RESUMO
Fear learning is essential to survival, but traumatic events may lead to abnormal fear consolidation and overgeneralization, triggering fear responses in safe environments, as occurs in post-traumatic stress disorder (PTSD). Adenosine A2A receptors (A2AR) control emotional memory and fear conditioning, but it is not known if they affect the consolidation and generalization of fear, which was now investigated. We now report that A2AR blockade through systemic administration of the A2AR antagonist SCH58261 immediately after contextual fear conditioning (within the consolidation window), accelerated fear generalization. Conversely, A2AR activation with CGS21680 decreased fear generalization. Ex vivo electrophysiological recordings of field excitatory post-synaptic potentials (fEPSPs) in CA3-CA1 synapses and of population spikes in the lateral amygdala (LA), showed that the effect of SCH58261 is associated with a reversion of fear conditioning-induced decrease of long-term potentiation (LTP) in the dorsal hippocampus (DH) and with increased amplitude of LA LTP in conditioned animals. These data suggest that A2AR are engaged during contextual fear consolidation, controlling long-term potentiation mechanisms in both DH and LA during fear consolidation, impacting on fear generalization; this supports targeting A2AR during fear consolidation to control aberrant fear processing in PTSD and other fear-related disorders.
Assuntos
Potenciação de Longa Duração , Sinapses , Ratos , Animais , Sinapses/metabolismo , Memória/fisiologia , Adenosina/farmacologia , Medo/fisiologia , Hipocampo/metabolismo , Receptor A2A de Adenosina/metabolismoRESUMO
The intracerebroventricular (icv) injection of amyloid peptides (Aß) models Alzheimer's disease (AD) in mice, as typified by the onset within 15 days of deficits of memory and of hippocampal long-term potentiation (LTP) that are prevented by the blockade of adenosine A2A receptors (A2AR). Since A2AR overfunction is sufficient to trigger memory deficits, we tested if A2AR were upregulated in hippocampal synapses before the onset of memory deficits to support the hypothesis that A2AR overfunction could be a trigger of AD. Six to eight days after Aß-icv injection, mice displayed no alterations of hippocampal dependent memory; however, they presented an increased excitability of hippocampal synapses, a slight increase in LTP magnitude in Schaffer fiber-CA1 pyramid synapses and an increased density of A2AR in hippocampal synapses. A2AR blockade with SCH58261 (50 nM) normalized excitability and LTP in hippocampal slices from mice sacrificed 7-8 days after Aß-icv injection. Fifteen days after Aß-icv injection, mice displayed evident deficits of hippocampal-dependent memory deterioration, with reduced hippocampal CA1 LTP but no hyperexcitability and a sustained increase in synaptic A2AR, which blockade restored LTP magnitude. This shows that the upregulation of synaptic A2AR precedes the onset of deterioration of memory and of hippocampal synaptic plasticity, supporting the hypothesis that the overfunction of synaptic A2AR could be a trigger of memory deterioration in AD.
Assuntos
Doença de Alzheimer , Animais , Camundongos , Regulação para Cima , Doença de Alzheimer/induzido quimicamente , Receptor A2A de Adenosina , Plasticidade Neuronal , Adenosina , Transtornos da Memória/induzido quimicamenteRESUMO
Caffeic acid is a polyphenolic compound present in a vast array of dietary components. We previously showed that caffeic acid reduces the burden of brain ischemia joining evidence by others that it can attenuate different brain diseases. However, it is unknown if caffeic acid affects information processing in neuronal networks. Thus, we now used electrophysiological recordings in mouse hippocampal slices to test if caffeic acid directly affected synaptic transmission, plasticity and dysfunction caused by oxygen-glucose deprivation (OGD), an in vitro ischemia model. Caffeic acid (1-10 µM) was devoid of effect on synaptic transmission and paired-pulse facilitation in Schaffer collaterals-CA1 pyramidal synapses. Also, the magnitude of either hippocampal long-term potentiation (LTP) or the subsequent depotentiation were not significantly modified by 10 µM caffeic acid. However, caffeic acid (10 µM) increased the recovery of synaptic transmission upon re-oxygenation following 7 min of OGD. Furthermore, caffeic acid (10 µM) also recovered plasticity after OGD, as heralded by the increased magnitude of LTP after exposure. These findings show that caffeic acid does not directly affect synaptic transmission and plasticity but can indirectly affect other cellular targets to correct synaptic dysfunction. Unraveling the molecular mechanisms of action of caffeic acid may allow the design of hitherto unrecognized novel neuroprotective strategies.
