could include partial or full agonism, biased agonism, or positive allosteric modulation. Furthermore, the development of D1R targeting drugs has been complicated by complexities in extrapolating from in vitro affinity determinations to in vivo use. Prior D1R-targeted drugs have been unsuccessful due to poor bioavailability, pharmacokinetics, and insufficient target engagement at tolerable doses. Newer drugs have recently become available, and these must be tested in the context of carefully designed paradigms that address methodological challenges. In this paper, we discuss how a better understanding of these challenges has shaped our proposed experimental design for testing a new D1R/D5R partial agonist, PF-06412562, renamed CVL-562.
Asunto(s)
Disfunción Cognitiva/tratamiento farmacológico , Agonistas de Dopamina/farmacología , Desarrollo de Medicamentos , Receptores de Dopamina D1/agonistas , Esquizofrenia/tratamiento farmacológico , Adulto , Disfunción Cognitiva/etiología , Disfunción Cognitiva/metabolismo , Agonistas de Dopamina/administración & dosificación , Humanos , Receptores de Dopamina D5/agonistas , Esquizofrenia/complicaciones , Esquizofrenia/metabolismoRESUMEN
Acute stressors are recurrent in multiple species' lives and can facilitate or impair cognition. The use of zebrafish (Danio rerio) as a translational species to understand the mechanisms by which stress induces different behavioral phenotypes has been widely studied. Two acute stressors are recognized when using this species: (1) conspecific alarm substance (CAS); and (2) net chasing. Here, we tested if CAS or net chasing would affect working memory and cognitive flexibility by testing performance in the FMP Y-maze after exposure to stress. We observed that CAS altered zebrafish behavioral phenotypes by increasing repetitive behavior; meanwhile, animals showed different patterns of repetitive behavior when exposed to net chasing, depending on the chasing direction. Because D1 receptors were previously studied as a potential mechanism underlying stress responses in different species, here, we pretreated fish with a D1/D5 agonist (SKF-38393) to assess whether this system plays a role in repetitive behavior in the FMP Y-maze. The pretreatment with D1/D5 agonist significantly decreased repetitive behavior in CAS exposed animals, and cortisol levels for both stressed groups, suggesting that the dopaminergic system plays an important role in zebrafish stress-related responses.
Asunto(s)
Conducta Animal/fisiología , Cognición/fisiología , Hidrocortisona/metabolismo , Memoria a Corto Plazo/fisiología , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Estrés Psicológico/metabolismo , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/farmacología , Animales , Conducta Animal/efectos de los fármacos , Cognición/efectos de los fármacos , Agonistas de Dopamina/farmacología , Aprendizaje por Laberinto/efectos de los fármacos , Aprendizaje por Laberinto/fisiología , Memoria a Corto Plazo/efectos de los fármacos , Feromonas , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Conducta Estereotipada/efectos de los fármacos , Conducta Estereotipada/fisiología , Pez CebraRESUMEN
Recent findings from this laboratory demonstrate that ethanol reduces the intrinsic excitability of orbitofrontal cortex (OFC) neurons via activation of strychnine-sensitive glycine receptors. Although the mechanism linking ethanol to the release of glycine is currently unknown, astrocytes are a source of neurotransmitters including glycine and activation of dopamine D1-like receptors has been reported to enhance extracellular levels of glycine via a functional reversal of the astrocytic glycine transporter GlyT1. We recently reported that like ethanol, dopamine or a D1/D5 receptor agonist increases a tonic current in lateral OFC (lOFC) neurons. Therefore, in this study, we used whole-cell patch-clamp electrophysiology to examine whether ethanol inhibition of OFC spiking involves the release of glycine from astrocytes and whether this release is dopamine receptor dependent. Ethanol, applied acutely, decreased spiking of lOFC neurons and this effect was blocked by antagonists of GlyT1, the norepinephrine transporter or D1-like but not D2-like receptors. Ethanol enhanced the tonic current of OFC neurons and occluded the effect of dopamine suggesting that ethanol and dopamine may share a common pathway. Altering astrocyte function by suppressing intracellular astrocytic calcium signaling or blocking the astrocyte-specific Kir4.1 potassium channels reduced but did not completely abolish ethanol inhibition of OFC neuron firing. However, when both astrocytic calcium signaling and Kir4.1 channels were inhibited, ethanol had no effect on firing. Ethanol inhibition was also prevented by inhibitors of phospholipase C and conventional isoforms of protein kinase C (cPKC) previously shown to block D1R-induced GlyT1 reversal and PKC inhibition of Kir4.1 channels. Finally, the membrane potential of OFC astrocytes was depolarized by bath application of a Kir4.1 blocker, a D1 agonist or ethanol and ethanol effect was blocked by a D1 antagonist. Together, these findings suggest that acute ethanol inhibits OFC neuron excitability via a D1 receptor-mediated dysregulation of astrocytic glycine transport.
