RESUMO
Excessive inhibition of the external globus pallidus (GPe) by striatal GABAergic neurons is considered a central mechanism contributing to motor symptoms of Parkinson's disease (PD). While electrophysiological findings support this view, behavioral studies assessing the beneficial effects of global GPe activations are scarce and the reported results are controversial. We used an optogenetic approach and the standard unilateral 6-hydroxydopamine nigrostriatal dopamine (DA) lesion model of PD to explore the effects of GPe photostimulation on motor deficits in mice. Global optogenetic GPe inhibition was used in normal mice to verify whether it reproduced the typical motor impairment induced by DA lesions. GPe activation improved ipsilateral circling, contralateral forelimb akinesia, locomotor hypoactivity, and bradykinesia in 6-OHDA-lesioned mice at ineffective photostimulation parameters (532 nm, 5 Hz, 3 mW) in normal mice. GPe photoinhibition (450 nm, 12 mW) had no effect on locomotor activity and forelimb use in normal mice. Bilateral photoinhibition (450 nm, 6 mW/side) reduced directed exploration and improved working memory performances indicating that recruitment of GPe in physiological conditions may depend on the behavioral task involved. Collectively, these findings shed new light on the functional role of GPe and suggest that it is a promising target for neuromodulatory restoration of motor deficits in PD.
Assuntos
Doença de Parkinson , Camundongos , Animais , Doença de Parkinson/etiologia , Doença de Parkinson/terapia , Doença de Parkinson/patologia , Globo Pálido/patologia , Oxidopamina , Optogenética , Corpo Estriado , Dopamina/fisiologia , Hipocinesia/induzido quimicamente , Hipocinesia/terapia , Hipocinesia/patologiaRESUMO
Alterations of zinc homeostasis have long been implicated in Parkinson's disease (PD). Zinc plays a complex role as both deficiency and excess of intracellular zinc levels have been incriminated in the pathophysiology of the disease. Besides its role in multiple cellular functions, Zn2+ also acts as a synaptic transmitter in the brain. In the forebrain, subset of glutamatergic neurons, namely cortical neurons projecting to the striatum, use Zn2+ as a messenger alongside glutamate. Overactivation of the cortico-striatal glutamatergic system is a key feature contributing to the development of PD symptoms and dopaminergic neurotoxicity. Here, we will cover recent evidence implicating synaptic Zn2+ in the pathophysiology of PD and discuss its potential mechanisms of actions. Emphasis will be placed on the functional interaction between Zn2+ and glutamatergic NMDA receptors, the most extensively studied synaptic target of Zn2+.
Assuntos
Doença de Parkinson/fisiopatologia , Sinapses/fisiologia , Zinco/fisiologia , Animais , Gânglios da Base/fisiopatologia , Proteínas de Transporte de Cátions/deficiência , Córtex Cerebral/fisiopatologia , Quelantes/farmacologia , Quelantes/uso terapêutico , Corpo Estriado/fisiopatologia , Feminino , Homeostase , Humanos , Líquido Intracelular/metabolismo , Masculino , Camundongos , Camundongos Knockout , Degeneração Neural/fisiopatologia , Oxidopamina/toxicidade , Transtornos Parkinsonianos/induzido quimicamente , Transtornos Parkinsonianos/fisiopatologia , Ratos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/fisiologia , Transmissão Sináptica/fisiologiaRESUMO
Hyperactivity of glutamatergic corticostrial pathways is recognized as a key pathophysiological mechanism contributing to development of PD symptoms and dopaminergic neurotoxicity. Subset of corticostriatal projection neurons uses Zn2+ as a co-transmitter alongside glutamate, but the role of synaptically released Zn2+ in PD remains unexplored. We used genetically modified mice and pharmacological tools in combination with 6-hydroxydopamine (6-OHDA) lesion models of PD to investigate the contribution of synaptic zinc to disease associated behavioral deficits and neurodegeneration. Vesicular zinc transporter-3 (ZnT3) knockout mice lacking releasable Zn2+ were more resistant to locomotor deficit and memory impairment of nigrostriatal dopamine (DA) denervation compared to wildtype littermates. The loss of striatal dopaminergic fibers was comparable between genotypes, indicating that synaptically released Zn2+ contributes to behavioral deficits but not neurotoxic effects of 6-OHDA. To gain further insight into the mechanisms of Zn2+ actions, we used the extracellular Zn2+ chelator CaEDTA and knock-in mice lacking the high affinity Zn2+ inhibition of GluN2A-containing NMDA receptors (GluN2A-NMDARs). Acute chelation of extracellular Zn2+ in the striatum restored locomotor deficit of 6-OHDA lesion, confirming that synaptic Zn2+ suppresses locomotor behavior. Disruption of the Zn2+-GluN2A interaction had, on the other hand, no impact on locomotor deficit or neurotoxic effect of 6-OHDA. Collectively, these findings provide clear evidence for the implication of striatal synaptic Zn2+ in the pathophysiology of PD. They unveil that synaptic Zn2+ plays predominantly a detrimental role by promoting motor and cognitive deficits caused by nigrostriatal DA denervation, pointing towards new therapeutic interventions.