Assuntos
Hipocampo , Transmissão Sináptica , Camundongos , Animais , Transmissão Sináptica/fisiologia , Potenciação de Longa Duração/fisiologia , Isquemia , Plasticidade Neuronal/fisiologiaRESUMO
Increased ATP release and its extracellular catabolism through CD73 (ecto-5'-nucleotidase) lead to the overactivation of adenosine A2A receptors (A2AR), which occurs in different brain disorders. A2AR blockade blunts mood and memory dysfunction caused by repeated stress, but it is unknown if increased ATP release coupled to CD73-mediated formation of extracellular adenosine is responsible for A2AR overactivation upon repeated stress. This was now investigated in adult rats subject to repeated stress for 14 consecutive days. Frontocortical and hippocampal synaptosomes from stressed rats displayed an increased release of ATP upon depolarization, coupled to an increased density of vesicular nucleotide transporters and of CD73. The continuous intracerebroventricular delivery of the CD73 inhibitor α,ß-methylene ADP (AOPCP, 100 µM) during restraint stress attenuated mood and memory dysfunction. Slice electrophysiological recordings showed that restraint stress decreased long-term potentiation both in prefrontocortical layer II/III-layer V synapses and in hippocampal Schaffer fibers-CA1 pyramid synapses, which was prevented by AOPCP, an effect occluded by adenosine deaminase and by the A2AR antagonist SCH58261. These results indicate that increased synaptic ATP release coupled to CD73-mediated formation of extracellular adenosine contributes to mood and memory dysfunction triggered by repeated restraint stress. This prompts considering interventions decreasing ATP release and CD73 activity as novel strategies to mitigate the burden of repeated stress.
Assuntos
5'-Nucleotidase , Adenosina , Animais , Ratos , 5'-Nucleotidase/metabolismo , Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Receptor A2A de Adenosina/metabolismo , Sinapses/metabolismo , Sinaptossomos/metabolismo , Estresse Fisiológico , Fenômenos EletrofisiológicosRESUMO
Adenosine receptors mainly control synaptic function, and excessive activation of adenosine receptors may worsen the onset of many neurological disorders. Accordingly, the regular intake of moderate doses of caffeine antagonizes adenosine receptors and affords robust neuroprotection. Although caffeine intake alters brain functional connectivity and multi-omics analyses indicate that caffeine intake modifies synaptic and metabolic processes, it is unclear how caffeine intake affects behavior, synaptic plasticity and its modulation by adenosine. We now report that male mice drinking caffeinated water (0.3 g/L) for 2 weeks were behaviorally indistinguishable (locomotion, mood, memory) from control mice (drinking water) and displayed superimposable synaptic plasticity (long-term potentiation) in different brain areas (hippocampus, prefrontal cortex, amygdala). Moreover, there was a general preservation of the efficiency of adenosine A1 and A2A receptors to control synaptic transmission and plasticity, although there was a tendency for lower levels of endogenous adenosine ensuring A1 receptor-mediated inhibition. In spite of similar behavioral and neurophysiological function, caffeine intake increased the energy charge and redox state of cortical synaptosomes. This increased metabolic competence likely involved a putative increase in the glycolytic rate in synapses and a prospective greater astrocyte-synapse lactate shuttling. It was concluded that caffeine intake does not trigger evident alterations of behavior or of synaptic plasticity but increases the metabolic competence of synapses, which might be related with the previously described better ability of animals consuming caffeine to cope with deleterious stimuli triggering brain dysfunction.
Assuntos
Adenosina , Cafeína , Masculino , Camundongos , Animais , Cafeína/farmacologia , Adenosina/farmacologia , Adenosina/metabolismo , Estudos Prospectivos , Receptores Purinérgicos P1/metabolismo , Hipocampo/metabolismoRESUMO
Extracellular ATP can be a danger signal, but its role in striatal circuits afflicted in Parkinson's disease (PD) is unclear and was now investigated. ATP was particularly released at high stimulation intensities from purified striatal nerve terminals of mice, which were endowed with different ATP-P2 receptors (P2R), although P2R antagonists did not alter corticostriatal transmission or plasticity. Instead, ATP was extracellularly catabolized into adenosine through CD73 to activate adenosine A2A receptors (A2AR) modulating corticostriatal long-term potentiation (LTP) in mice. In the presymptomatic phase of a 6-hydroxydopamine rat model of PD, ATP release from striatal nerve terminals was increased and was responsible for a greater impact of CD73 and A2AR on corticostriatal LTP. These observations identify increased ATP release and ATP-derived formation of extracellular adenosine bolstering A2AR activation as a key pathway responsible for abnormal synaptic plasticity in circuits involved in the onset of PD motor symptoms. The translation of these findings to humans prompts extending the use of A2AR antagonists from only co-adjuvants of motor control in Parkinsonian patients to neuroprotective drugs delaying the onset of motor symptoms.