Asunto(s)
Astrocitos/metabolismo , Etanol/toxicidad , Glicina/metabolismo , Corteza Prefrontal/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Animales , Astrocitos/efectos de los fármacos , Dopaminérgicos/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Técnicas de Cultivo de Órganos , Corteza Prefrontal/efectos de los fármacos , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/antagonistas & inhibidores , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/antagonistas & inhibidoresRESUMEN
BACKGROUND: Current drug treatments have little efficacy in advanced-to-end-stage Parkinson's disease (advPD), yet there are no reports of interventional trials in advPD. D1 dopamine agonists have the potential to provide benefit. OBJECTIVE: To determine the feasibility and safety of the selective D1/D5 dopamine partial agonist PF 06412562 in advPD. METHODS: A two-week, randomized, double blind, crossover phase Ib study in advPD patients compared standard-of-care (SoC) carbidopa/levodopa with PF 06412562. Each week, there was a Day 1 baseline evaluation with overnight levodopa washout, then treatment on Days 2 and 3 with either SoC or PF-06412562 (split dose 25â+â20âmg), followed by discharge on Day 4. Primary endpoints were safety and tolerability. Secondary endpoints were global clinical impression of change (GCI-C) rated by clinicians and caregivers. RESULTS: Eight advPD patients and their caregivers consented to participate and six were randomized (average disease duration: 22ây). None withdrew voluntarily. One participant with baseline Day 1 dehydration, pre-renal kidney injury, and autonomic dysfunction experienced symptomatic and serious hypotension after receiving PF-06412562 in Week 1 and was discontinued from the study. All other adverse events were rated mild (PF-06412562: nâ=â1, SoC: nâ=â0), moderate (PF-06412562: nâ=â1, SoC: nâ=â1), or severe but non-serious (PF-06412562: nâ=â3, SoC: nâ=â2). No clinically meaningful laboratory changes were observed. Among the five participants who completed the study, GCI-C favored PF-06412562 in two per clinicians' and four participants per caregivers' rating. CONCLUSION: PF-06412562 was tolerated in advPD patients. This study provides the feasibility for future safety and efficacy studies in this population with unmet needs.
Asunto(s)
Carbidopa/farmacología , Agonistas de Dopamina/farmacología , Levodopa/farmacología , Enfermedad de Parkinson/tratamiento farmacológico , Receptores de Dopamina D1/agonistas , Anciano , Carbidopa/administración & dosificación , Carbidopa/efectos adversos , Estudios Cruzados , Agonistas de Dopamina/administración & dosificación , Agonistas de Dopamina/efectos adversos , Método Doble Ciego , Combinación de Medicamentos , Estudios de Factibilidad , Femenino , Humanos , Levodopa/administración & dosificación , Levodopa/efectos adversos , Masculino , Persona de Mediana Edad , Evaluación de Resultado en la Atención de Salud , Receptores de Dopamina D5/agonistas , Índice de Severidad de la EnfermedadRESUMEN
New aporphines containing C10 nitrogen substituents (viz. nitro, aniline or amide moieties), were synthesized and evaluated for affinity at human serotonin 5-HT1A and 5-HT2A receptors and at human dopamine D1, D2 and D5 receptors. Two series of analogs were investigated: series A which contain a sole C10 nitrogen substituent on the tetracyclic aporphine core and series B which are 1,2,10-trisubstituted aporphines. Remarkably, compounds from both series lacked affinity for the D5 receptor, thus attaining D1 versus D5 selectivity. Compound 20c was the most potent D1 ligand identified. Docking studies at D1 and D5 receptors indicate that the binding mode of 20c at the D1 receptor allows for stronger hydrophobic contacts, (primarily with Phe residues) as compared to the D5 receptor, accounting for its D1 versus D5 selectivity. Considering the lack of affinity for the D5 receptor (and low affinity at other receptors tested), compound 20c represents an interesting starting point for further structural diversification of aporphines as sub-type selective D1 receptor tools.