Assuntos
Cognição , Locomoção , Doença de Parkinson/metabolismo , Doença de Parkinson/psicologia , Zinco/metabolismo , Animais , Comportamento Animal , Proteínas de Transporte de Cátions/genética , Corpo Estriado/metabolismo , Modelos Animais de Doenças , Masculino , Memória/fisiologia , Camundongos Endogâmicos C57BL , Camundongos Knockout , Oxidopamina/administração & dosagem , Transtornos Parkinsonianos/induzido quimicamente , Transtornos Parkinsonianos/metabolismo , Transtornos Parkinsonianos/psicologia , Vesículas Sinápticas/metabolismo , Tirosina 3-Mono-Oxigenase/metabolismo , Proteína Vesicular 1 de Transporte de Glutamato/metabolismoRESUMO
The 16p11.2 600 kb BP4-BP5 deletion and duplication syndromes have been associated with developmental delay; autism spectrum disorders; and reciprocal effects on the body mass index, head circumference and brain volumes. Here, we explored these relationships using novel engineered mouse models carrying a deletion (Del/+) or a duplication (Dup/+) of the Sult1a1-Spn region homologous to the human 16p11.2 BP4-BP5 locus. On a C57BL/6N inbred genetic background, Del/+ mice exhibited reduced weight and impaired adipogenesis, hyperactivity, repetitive behaviors, and recognition memory deficits. In contrast, Dup/+ mice showed largely opposite phenotypes. On a F1 C57BL/6N × C3B hybrid genetic background, we also observed alterations in social interaction in the Del/+ and the Dup/+ animals, with other robust phenotypes affecting recognition memory and weight. To explore the dosage effect of the 16p11.2 genes on metabolism, Del/+ and Dup/+ models were challenged with high fat and high sugar diet, which revealed opposite energy imbalance. Transcriptomic analysis revealed that the majority of the genes located in the Sult1a1-Spn region were sensitive to dosage with a major effect on several pathways associated with neurocognitive and metabolic phenotypes. Whereas the behavioral consequence of the 16p11 region genetic dosage was similar in mice and humans with activity and memory alterations, the metabolic defects were opposite: adult Del/+ mice are lean in comparison to the human obese phenotype and the Dup/+ mice are overweight in comparison to the human underweight phenotype. Together, these data indicate that the dosage imbalance at the 16p11.2 locus perturbs the expression of modifiers outside the CNV that can modulate the penetrance, expressivity and direction of effects in both humans and mice.
Assuntos
Deleção Cromossômica , Duplicação Cromossômica/genética , Cognição , Adiposidade , Alelos , Animais , Arilsulfotransferase/genética , Arilsulfotransferase/metabolismo , Comportamento Animal , Peso Corporal , Encéfalo/metabolismo , Encéfalo/fisiopatologia , Cromossomos de Mamíferos/genética , Anormalidades Craniofaciais/genética , Dieta Hiperlipídica , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Rearranjo Gênico/genética , Hipocampo/fisiopatologia , Memória , Camundongos Endogâmicos C57BL , Atividade Motora , Fenótipo , Transmissão Sináptica/genética , Síndrome , DesmameRESUMO
We previously reported that the selective nociceptin orphanin peptide (NOP) receptor agonist, Ro64-6198, impairs mnemonic function through glutamatergic-dependent mechanisms. The aim of the current study was to determine whether the amnesic effects of Ro64-6198 involve a cholinergic component. The effects of systemic administration of Ro64-6198 (0.3 and 1 mg/kg, i.p.), the cholinergic nicotinic receptor antagonist, mecamylamine (0.1 and 1 mg/kg, s.c.), the cholinergic muscarinic receptor antagonist, scopolamine (0.1 and 0.3 mg/kg, s.c.), and the glutamatergic NMDA receptor antagonist, MK-801 (0.03 and 0.1 mg/kg, s.c.), were studied in the mouse object recognition task. All compounds tested were effective in disrupting formation of long-term (24-h delay) recognition memory. Drug interaction studies were then conducted to reveal the existence of functional interactions between NOP receptors and cholinergic and/or NMDA receptors. Co-administration of silent doses of Ro64-6198 (0.3 mg/kg) and MK-801 (0.01 mg/kg) produced clear-cut memory impairment. Similar synergistic effects were observed with the combination of mecamylamine (0.03 mg/kg) and scopolamine (0.1 mg/kg). In contrast, co-administration of Ro64-6198 (0.3 mg/kg) with either mecamylamine (0.03 and 0.1 mg/kg) or scopolamine (0.1 mg/kg) was without any effect on recognition memory. These findings suggest that NOP receptor may modulate memory formation through a functional interaction with glutamatergic but not cholinergic receptors.