Assuntos
Adenosina , Doença de Parkinson , Ratos , Humanos , Camundongos , Animais , Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Potenciação de Longa Duração , Plasticidade NeuronalRESUMO
Extracellular ATP is a danger signal to the brain and contributes to neurodegeneration in animal models of Alzheimer's disease through its extracellular catabolism by CD73 to generate adenosine, bolstering the activation of adenosine A2A receptors (A2AR). Convulsive activity leads to increased ATP release, with the resulting morphological alterations being eliminated by A2AR blockade. However, it is not known if upon convulsions there is a CD73-mediated coupling between ATP release and A2AR overactivation, causing neurodegeneration. We now show that kainate-induced convulsions trigger a parallel increase of ATP release and of CD73 and A2AR densities in synapses and astrocytes of the mouse hippocampus. Notably, the genetic deletion of CD73 attenuates neuronal degeneration but has no impact on astrocytic modifications in the hippocampus upon kainate-induced convulsions. Furthermore, kainate-induced convulsions cause a parallel deterioration of hippocampal long-term potentiation (LTP) and hippocampal-dependent memory performance, which is eliminated by knocking out CD73. This demonstrates the key role of the ATP release/CD73/A2AR pathway to selectively control synaptic dysfunction and neurodegeneration following an acute brain insult, paving the way to consider CD73 as a new therapeutic target to prevent neuronal damage upon acute brain damage.
Assuntos
5'-Nucleotidase/metabolismo , Trifosfato de Adenosina/metabolismo , Astrócitos/metabolismo , Hipocampo/metabolismo , Neurônios/metabolismo , Receptor A2A de Adenosina/metabolismo , Convulsões/metabolismo , Sinapses/metabolismo , 5'-Nucleotidase/genética , Animais , Astrócitos/efeitos dos fármacos , Agonistas de Aminoácidos Excitatórios/toxicidade , Hipocampo/efeitos dos fármacos , Ácido Caínico/toxicidade , Potenciação de Longa Duração/efeitos dos fármacos , Potenciação de Longa Duração/fisiologia , Memória/efeitos dos fármacos , Memória/fisiologia , Camundongos , Camundongos Knockout , Doenças Neurodegenerativas/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Convulsões/induzido quimicamente , Sinapses/efeitos dos fármacosRESUMO
The increased healthspan afforded by coffee intake provides novel opportunities to identify new therapeutic strategies. Caffeine has been proposed to afford benefits through adenosine A2A receptors, which can control synaptic dysfunction underlying some brain disease. However, decaffeinated coffee and other main components of coffee such as chlorogenic acids, also attenuate brain dysfunction, although it is unknown if they control synaptic function. We now used electrophysiological recordings in mouse hippocampal slices to test if realistic concentrations of chlorogenic acids directly affect synaptic transmission and plasticity. 3-(3,4-dihydroxycinnamoyl)quinic acid (CA, 1-10 µM) and 5-O-(trans-3,4-dihydroxycinnamoyl)-D-quinic acid (NCA, 1-10 µM) were devoid of effect on synaptic transmission, paired-pulse facilitation or long-term potentiation (LTP) and long-term depression (LTD) in Schaffer collaterals-CA1 pyramidal synapses. However, CA and NCA increased the recovery of synaptic transmission upon re-oxygenation following 7 min of oxygen/glucose deprivation, an in vitro ischemia model. Also, CA and NCA attenuated the shift of LTD into LTP observed in hippocampal slices from animals with hippocampal-dependent memory deterioration after exposure to ß-amyloid 1-42 (2 nmol, icv), in the context of Alzheimer's disease. These findings show that chlorogenic acids do not directly affect synaptic transmission and plasticity but can indirectly affect other cellular targets to correct synaptic dysfunction. Unraveling the molecular mechanisms of action of chlorogenic acids will allow the design of hitherto unrecognized novel neuroprotective strategies.