Asunto(s)
Aporfinas/farmacología , Agonistas de Dopamina/farmacología , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Aporfinas/química , Agonistas de Dopamina/química , Relación Dosis-Respuesta a Droga , Humanos , Ligandos , Simulación del Acoplamiento Molecular , Estructura Molecular , Relación Estructura-ActividadRESUMEN
BACKGROUND: Dopamine D1 receptor signaling plays key roles in core domains of neural function, including cognition and reward processing; however, many questions remain about the functions of circuits modulated by dopamine D1 receptor, largely because clinically viable, selective agonists have yet to be tested in humans. METHODS: Using a novel, exploratory neurofunctional domains study design, we assessed the safety, tolerability, pharmacodynamics, and pharmacokinetics of PF-06412562, a selective D1/D5R partial agonist, in healthy male volunteers who met prespecified criteria for low working memory capacity. Functional magnetic resonance imaging, electrophysiologic endpoints, and behavioral paradigms were used to assess working memory, executive function, and motivation/reward processing following multiple-dose administration of PF-06412562. A total of 77 patients were assigned PF-06412562 (3 mg twice daily and 15 mg twice daily) or placebo administered for 5 to 7 days. Due to the exploratory nature of the study, it was neither powered for any specific treatment effect nor corrected for multiple comparisons. RESULTS: Nominally significant improvements from baseline in cognitive endpoints were observed in all 3 groups; however, improvements in PF-06412562-treated patients were less than in placebo-treated participants. Motivation/reward processing endpoints were variable. PF-06412562 was safe and well tolerated, with no serious adverse events, severe adverse events, or adverse events leading to dose reduction or temporary discontinuation except for 1 permanent discontinuation due to increased orthostatic heart rate. CONCLUSIONS: PF-06412562, in the dose range and patient population explored in this study, did not improve cognitive function or motivation/reward processing more than placebo over the 5- to 7-day treatment period. CLINICALTRIALS.GOV IDENTIFIER: NCT02306876.
Asunto(s)
Encéfalo/efectos de los fármacos , Cognición/efectos de los fármacos , Agonistas de Dopamina/administración & dosificación , Memoria a Corto Plazo/efectos de los fármacos , Motivación/efectos de los fármacos , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Adolescente , Adulto , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Agonistas de Dopamina/efectos adversos , Agonistas de Dopamina/farmacocinética , Método Doble Ciego , Esquema de Medicación , Agonismo Parcial de Drogas , Función Ejecutiva/efectos de los fármacos , Voluntarios Sanos , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Adulto JovenRESUMEN
BACKGROUND: PF-06412562 is an orally bioavailable, selective dopamine D1/D5 receptor partial agonist with a non-catechol structure under evaluation for treatment of cognitive impairment in schizophrenia. AIMS: This randomized, double-blind, placebo-controlled, parallel-group, Phase 1b study examined the pharmacokinetics and pharmacodynamics of three doses of PF-06412562 (3 mg, 9 mg, and 45 mg twice daily) over 15 days in patients with schizophrenia receiving antipsychotics. METHODS: Primary endpoints included adjunctive safety/tolerability and effects on MATRICS Consensus Cognitive Battery Working Memory domain and reward processing (Monetary Incentive Delay) tasks. Exploratory endpoints included other behavioral/neurophysiological tasks, including the N-back task. RESULTS: Among 95 subjects (78% male; mean age 34.8 years), baseline characteristics were similar across groups. The MATRICS Consensus Cognitive Battery Working Memory composite change from baseline on Day 13 improved in all groups, the smallest improvement was observed in the 45 mg group and was significantly smaller than that in the placebo group (two-sided p=0.038). For the Monetary Incentive Delay task (change from baseline in blood-oxygen-level-dependent functional magnetic resonance imaging activation in anterior ventral striatum for the contrast of cue gain>cue no gain on Day 15), no PF-06412562 dose was significantly different from placebo. No doses of PF-06412562 showed a significant difference on two-back task accuracy versus placebo. CONCLUSIONS: Adjunctive treatment with PF-06412562 was safe and well tolerated in patients with schizophrenia. PF-06412562 failed to show clinical benefit relative to placebo on assessments of cognition or reward processing in symptomatically stable patients over a 15-day treatment period. Numerous limitations due to the safety study design warrant further efficacy evaluation for this drug mechanism.