Assuntos
Antagonistas Colinérgicos/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Imidazóis/farmacologia , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores Opioides/agonistas , Reconhecimento Psicológico/efeitos dos fármacos , Compostos de Espiro/farmacologia , Animais , Maleato de Dizocilpina/farmacologia , Interações Medicamentosas , Masculino , Mecamilamina/farmacologia , Camundongos , Escopolamina/farmacologia , Receptor de NociceptinaRESUMO
A subset of glutamatergic neurons in the forebrain uses labile Zn2+ as a co-transmitter alongside glutamate. Synaptic Zn2+ plays a key role in learning and memory processes, but its mechanisms of action remain poorly understood. Here, we used a knock-in (KI) mouse line carrying a point mutation at the GluN2A Zn2+ binding site that selectively eliminates zinc inhibition of NMDA receptors. Ablation of Zn2+-GluN2A binding improves spatial memory retention and contextual fear memory formation. Electrophysiological recording of hippocampal neurons in the CA1 area revealed a greater proportion of place cells and substantial place field remapping in KI mice compared to wildtype littermates. Persistent place cell remapping was also seen in KI mice upon repeated testing suggesting an enhanced ability to maintain a distinct representation across multiple overlapping experiences. Together, these findings reveal an original molecular mechanism through which synaptic Zn2+ negatively modulates spatial cognition by dampening GluN2A-containing NMDA receptor signaling.
RESUMO
In Parkinson's disease, nigrostriatal dopamine (DA) degeneration is commonly associated with motor symptomatology. However, non-motor symptoms affecting cognitive function, such as behavioural flexibility and inhibitory control may also appear early in the disease. Here we addressed the role of DA innervation of the dorsomedial striatum (DMS) in mediating these functions in 6-hydroxydopamine (6-OHDA)-lesioned mice using instrumental conditioning in various tasks. Behavioural flexibility was studied in a simple reversal task (nose-poke discrimination) or in reversal of a two-step sequence of actions (central followed by lateral nose-poke). Our results show that mild DA lesions of the DMS induces behavioural flexibility deficits in the sequential reversal learning only. In the first sessions following reversal of contingency, lesioned mice enhanced perseverative sequence of actions to the initial rewarded side then produced premature responses directly to the correct side omitting the central response, thus disrupting the two-step sequence of actions. These deficits may be linked to increased impulsivity as 6-OHDA-lesioned mice were unable to inhibit a previously learned motor response in a cued response inhibition task assessing proactive inhibitory control. Our findings show that partial DA denervation restricted to DMS impairs behavioural flexibility and proactive response inhibition in mice. Such striatal DA lesion may thus represent a valuable animal model for exploring deficits in executive control documented in early stage of Parkinson's disease.
Assuntos
Corpo Estriado , Dopamina , Animais , Denervação , Camundongos , Neostriado , Oxidopamina/toxicidadeRESUMO
Nociceptin/orphanin-FQ (N/OFQ) peptide and its receptor (NOP: N/OFQ opioid peptide receptor) are highly expressed in the hippocampus, but their functional role remains poorly understood. We recently showed that hippocampal N/OFQ inhibits learning and memory abilities in mice. Here, we investigated whether the endogenous peptide also regulated emotional responses at the level of the hippocampus. Bilateral infusions of the selective NOP receptor antagonist, UFP-101 (1-3 nmol/side), into the dorsal hippocampus produced antidepressant-like effects in the mouse forced swim and tail suspension tests comparable with those obtained with the prototypical antidepressant, fluoxetine (10-30 mg/kg, intraperitoneal). In the light-dark test, neither UFP-101 (1-3 nmol/side) nor N/OFQ peptide (1-3 nmol/side) modified anxiety measures when injected at behaviorally active doses in the dorsal hippocampus. These findings show a clear dissociation in the involvement of hippocampal N/OFQ system in anxiety- and despair-related behaviors. We conclude that the dorsal hippocampus is a brain region in which there is an important N/OFQ modulation of mnemonic processes and adaptive emotional responses associated to despair states.