Assuntos
Ácido Clorogênico/farmacologia , Hipocampo/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Neurotransmissores/farmacologia , Transmissão Sináptica/efeitos dos fármacos , Doença de Alzheimer/patologia , Animais , Modelos Animais de Doenças , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Angelman syndrome (AS) is a neurogenetic disorder involving ataxia and motor dysfunction, resulting from the absence of the maternally inherited functional Ube3a protein in neurons. Since adenosine A2A receptor (A2AR) blockade relieves synaptic and motor impairments in Parkinson's or Machado-Joseph's diseases, we now tested if A2AR blockade was also effective in attenuating motor deficits in an AS (Ube3am-/p+) mouse model and if this involved correction of synaptic alterations in striatum and cerebellum. Chronic administration of the A2AR antagonist SCH58261 (0.1 mg/kg/day, ip) promoted motor learning of AS mice in the accelerating-rotarod task and rescued the grip strength impairment of AS animals. These motor impairments were accompanied by synaptic alterations in cerebellum and striatum typified by upregulation of synaptophysin and vesicular GABA transporters (vGAT) in the cerebellum of AS mice along with a downregulation of vGAT, vesicular glutamate transporter 1 (vGLUT1) and the dopamine active transporter in AS striatum. Notably, A2AR blockade prevented the synaptic alterations found in AS mice cerebellum as well as the downregulation of striatal vGAT and vGLUT1. This provides the first indications that A2AR blockade may counteract the characteristic motor impairments and synaptic changes of AS, although more studies are needed to unravel the underlying mechanisms.
Assuntos
Antagonistas do Receptor A2 de Adenosina/farmacologia , Síndrome de Angelman/patologia , Síndrome de Angelman/fisiopatologia , Cerebelo/fisiopatologia , Corpo Estriado/fisiopatologia , Atividade Motora , Receptor A2A de Adenosina/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Animais , Biomarcadores/metabolismo , Modelos Animais de Doenças , Fosfoproteína 32 Regulada por cAMP e Dopamina/metabolismo , Força da Mão , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurotransmissores/metabolismo , Fosforilação/efeitos dos fármacos , Pirimidinas/farmacologia , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Triazóis/farmacologia , Regulação para Cima/efeitos dos fármacosRESUMO
Angelman syndrome (AS) is a neurodevelopmental disorder caused by loss of function of the maternally inherited Ube3a neuronal protein, whose main features comprise severe intellectual disabilities and motor impairments. Previous studies with the Ube3am-/p+ mouse model of AS revealed deficits in synaptic plasticity and memory. Since adenosine A2A receptors (A2AR) are powerful modulators of aberrant synaptic plasticity and A2AR blockade prevents memory dysfunction in various brain diseases, we tested if A2AR could control deficits of memory and hippocampal synaptic plasticity in AS. We observed that Ube3am-/p+ mice were unable to resort to hippocampal-dependent search strategies when tested for learning and memory in the Morris water maze; this was associated with a decreased magnitude of long-term depression (LTD) in CA1 hippocampal circuits. There was an increased density of A2AR in the hippocampus of Ube3am-/p+ mice and their chronic treatment with the selective A2AR antagonist SCH58261 (0.1â¯mg/kg/day, ip) restored both hippocampal-dependent learning strategies, as well as LTD deficits. Altogether, this study provides the first evidence of a role of A2AR as a new prospective therapeutic target to manage learning deficits in AS.
Assuntos
Adenosina/metabolismo , Síndrome de Angelman/metabolismo , Hipocampo/fisiopatologia , Plasticidade Neuronal/fisiologia , Animais , Modelos Animais de Doenças , Hipocampo/metabolismo , Aprendizagem/fisiologia , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Adenosine A2A receptors (A2AR) overfunction causes synaptic and memory dysfunction in early Alzheimer's disease (AD). In a ß-amyloid (Aß1-42)-based model of early AD, we now unraveled that this involves an increased synaptic release of ATP coupled to an increased density and activity of ecto-5'-nucleotidase (CD73)-mediated formation of adenosine selectively activating A2AR. Thus, CD73 inhibition with α,ß-methylene-ADP impaired long-term potentiation (LTP) in mouse hippocampal slices, which is occluded upon previous superfusion with the A2AR antagonist SCH58261. Furthermore, α,ß-methylene-ADP did not alter LTP amplitude in global A2AR knockout (KO) and in forebrain neuron-selective A2AR-KO mice, but inhibited LTP amplitude in astrocyte-selective A2AR-KO mice; this shows that CD73-derived adenosine solely acts on neuronal A2AR. In agreement with the concept that ATP is a danger signal in the brain, ATP release from nerve terminals is increased after intracerebroventricular Aß1-42 administration, together with CD73 and A2AR upregulation in hippocampal synapses. Importantly, this increased CD73 activity is critically required for Aß1-42 to impair synaptic plasticity and memory since Aß1-42-induced synaptic and memory deficits were eliminated in CD73-KO mice. These observations establish a key regulatory role of CD73 activity over neuronal A2AR and imply CD73 as a novel target for modulation of early AD.