Asunto(s)
Antipsicóticos/farmacología , Disfunción Cognitiva/tratamiento farmacológico , Agonistas de Dopamina/farmacocinética , Receptores de Dopamina D1/agonistas , Esquizofrenia/tratamiento farmacológico , Adulto , Disfunción Cognitiva/etiología , Agonistas de Dopamina/administración & dosificación , Método Doble Ciego , Quimioterapia Combinada , Femenino , Humanos , Masculino , Memoria a Corto Plazo/efectos de los fármacos , Motivación/efectos de los fármacos , Receptores de Dopamina D5/agonistas , Recompensa , Esquizofrenia/complicaciones , Resultado del TratamientoRESUMEN
fMRI was used to study late effects of dopamine D1/5 receptor activation on hippocampal signal processing and signal propagation to several target regions. The dopamine D1/5 receptor agonists SKF83959 and SKF38393 were intraperitoneally applied without, immediately before or 7 days after electrical stimulation of the right perforant pathway with bursts of high-frequency pulses. Control animals received a 0.9% NaCl solution. One day after D1/5 receptor activation, the perforant pathway was stimulated and the induced BOLD responses in the right hippocampus and its target regions, left hippocampus (l-HC) and medial prefrontal cortex (mPFC), were measured. Depending on the temporal relation between dopamine receptor activation and the first perforant pathway stimulation the induced BOLD response pattern differed. When applied without concurrent perforant pathway stimulation, the agonists caused region-selective increases in the induced BOLD responses: the effect of SKF83959 was evident in the mPFC whereas that of SKF38393 was confined to the l-HC. When applied in conjunction with perforant pathway stimulation, either agonist caused increased BOLD responses in both regions. In contrast, when applied 7 days after perforant pathway stimulation, neither SKF83959 nor SKF38393 modified the BOLD responses in the mPFC or l-HC 1day later. These findings suggest that (i) activation of dopamine D1/5 receptors alone is sufficient to modify stimulus-induced BOLD responses in target regions of the right hippocampus 24h later, and (ii), the history of previous stimulations crucially affects the impact of dopamine receptor activation on stimulus-induced BOLD responses.
Asunto(s)
Hipocampo/fisiología , Receptores de Dopamina D1/fisiología , Receptores de Dopamina D5/fisiología , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/administración & dosificación , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/análogos & derivados , Animales , Mapeo Encefálico , Agonistas de Dopamina/administración & dosificación , Estimulación Eléctrica , Hipocampo/efectos de los fármacos , Imagen por Resonancia Magnética , Masculino , Vía Perforante/fisiología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/fisiología , Ratas Wistar , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistasRESUMEN
Dopamine is known to play an important role in the pathophysiological process of myopia development relevant to the ambient lighting, but it is still poorly understood about how lighting regulates dopamine and its interaction with dopamine receptors to mediate the pathogenic signal transduction leading to alterations of ocular globe and the pathogenesis of myopia. Many studies have highlighted changes of ocular dopamine amount in response to different lighting conditions, but little attention has been paid to the dopamine receptors during these processes. Here we examined the effects of different lighting exposures on the expression of dopamine receptors in rat R28 retinal precursor cells. R28 cells normally grown in dark were exposed to a low (10 lux) or high (500 lux) intensity of a source of LED white light (5000 K-6000 K) for 12 h and total RNA was isolated either immediately or after certain time continuous growing in dark. Both conventional and real-time RT-PCR were performed to determine the expression of all five different dopamine receptors in cells after treatments. While the transcripts of dopamine D2, D3, and D4 receptors were not detected in the total RNA preparations of all the cells, those of D1 and D5 receptors (DRD1 and DRD5) were induced by lighting in contrast to the dark control. Elevated levels of DRD1 and DRD5 mRNA returned back close to the original levels once the cells were maintained in dark after light exposures. Immunofluorescence microscopy using a specific antibody confirmed an increase in the immunoreactivity of DRD1 in the cells exposed to 500 lux lighting versus dark control. Notably, treatments of R28 cells with nanomolar dosages of dopamine (0-500 nM) directly downregulated expression of both DRD1 and DRD5, whereas haloperidol (0-50 nM), a DRD2 antagonist, significantly induced expression of DRD1. These results suggest that dopamine receptors in the retinal cells might actively respond to the environmental lighting to act as an important player in the activation of the dopaminergic system in the ocular structures relevant to the lighting-induced pathogenic development of myopia.
Asunto(s)
Células Epiteliales/efectos de la radiación , Fototransducción , Receptores de Dopamina D1/genética , Receptores de Dopamina D5/genética , Retina/efectos de la radiación , Animales , Línea Celular , Dopamina/farmacología , Células Epiteliales/citología , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Regulación de la Expresión Génica , Haloperidol/farmacología , Luz , Ratas , Ratas Sprague-Dawley , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/antagonistas & inhibidores , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/antagonistas & inhibidores , Receptores de Dopamina D5/metabolismo , Retina/citología , Retina/efectos de los fármacos , Retina/metabolismoRESUMEN
Dopaminergic neurotransmission modulates and influences hippocampal CA1 synaptic plasticity, learning and long-term memory mechanisms. Investigating the mechanisms involved in the slow-onset potentiation induced by the dopamine D1/D5 receptor agonists in hippocampal CA1 region, we have reported recently that it could play a role in regulating synaptic cooperation and competition. We have also shown that a sustained activation of MEK/MAP kinase pathway was involved in the maintenance of this long-lasting potentiation (Shivarama Shetty, Gopinadhan, & Sajikumar, 2016). However, the molecular aspects of the induction of dopaminergic slow-onset potentiation are not known. Here, we investigated the involvement of MEK/MAPK pathway and Ca2+-calmodulin-dependent protein kinases (CaMKII and CaMKIV) in the induction and maintenance phases of the D1/D5 receptor-mediated slow-onset potentiation. We report differential involvement of these kinases in a dose-dependent manner wherein at weaker levels of dopaminergic activation, both CaMKII and MEK1/2 activation is necessary for the establishment of potentiation and with sufficiently stronger dopaminergic activation, the role of CaMKII becomes dispensable whereas MEK activation remains crucial for the long-lasting potentiation. The results are interesting in view of the involvement of the hippocampal dopaminergic system in a variety of cognitive abilities including memory formation and also in neurological diseases such as Alzheimer's disease and Parkinson's disease.