Assuntos
Depressão/patologia , Hipocampo/metabolismo , Peptídeos Opioides/metabolismo , Análise de Variância , Animais , Comportamento Animal/efeitos dos fármacos , Adaptação à Escuridão/efeitos dos fármacos , Depressão/induzido quimicamente , Depressão/fisiopatologia , Modelos Animais de Doenças , Elevação dos Membros Posteriores/psicologia , Hipocampo/efeitos dos fármacos , Imidazóis/efeitos adversos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Peptídeos Opioides/efeitos adversos , Peptídeos Opioides/antagonistas & inibidores , Compostos de Espiro/efeitos adversos , Natação/psicologia , NociceptinaRESUMO
Strong evidence suggests a role for nociceptin/orphanin FQ (N/OFQ) neuropeptide and its receptor (NOP) in cognition. However, the signaling mechanisms underlying N/OFQ modulation of memory are less understood. Here, we show that intracerebroventricular or intrahippocampal infusions of N/OFQ impair long-term memory formation in the mouse object recognition task. The synthetic NOP receptor agonist, (1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one (Ro64-6198), administered systemically, also produced amnesic effects that were blocked by coinfusion of the NOP receptor antagonist, [Nphe1,Arg14,Lys15]nociceptin-NH2 (UFP-101), into the dorsal hippocampus. In contrast, Ro64-6198 had no effect on short-term memory or recall performances. Immunoblotting analysis revealed a strong suppressive action of Ro64-6198 on learning-induced upregulation of hippocampal extracellular signal-regulated kinase (ERK) phosphorylation, which is crucial for long-term information storage. Accordingly, pharmacological inhibition of ERK activation after systemic injection of SL327 [alpha-[amino[(4-aminophenyl)thio]methylene]-2-(trifluoromethyl)benzene acetonitrile], a selective inhibitor of the upstream kinase MEK (mitogen-activated protein kinase kinase), abolished long-term recognition memory formation. The noncompetitive NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine maleate (MK-801), given systemically, also suppressed ERK activation and disrupted recognition memory. In contrast, no effect of MK-801 was observed on recall, as for Ro64-6198. When administered concurrently at subthreshold doses, Ro64-6198 and MK-801 synergistically suppressed hippocampal ERK activation and impaired long-term memory formation. Under resting conditions, neither Ro64-6198 nor MK-801 affected spontaneous ERK activity in the hippocampus at the amnesic doses whereas at higher doses, only MK-801 had a suppressive effect. We conclude that N/OFQ-NOP receptor system negatively regulates long-term recognition memory formation through hippocampal ERK signaling mechanisms. This modulation may in part take place by inhibiting glutamatergic function at the NMDA receptor.
Assuntos
MAP Quinases Reguladas por Sinal Extracelular/fisiologia , Hipocampo/efeitos dos fármacos , Memória/efeitos dos fármacos , Peptídeos Opioides/farmacologia , Reconhecimento Visual de Modelos/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/fisiologia , Transdução de Sinais/fisiologia , Animais , Comportamento Animal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Interações Medicamentosas , Ativação Enzimática/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Fármacos Atuantes sobre Aminoácidos Excitatórios/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Testes Neuropsicológicos , Transdução de Sinais/efeitos dos fármacos , NociceptinaRESUMO
The present study investigated whether the selective nociceptin opioid peptide (NOP) receptor agonist, Ro64-6198, impairs acquisition of fear conditioning through glutamatergic mechanisms. Systemic administration of Ro64-6198 (0.3 and 1mg/kg) or the non-competitive NMDA receptor antagonist, MK-801 (0.03 and 0.1mg/kg) prior to conditioning severely impaired contextual but not cued fear learning in C57BL/6N mice. When administered together at sub-effective doses, Ro64-6198 (0.5mg/kg) and MK-801 (0.05mg/kg), synergistically impaired contextual fear learning, but left cued fear learning intact. We next used the immediate shock deficit paradigm (ISD) to examine the effects of Ro64-6198 and MK-801 on contextual memory formation in the absence of the foot-shock. As expected, naive mice that were shocked briefly after being placed in the training chamber displayed no contextual fear conditioning. This learning deficit was elevated by prior exposure of mice to the training context. Furthermore, administration of Ro64-6198 and MK-801, either separately at amnesic doses (1mg/kg and 0.1mg/kg, respectively) or concomitantly at sub-effective doses (0.5mg/kg and 0.05mg/kg, respectively) significantly reduced the facilitating effects of context preexposure. These findings demonstrate the existence of functional antagonism between NOP and NMDA receptors that predominantly contributes to modulation of conditioned fear learning which involves spatial-processing demands.