Assuntos
5'-Nucleotidase/metabolismo , Adenosina/metabolismo , Doença de Alzheimer/metabolismo , Potenciação de Longa Duração/fisiologia , Receptor A2A de Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Modelos Animais de Doenças , Hipocampo/metabolismo , Masculino , Aprendizagem em Labirinto/fisiologia , Transtornos da Memória/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos KnockoutRESUMO
The hippocampus is a brain region involved in processing both memory and emotions, through a preferential involvement of the dorsal hippocampus (DH) and ventral hippocampus (VH), respectively. Adenosine A1 and A2A receptors (A1 R and A2A R) control both mood and memory, but it is not known if there is a different adenosine modulation of synaptic plasticity along the hippocampal axis. Using adult, C57BL/6 male mice, we show that both A1 R and A2A R were more abundant in DH compared with VH. However, recordings of field excitatory postsynaptic potentials at Schaffer collaterals-CA1 pyramidal synapses revealed that A1 R were equi-effective to inhibit basal excitatory synaptic transmission in DH and VH, but endogenous A1 R activation was more effective to depress the probability of release in VH. In contrast, the selective A2A R antagonist (SCH58261, 50 nM) controlled both long-term potentiation (induced by a high frequency stimulation protocol) and long-term depression (induced by a low frequency stimulation protocol) selectively in DH rather than VH, whereas the selective A1 R antagonist (DPCPX, 100 nM) revealed a similar tonic inhibition of long-term depression in DH and VH. These findings show a different control of synaptic plasticity by the adenosine modulation system in the dorsal and ventral poles of the hippocampus, which may underlie a different efficiency of the adenosine system to control mood and memory.
Assuntos
Hipocampo/metabolismo , Plasticidade Neuronal/fisiologia , Receptor A1 de Adenosina/metabolismo , Receptor A2A de Adenosina/metabolismo , Antagonistas do Receptor A1 de Adenosina/farmacologia , Antagonistas do Receptor A2 de Adenosina/farmacologia , Animais , Hipocampo/química , Hipocampo/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/efeitos dos fármacos , Técnicas de Cultura de Órgãos , Receptor A1 de Adenosina/análise , Receptor A2A de Adenosina/análiseRESUMO
S17 is a clonogenic bone marrow stromal (BMS) cell line derived from mouse that has been extensively used to assess both human and murine hematopoiesis support capacity. However, very little is known about the expression of potassium ion channels and their function in cell survival and migration in these cells. Thus, the present study was designed to characterize potassium ion channels using electrophysiological and molecular biological approaches in S17 BMS cells. The whole-cell configuration of the patch clamp technique has been applied to identify potassium ion currents and reverse transcription polymerase chain reaction (RT-PCR) used to determine their molecular identities. Based on gating kinetics and pharmacological modulation of the macroscopic currents we found the presence of four functional potassium ion channels in S17 BMS cells. These include a current rapidly activated and inactivated, tetraethylammonium-sensitive, (IKV ) in most (50%) cells; a fast activated and rapidly inactivating A-type K + current (IK A -like); a delayed rectifier K + current (IK DR ) and an inward rectifier potassium current (IK IR ), found in, respectively 4.5%, 26% and 24% of these cells. RT-PCR confirmed the presence of mRNA transcripts for the alpha subunit of the corresponding functional ion channels. Additionally, functional assays were performed to investigate the importance of potassium currents in cell survival and migration. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analyses revealed a reduction in cell viability, while wound healing assays revealed reduced migration potential in cells incubated with different potassium channel blockers. In conclusion, our data suggested that potassium currents might play a role in the maintenance of overall S17 cell ionic homeostasis directly affecting cell survival and migration.