Asunto(s)
Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Proteína Quinasa Tipo 4 Dependiente de Calcio Calmodulina/metabolismo , Hipocampo/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Plasticidad Neuronal/fisiología , Células Piramidales/metabolismo , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/metabolismo , Animales , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/antagonistas & inhibidores , Proteína Quinasa Tipo 4 Dependiente de Calcio Calmodulina/antagonistas & inhibidores , Agonistas de Dopamina/farmacología , Inhibidores Enzimáticos/farmacología , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Potenciales Postsinápticos Excitadores/fisiología , Hipocampo/efectos de los fármacos , Masculino , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Plasticidad Neuronal/efectos de los fármacos , Células Piramidales/efectos de los fármacos , Ratas , Ratas Wistar , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiologíaRESUMEN
Dopamine signaling is involved in a variety of neurobiological processes that contribute to learning and memory. D1-like dopamine receptors (including D1 and D5 receptors) are thought to be involved in memory and reward processes, but pharmacological approaches have been limited in their ability to distinguish between D1 and D5 receptors. Here, we examine the effects of a specific knockout of D1 receptors in associative learning tasks involving aversive (shock) or appetitive (cocaine) unconditioned stimuli. We find that D1 knockout mice show similar levels of cued and contextual fear conditioning to WT controls following conditioning protocols involving one, two, or four shocks. D1 knockout mice show increased generalization of fear conditioning and extinction across contexts, revealed as increased freezing to a novel context following conditioning and decreased freezing to an extinguished cue during a contextual renewal test. Further, D1 knockout mice show mild enhancements in extinction following an injection of SKF81297, a D1/D5 receptor agonist, suggesting a role for D5 receptors in extinction enhancements induced by nonspecific pharmacological agonists. Finally, although D1 knockout mice show decreased locomotion induced by cocaine, they are able to form a cocaine-induced conditioned place preference. We discuss these findings in terms of the role of dopamine D1 receptors in general learning and memory processes.
Asunto(s)
Conducta Animal/fisiología , Condicionamiento Clásico/fisiología , Extinción Psicológica/fisiología , Miedo/fisiología , Generalización Psicológica/fisiología , Receptores de Dopamina D1/fisiología , Receptores de Dopamina D5/fisiología , Recompensa , Animales , Conducta Animal/efectos de los fármacos , Benzazepinas/administración & dosificación , Benzazepinas/farmacología , Cocaína/administración & dosificación , Cocaína/farmacología , Agonistas de Dopamina/administración & dosificación , Agonistas de Dopamina/farmacología , Inhibidores de Captación de Dopamina/administración & dosificación , Inhibidores de Captación de Dopamina/farmacología , Femenino , Masculino , Ratones , Ratones Noqueados , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistasRESUMEN
Dopamine is critical for many processes that drive learning and memory, including motivation, prediction error, incentive salience, memory consolidation, and response output. Theories of dopamine's function in these processes have, for the most part, been developed from behavioral approaches that examine learning mechanisms in appetitive tasks. A parallel and growing literature indicates that dopamine signaling is involved in consolidation of memories into stable representations in aversive tasks such as fear conditioning. Relatively little is known about how dopamine may modulate memories that form during extinction, when organisms learn that the relation between previously associated events is severed. We investigated whether fear and reward extinction share common mechanisms that could be enhanced with dopamine D1/5 receptor activation. Pharmacological activation of dopamine D1/5 receptors (with SKF 81297) enhanced extinction of both cued and contextual fear. These effects also occurred in the extinction of cocaine-induced conditioned place preference, suggesting that the observed effects on extinction were not specific to a particular type of procedure (aversive or appetitive). A cAMP/PKA biased D1 agonist (SKF 83959) did not affect fear extinction, whereas a broadly efficacious D1 agonist (SKF 83822) promoted fear extinction. Together, these findings show that dopamine D1/5 receptor activation is a target for the enhancement of fear or reward extinction.
Asunto(s)
Extinción Psicológica/fisiología , Miedo/fisiología , Receptores de Dopamina D1/fisiología , Receptores de Dopamina D5/fisiología , Recompensa , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/administración & dosificación , 2,3,4,5-Tetrahidro-7,8-dihidroxi-1-fenil-1H-3-benzazepina/análogos & derivados , Animales , Benzazepinas/administración & dosificación , Cocaína/administración & dosificación , Condicionamiento Clásico/efectos de los fármacos , AMP Cíclico/metabolismo , Extinción Psicológica/efectos de los fármacos , Miedo/efectos de los fármacos , Masculino , Ratones Endogámicos C57BL , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , beta-Arrestinas/metabolismoRESUMEN
In this study, a high throughput screening system was set up to identify D5 receptor agonists-027075. Then, a series of behavior tests were used to evaluate the beneficial effects of 027075 in Aß1-42-induced mice model including morris water maze, passive avoidance, active avoidance, open field and step-down test. The neuroprotective effect of 027075 was assessed by a high content screening in vitro. In behavior tests, the cognitive function impairment caused by Aß1-42 was significantly ameliorated by 027075 in a dose-dependent manner. 027075 (8 mg/kg) significantly prolonged the time spent in the target quadrant when compared to the model group in morris water maze test. The latency was significantly increased and the number of errors was decreased in both passives avoidance task and step down test when compared to the model group. In active avoidance and open field test, latency, stimulation time, number of errors were significantly reduced, while number of avoidance and line crossing and central distance were increased by 027075 (8 mg/kg). All the results above was significantly reversed by 027075-H + SCH39166 (5 mg/kg) when compared to 027075-H (8 mg/kg). The neuroprotective effect of 027075 was demonstrated by promotion of cell differentiation and extension of neurite length. But the effects were abrogated by the specific D1/D5 antagonist, SCH39166. These results indicate that D5 receptor might be used as an ideal target for the treatment of AD and its agonists might become a new AD drugs in the future.
Asunto(s)
Enfermedad de Alzheimer/prevención & control , Benzodioxoles/administración & dosificación , Benzodioxoles/análisis , Cognición/efectos de los fármacos , Neurogénesis/efectos de los fármacos , Ftalazinas/administración & dosificación , Ftalazinas/análisis , Receptores de Dopamina D5/agonistas , Recuperación de la Función/efectos de los fármacos , Acetilcolinesterasa/metabolismo , Enfermedad de Alzheimer/inducido químicamente , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/psicología , Péptidos beta-Amiloides/toxicidad , Animales , Apoptosis/efectos de los fármacos , Benzodioxoles/farmacocinética , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Ensayos Analíticos de Alto Rendimiento , Aprendizaje/efectos de los fármacos , Masculino , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Ratones , Ratones Endogámicos ICR , Neuronas/efectos de los fármacos , Neuronas/fisiología , Fragmentos de Péptidos/toxicidad , Ftalazinas/farmacocinética , Proteínas tau/metabolismoRESUMEN
Synaptic cooperation and competition are important components of synaptic plasticity that tune synapses for the formation of associative long-term plasticity, a cellular correlate of associative long-term memory. We have recently reported that coincidental activation of weak synapses within the vicinity of potentiated synapses will alter the cooperative state of synapses to a competitive state thus leading to the slow decay of long-term plasticity, but the molecular mechanism underlying this is still unknown. Here, using acute hippocampal slices of rats, we have examined how increasing extracellular dopamine concentrations interact and/or affect electrically induced long-term potentiation (LTP) in the neighboring synapses. We demonstrate that D1/D5-receptor-mediated potentiation at the CA1 Schaffer collateral synapses differentially regulates synaptic co-operation and competition. Further investigating the molecular players involved, we reveal an important role for extracellular signal-regulated kinases-1 and 2 (ERK1/2) as signal integrators and dose-sensors. Interestingly, a sustained activation of ERK1/2 pathway seems to be involved in the differential regulation of synaptic associativity. The concentration-dependent effects of the modulatory transmitter, as demonstrated for dopaminergic signaling in the present study, might offer additional computational power by fine tuning synaptic associativity processes for establishing long-term associative memory in neural networks.