Assuntos
Movimento Celular , Células-Tronco Mesenquimais/metabolismo , Canais de Potássio/metabolismo , Potássio/metabolismo , Animais , Linhagem Celular , Movimento Celular/efeitos dos fármacos , Sobrevivência Celular , Ativação do Canal Iônico , Cinética , Potenciais da Membrana , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio/efeitos dos fármacos , Canais de Potássio/genética , Transdução de SinaisRESUMO
Alzheimer's disease (AD) begins with a deficit of synaptic function and adenosine A2A receptors (A2AR) are mostly located in synapses controlling synaptic plasticity. The over-activation of adenosine A2A receptors (A2AR) causes memory deficits and the blockade of A2AR prevents memory damage in AD models. We now enquired if this prophylactic role of A2AR might be extended to a therapeutic potential. We used the triple transgenic model of AD (3xTg-AD) and defined that the onset of memory dysfunction occurred at 4â¯months of age in the absence of locomotor or emotional alterations. At the onset of memory deficits, 3xTg mice displayed a decreased density of markers of excitatory synapses (10.6⯱â¯3.8% decrease of vGluT1) without neuronal or glial overt damage and an increase of synaptic A2AR in the hippocampus (130⯱â¯22%). After the onset of memory deficits in 3xTg-AD mice, a three weeks treatment with the selective A2AR antagonist normalized the up-regulation of hippocampal A2AR and restored hippocampal-dependent reference memory, as well as the decrease of hippocampal synaptic plasticity (60.0⯱â¯3.7% decrease of long-term potentiation amplitude) and the decrease of global (syntaxin-I) and glutamatergic synaptic markers (vGluT1). These findings show a therapeutic-like ability of A2AR antagonists to recover synaptic and memory dysfunction in early AD.
Assuntos
Antagonistas do Receptor A2 de Adenosina/uso terapêutico , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Transtornos da Memória/genética , Transtornos da Memória/metabolismo , Plasticidade Neuronal/fisiologia , Antagonistas do Receptor A2 de Adenosina/farmacologia , Doença de Alzheimer/tratamento farmacológico , Animais , Modelos Animais de Doenças , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Transtornos da Memória/tratamento farmacológico , Camundongos , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Plasticidade Neuronal/efeitos dos fármacos , Projetos Piloto , Receptor A2A de Adenosina/metabolismoRESUMO
Adenosine A2A receptors (A2ARs) were recently described to control synaptic plasticity and network activity in the prefrontal cortex (PFC). We now probed the role of these PFC A2AR by evaluating the behavioral performance (locomotor activity, anxiety-related behavior, cost-benefit decision making and working memory) of rats upon downregulation of A2AR selectively in the prelimbic medial PFC (PLmPFC) via viral small hairpin RNA targeting the A2AR (shA2AR). The most evident alteration observed in shA2AR-treated rats, when compared to sh-control (shCTRL)-treated rats, was a decrease in the choice of the large reward upon an imposed delay of 15 s assessed in a T-maze-based cost-benefit decision-making paradigm, suggestive of impulsive decision making. Spontaneous locomotion in the open field was not altered, suggesting no changes in exploratory behavior. Furthermore, rats treated with shA2AR in the PLmPFC also displayed a tendency for higher anxiety levels in the elevated plus maze (less entries in the open arms), but not in the open field test (time spent in the center was not affected). Finally, working memory performance was not significantly altered, as revealed by the spontaneous alternation in the Y-maze test and the latency to reach the platform in the repeated trial Morris water maze. These findings constitute the first direct demonstration of a role of PFC A2AR in the control of behavior in physiological conditions, showing their major contribution for the control of delay-based cost-benefit decisions.
RESUMO
Neurodegeneration is a process transversal to neuropsychiatric diseases and the understanding of its mechanisms should allow devising strategies to prevent this irreversible step in brain diseases. Neurodegeneration caused by seizures is a critical step in the aggravation of temporal lobe epilepsy, but its mechanisms remain undetermined. Convulsions trigger an elevation of extracellular adenosine and upregulate adenosine A2A receptors (A2AR), which have been associated with the control of neurodegenerative diseases. Using the rat and mouse kainate model of temporal lobe epilepsy, we now tested whether A2AR control convulsions-induced hippocampal neurodegeneration. The pharmacological or genetic blockade of A2AR did not affect kainate-induced convulsions but dampened the subsequent neurotoxicity. This neurotoxicity began with a rapid A2AR upregulation within glutamatergic synapses (within 2 h), through local translation of synaptic A2AR mRNA. This bolstered A2AR-mediated facilitation of glutamate release and of long-term potentiation (LTP) in CA1 synapses (4 h), triggered a subsequent synaptotoxicity, heralded by decreased synaptic plasticity and loss of synaptic markers coupled to calpain activation (12 h), that predated overt neuronal loss (24 h). All modifications were prevented by the deletion of A2AR selectively in forebrain neurons. This shows that synaptic A2AR critically control synaptic excitotoxicity, which underlies the development of convulsions-induced neurodegeneration.
Assuntos
Convulsivantes/toxicidade , Ácido Caínico/toxicidade , Degeneração Neural/etiologia , Degeneração Neural/metabolismo , Neurônios/metabolismo , Receptor A2A de Adenosina/metabolismo , Antagonistas do Receptor A2 de Adenosina/uso terapêutico , Tonsila do Cerebelo/fisiologia , Animais , Células Cultivadas , Epilepsia/complicações , Epilepsia/tratamento farmacológico , Epilepsia/etiologia , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Excitação Neurológica/efeitos dos fármacos , Excitação Neurológica/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Degeneração Neural/prevenção & controle , Neurônios/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Pirimidinas/uso terapêutico , Ratos , Ratos Wistar , Receptor A2A de Adenosina/genética , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genética , Triazóis/uso terapêuticoRESUMO
Diabetes affects the morphology and plasticity of the hippocampus, and leads to learning and memory deficits. Caffeine has been proposed to prevent memory impairment upon multiple chronic disorders with neurological involvement. We tested whether long-term caffeine consumption prevents type 2 diabetes (T2D)-induced spatial memory impairment and hippocampal alterations, including synaptic degeneration, astrogliosis, and metabolic modifications. Control Wistar rats and Goto-Kakizaki (GK) rats that develop T2D were treated with caffeine (1 g/L in drinking water) for 4 months. Spatial memory was evaluated in a Y-maze. Hippocampal metabolic profile and glucose homeostasis were investigated by 1H magnetic resonance spectroscopy. The density of neuronal, synaptic, and glial-specific markers was evaluated by Western blot analysis. GK rats displayed reduced Y-maze spontaneous alternation and a lower amplitude of hippocampal long-term potentiation when compared to controls, suggesting impaired hippocampal-dependent spatial memory. Diabetes did not impact the relation of hippocampal to plasma glucose concentrations, but altered the neurochemical profile of the hippocampus, such as increased in levels of the osmolites taurine (P < 0.001) and myo-inositol (P < 0.05). The diabetic hippocampus showed decreased density of the presynaptic proteins synaptophysin (P < 0.05) and SNAP25 (P < 0.05), suggesting synaptic degeneration, and increased GFAP (P < 0.001) and vimentin (P < 0.05) immunoreactivities that are indicative of astrogliosis. The effects of caffeine intake on hippocampal metabolism added to those of T2D, namely reducing myo-inositol levels (P < 0.001) and further increasing taurine levels (P < 0.05). Caffeine prevented T2D-induced alterations of GFAP, vimentin and SNAP25, and improved memory deficits. We conclude that caffeine consumption has beneficial effects counteracting alterations in the hippocampus of GK rats, leading to the improvement of T2D-associated memory impairment.
RESUMO
Caffeine prophylactically prevents mood and memory impairments through adenosine A2A receptor (A2AR) antagonism. A2AR antagonists also therapeutically revert mood and memory impairments, but it is not known if caffeine is also therapeutically or only prophylactically effective. Since depression is accompanied by mood and memory alterations, we now explored if chronic (4 weeks) caffeine consumption (0.3 g/L) reverts mood and memory impairment in helpless mice (HM, 12 weeks old), a bred-based model of depression. HM displayed higher immobility in the tail suspension and forced swimming tests, greater anxiety in the elevated plus maze, and poorer memory performance (modified Y-maze and object recognition). HM also had reduced density of synaptic (synaptophysin, SNAP-25), namely, glutamatergic (vGluT1; -22 ± 7 %) and GABAergic (vGAT; -23 ± 8 %) markers in the hippocampus. HM displayed higher A2AR density (72 ± 6 %) in hippocampal synapses, an enhanced facilitation of hippocampal glutamate release by the A2AR agonist, CGS21680 (30 nM), and a larger LTP amplitude (54 ± 8 % vs. 21 ± 5 % in controls) that was restored to control levels (30 ± 10 %) by the A2AR antagonist, SCH58261 (50 nM). Notably, caffeine intake reverted memory deficits and reverted the loss of hippocampal synaptic markers but did not affect helpless or anxiety behavior. These results reinforce the validity of HM as an animal model of depression by showing that they also display reference memory deficits. Furthermore, caffeine intake selectively reverted memory but not mood deficits displayed by HM, which are associated with an increased density and functional impact of hippocampal A2AR controlling synaptic glutamatergic function.