Asunto(s)
Región CA1 Hipocampal/fisiología , Sistema de Señalización de MAP Quinasas/fisiología , Células Piramidales/fisiología , Receptores de Dopamina D1/fisiología , Receptores de Dopamina D5/fisiología , Sinapsis/fisiología , Animales , Región CA1 Hipocampal/citología , Región CA1 Hipocampal/efectos de los fármacos , Agonistas de Dopamina/farmacología , Relación Dosis-Respuesta a Droga , Activación Enzimática/efectos de los fármacos , Activación Enzimática/fisiología , Masculino , Plasticidad Neuronal/efectos de los fármacos , Plasticidad Neuronal/fisiología , Técnicas de Cultivo de Órganos , Células Piramidales/efectos de los fármacos , Ratas , Ratas Wistar , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D5/agonistas , Sinapsis/efectos de los fármacosRESUMEN
The mechanisms that lead to the maintenance of chronic pain states are poorly understood, but their elucidation could lead to new insights into how pain becomes chronic and how it can potentially be reversed. We investigated the role of spinal dorsal horn neurons and descending circuitry in plasticity mediating a transition to pathological pain plasticity suggesting the presence of a chronic pain state using hyperalgesic priming. We found that when dorsal horn neurokinin 1 receptor-positive neurons or descending serotonergic neurons were ablated before hyperalgesic priming, IL-6- and carrageenan-induced mechanical hypersensitivity was impaired, and subsequent prostaglandin E2 (PGE2) response was blunted. However, when these neurons were lesioned after the induction of priming, they had no effect on the PGE2 response, reflecting differential mechanisms driving plasticity in a primed state. In stark contrast, animals with a spinally applied dopaminergic lesion showed intact IL-6- and carrageenan-induced mechanical hypersensitivity, but the subsequent PGE2 injection failed to cause mechanical hypersensitivity. Moreover, ablating spinally projecting dopaminergic neurons after the resolution of the IL-6- or carrageenan-induced response also reversed the maintenance of priming as assessed through mechanical hypersensitivity and the mouse grimace scale. Pharmacological antagonism of spinal dopamine D1/D5 receptors reversed priming, whereas D1/D5 agonists induced mechanical hypersensitivity exclusively in primed mice. Strikingly, engagement of D1/D5 coupled with anisomycin in primed animals reversed a chronic pain state, consistent with reconsolidation-like effects in the spinal dorsal horn. These findings demonstrate a novel role for descending dopaminergic neurons in the maintenance of pathological pain plasticity.
Asunto(s)
Neuronas Dopaminérgicas/fisiología , Células del Asta Posterior/fisiología , Receptores de Dopamina D1/fisiología , Receptores de Dopamina D5/fisiología , Receptores de Neuroquinina-1/fisiología , Animales , Benzazepinas/farmacología , Carragenina/farmacología , Dinoprostona/metabolismo , Dinoprostona/farmacología , Neuronas Dopaminérgicas/efectos de los fármacos , Hiperalgesia/inducido químicamente , Interleucina-6/farmacología , Masculino , Ratones , Células del Asta Posterior/efectos de los fármacos , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/antagonistas & inhibidores , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/antagonistas & inhibidores , Neuronas Serotoninérgicas/fisiología , Sulpirida/farmacologíaRESUMEN
The recent electrophysiological characterization of TH-expressing GABAergic interneurons (THINs) in the neostriatum revealed an unexpected degree of diversity of interneurons in this brain area (Ibáñez-Sandoval et al., 2010, Unal et al., 2011, 2015). Despite being relatively few in number, THINs may play a significant role in transmitting and distributing extra- and intrastriatal neuromodulatory signals in the striatal circuitry. Here we investigated the dopaminergic and cholinergic regulation of THINs in vitro. We found that the dominant effect of dopamine was a dramatic enhancement of the ability of THINs to generate long-lasting depolarizing plateau potentials (PPs). Interestingly, the same effect could also be elicited by amphetamine-induced release of endogenous dopamine suggesting that THINs may exhibit similar responses to changes in extracellular dopamine concentration in vivo. The enhancement of PPs in THINs is perhaps the most pronounced effect of dopamine on the intrinsic excitability of neostriatal neurons described to date. Further, we demonstrate that all subtypes of THINSs tested also express nicotinic cholinergic receptors. All THIS responded, albeit differentially, with depolarization, PPs and spiking to brief application of nicotinic agonists. Powerful modulation of the nonlinear integrative properties of THINs by dopamine and the direct depolarization of these neurons by acetylcholine may play important roles in mediating the effects of these neuromodulators in the neostriatum with potentially important implications for understanding the mechanisms of neuropsychiatric disorders affecting the basal ganglia.
Asunto(s)
Acetilcolina/metabolismo , Dopamina/metabolismo , Interneuronas/fisiología , Neostriado/fisiología , Tirosina 3-Monooxigenasa/metabolismo , Animales , Estimulación Eléctrica , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Interneuronas/citología , Interneuronas/efectos de los fármacos , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Ratones Transgénicos , Neostriado/citología , Neostriado/efectos de los fármacos , Agonistas Nicotínicos/farmacología , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/metabolismo , Receptores Nicotínicos/metabolismo , Técnicas de Cultivo de Tejidos , Tirosina 3-Monooxigenasa/genéticaRESUMEN
The D1 dopamine receptor (D1R) has been implicated in numerous neuropsychiatric disorders, and D1R-selective ligands have potential as therapeutic agents. Previous studies have identified substituted benzazepines as D1R-selective agonists, but the in vivo effects of these compounds have not correlated well with their in vitro pharmacological activities. A series of substituted benzazepines, and structurally dissimilar D1R-selective agonists, were tested for their functional effects on D1R-mediated cAMP accumulation, D1R-promoted ß-arrestin recruitment, and D1R internalization using live cell functional assays. All compounds tested elicited an increase in the level of cAMP accumulation, albeit with a range of efficacies. However, when the compounds were evaluated for ß-arrestin recruitment, a subset of substituted benzazepines, SKF83959, SKF38393, SKF82957, SKF77434, and SKF75670, failed to activate this pathway, whereas the others showed similar activation efficacies as seen with cAMP accumulation. When tested as antagonists, the five biased compounds all inhibited dopamine-stimulated ß-arrestin recruitment. Further, D1R internalization assays revealed a corroborating pattern of activity in that the G protein-biased compounds failed to promote D1R internalization. Interestingly, the biased signaling was unique for the D1R, as the same compounds were agonists of the related D5 dopamine receptor (D5R), but revealed no signaling bias. We have identified a group of substituted benzazepine ligands that are agonists at D1R-mediated G protein signaling, but antagonists of D1R recruitment of ß-arrestin, and also devoid of agonist-induced receptor endocytosis. These data may be useful for interpreting the contrasting effects of these compounds in vitro versus in vivo, and also for the understanding of pathway-selective signaling of the D1R.
Asunto(s)
Arrestinas/metabolismo , Benzazepinas/farmacología , Agonistas de Dopamina/farmacología , Proteínas de Unión al GTP/metabolismo , Receptores de Dopamina D1/agonistas , Receptores de Dopamina D1/metabolismo , Animales , Benzazepinas/química , Células CHO , Línea Celular Tumoral , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Cricetulus , AMP Cíclico/metabolismo , Agonistas de Dopamina/química , Relación Dosis-Respuesta a Droga , Células HEK293 , Humanos , Estructura Molecular , Ensayo de Unión Radioligante , Receptores de Dopamina D1/genética , Receptores de Dopamina D5/agonistas , Receptores de Dopamina D5/genética , Receptores de Dopamina D5/metabolismo , Transfección , beta-ArrestinasRESUMEN
BACKGROUND: SKF83959 stimulates the phospholipase Cß/inositol phosphate 3 pathway, resulting in the activation of Ca(2+)/calmodulin-dependent kinase IIα, which affects the synthesis of brain-derived neurotrophic factor, a neurotrophic factor critical for the pathophysiology of depression. Previous reports showed that SKF83959 elicited antidepressant activity in the forced swim test and tail suspension test as a novel triple reuptake inhibitor. However, there are no studies showing the effects of SKF83959 in a chronic stress model of depression and the role of phospholipase C/inositol phosphate 3/calmodulin-dependent kinase IIα/brain-derived neurotrophic factor pathway in SKF83959-mediated antidepressant effects. METHODS: In this study, SKF83959 was firstly investigated in the chronic social defeat stress model of depression. The changes in hippocampal neurogenesis, dendrite spine density, and brain-derived neurotrophic factor signaling pathway after chronic social defeat stress and SKF83959 treatment were then investigated. Pharmacological inhibitors and small interfering RNA/short hairpin RNA methods were further used to explore the antidepressive mechanisms of SKF83959. RESULTS: We found that SKF83959 produced antidepressant effects in the chronic social defeat stress model and also restored the chronic social defeat stress-induced decrease in hippocampal brain-derived neurotrophic factor signaling pathway, dendritic spine density, and neurogenesis. By using various inhibitors and siRNA/shRNA methods, we further demonstrated that the hippocampal dopamine D5 receptor, phospholipase C/inositol phosphate 3/ calmodulin-dependent kinase IIα pathway, and brain-derived neurotrophic factor system are all necessary for the SKF83959 effects. CONCLUSION: These results suggest that SKF83959 can be developed as a novel antidepressant and produces antidepressant effects via the hippocampal D5/ phospholipase C/inositol phosphate 3/calmodulin-dependent kinase IIα/brain-derived neurotrophic factor pathway.