Assuntos
Cafeína/uso terapêutico , Depressão/metabolismo , Ácido Glutâmico/metabolismo , Transtornos da Memória/metabolismo , Transtornos do Humor/metabolismo , Receptor A2A de Adenosina/biossíntese , Animais , Cafeína/farmacologia , Estimulantes do Sistema Nervoso Central/farmacologia , Estimulantes do Sistema Nervoso Central/uso terapêutico , Depressão/tratamento farmacológico , Depressão/psicologia , Relação Dose-Resposta a Droga , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Transtornos da Memória/tratamento farmacológico , Transtornos da Memória/psicologia , Camundongos , Transtornos do Humor/tratamento farmacológico , Transtornos do Humor/psicologia , Especificidade da Espécie , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologiaRESUMO
The consumption of caffeine (an adenosine receptor antagonist) correlates inversely with depression and memory deterioration, and adenosine A2A receptor (A2AR) antagonists emerge as candidate therapeutic targets because they control aberrant synaptic plasticity and afford neuroprotection. Therefore we tested the ability of A2AR to control the behavioral, electrophysiological, and neurochemical modifications caused by chronic unpredictable stress (CUS), which alters hippocampal circuits, dampens mood and memory performance, and enhances susceptibility to depression. CUS for 3 wk in adult mice induced anxiogenic and helpless-like behavior and decreased memory performance. These behavioral changes were accompanied by synaptic alterations, typified by a decrease in synaptic plasticity and a reduced density of synaptic proteins (synaptosomal-associated protein 25, syntaxin, and vesicular glutamate transporter type 1), together with an increased density of A2AR in glutamatergic terminals in the hippocampus. Except for anxiety, for which results were mixed, CUS-induced behavioral and synaptic alterations were prevented by (i) caffeine (1 g/L in the drinking water, starting 3 wk before and continued throughout CUS); (ii) the selective A2AR antagonist KW6002 (3 mg/kg, p.o.); (iii) global A2AR deletion; and (iv) selective A2AR deletion in forebrain neurons. Notably, A2AR blockade was not only prophylactic but also therapeutically efficacious, because a 3-wk treatment with the A2AR antagonist SCH58261 (0.1 mg/kg, i.p.) reversed the mood and synaptic dysfunction caused by CUS. These results herald a key role for synaptic A2AR in the control of chronic stress-induced modifications and suggest A2AR as candidate targets to alleviate the consequences of chronic stress on brain function.
Assuntos
Cafeína/farmacologia , Transtornos da Memória/prevenção & controle , Transtornos do Humor/prevenção & controle , Neurônios/efeitos dos fármacos , Receptor A2A de Adenosina/efeitos dos fármacos , Estresse Psicológico/complicações , Animais , Masculino , Transtornos da Memória/etiologia , Camundongos , Camundongos Endogâmicos C57BL , Transtornos do Humor/etiologia , Neurônios/metabolismoRESUMO
Cognitive impairments in Huntington's disease (HD) are attributed to a dysfunction of the cortico-striatal pathway and significantly affect the quality of life of the patients, but this has not been a therapeutic focus in HD to date. We postulated that adenosine A(2A) receptors (A(2A)R), located at pre- and post-synaptic elements of the cortico-striatal pathways, modulate striatal neurotransmission and synaptic plasticity and cognitive behaviors. To critically evaluate the ability of A(2A)R inactivation to prevent cognitive deficits in early HD, we cross-bred A(2A)R knockout (KO) mice with two R6/2 transgenic lines of HD (CAG120 and CAG240) to generate two double transgenic R6/2-CAG120-A(2A)R KO and R6/2-CAG240-A(2A)R KO mice and their corresponding wild-type (WT) littermates. Genetic inactivation of A(2A)R prevented working memory deficits induced by R6/2-CAG120 at post-natal week 6 and by R6/2-CAG240 at post-natal month 2 and post-natal month 3, without modifying motor deficits. Similarly the A2(A)R antagonist KW6002 selectively reverted working memory deficits in R6/2-CAG240 mice at post-natal month 3. The search for possible mechanisms indicated that the genetic inactivation of A(2A)R did not affect ubiquitin-positive neuronal inclusions, astrogliosis or Thr-75 phosphorylation of DARPP-32 in the striatum. Importantly, A(2A)R blockade preferentially controlled long-term depression at cortico-striatal synapses in R6/2-CAG240 at post-natal week 6. The reported reversal of working memory deficits in R6/2 mice by the genetic and pharmacological inactivation of A(2A)R provides a proof-of-principle for A(2A)R as novel targets to reverse cognitive deficits in HD, likely by controlling LTD deregulation.