Assuntos
Condicionamento Psicológico/fisiologia , Medo , Ácido Glutâmico/metabolismo , Receptores Opioides/metabolismo , Analgésicos Opioides/farmacologia , Análise de Variância , Animais , Condicionamento Psicológico/efeitos dos fármacos , Sinais (Psicologia) , Maleato de Dizocilpina/farmacologia , Eletrochoque , Antagonistas de Aminoácidos Excitatórios/farmacologia , Imidazóis/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Morfina/farmacologia , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores Opioides/agonistas , Compostos de Espiro/farmacologia , Receptor de NociceptinaRESUMO
Establishing standard operating procedures (SOPs) as tools for the analysis of behavioral phenotypes is fundamental to mouse functional genomics. It is essential that the tests designed provide reliable measures of the process under investigation but most importantly that these are reproducible across both time and laboratories. For this reason, we devised and tested a set of SOPs to investigate mouse behavior. Five research centers were involved across France, Germany, Italy, and the UK in this study, as part of the EUMORPHIA program. All the procedures underwent a cross-validation experimental study to investigate the robustness of the designed protocols. Four inbred reference strains (C57BL/6J, C3HeB/FeJ, BALB/cByJ, 129S2/SvPas), reflecting their use as common background strains in mutagenesis programs, were analyzed to validate these tests. We demonstrate that the operating procedures employed, which includes open field, SHIRPA, grip-strength, rotarod, Y-maze, prepulse inhibition of acoustic startle response, and tail flick tests, generated reproducible results between laboratories for a number of the test output parameters. However, we also identified several uncontrolled variables that constitute confounding factors in behavioral phenotyping. The EUMORPHIA SOPs described here are an important start-point for the ongoing development of increasingly robust phenotyping platforms and their application in large-scale, multicentre mouse phenotyping programs.
Assuntos
Comportamento Animal/fisiologia , Técnicas de Laboratório Clínico , Cooperação Internacional , Animais , Laboratórios , Masculino , Aprendizagem em Labirinto , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Fenótipo , Reflexo de Sobressalto , Reprodutibilidade dos Testes , Teste de Desempenho do Rota-RodRESUMO
The aim of the present study was to clarify the role of nociceptin system in pain modulation. The effects of the synthetic nociceptin (NOP) receptor agonist, Ro64-6198 ((1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triaza-spiro[4.5]decan-4-one), on reactivity to acute noxious stimuli were assessed in C57BL/6N (B6) mice in tail-flick, hot-plate and shock threshold tests. The mu receptor agonist, morphine, was used in each study for comparison. In the tail-flick test, morphine (4 and 8 mg/kg, i.p.) produced analgesia, while Ro64-6198 (0.3, 1 and 3 mg/kg, i.p.) increased pain sensitivity. The effects of Ro64-6198 were seen in naïve but not in mice previously habituated to testing conditions, indicating that increased pain sensitivity may be due to inhibition of stress-induced analgesia. In the hot-plate and the shock threshold tests, Ro64-6198 produced analgesia in B6 mice, like morphine. These effects were reproduced in wild-type but not in NOP receptor knockout mice. Finally, when injected conjointly at subthreshold doses, Ro64-6198 (1 mg/kg) and morphine (1 mg/kg) acted in additive manner to reduce pain sensitivity in the hot-plate test. Together these results show that systemic activation of NOP receptors produced bidirectional changes in pain sensitivity depending on the experimental conditions. They also suggest that central NOP and mu receptors may inhibit reactivity to acute noxious stimuli via independent neural mechanisms.
Assuntos
Analgésicos Opioides/farmacologia , Imidazóis/farmacologia , Morfina/farmacologia , Dor/tratamento farmacológico , Compostos de Espiro/farmacologia , Analgésicos Opioides/administração & dosagem , Animais , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Temperatura Alta , Imidazóis/administração & dosagem , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Morfina/administração & dosagem , Medição da Dor/métodos , Limiar da Dor/efeitos dos fármacos , Tempo de Reação/efeitos dos fármacos , Receptores Opioides/agonistas , Receptores Opioides/genética , Receptores Opioides mu/agonistas , Compostos de Espiro/administração & dosagem , Estresse Fisiológico , Cauda , Receptor de NociceptinaRESUMO
The present study examined the developmental course of the age-related hearing loss and its consequences on the expression of acoustic startle reflex (ASR) and prepulse inhibition (PPI) generated by white-noise bursts in 129S2/SvPas (129) and C57BL/6J (C57) mouse strains and their F(1) hybrids. Auditory brainstem responses (ABR), ASR and PPI were assessed at various time points: 6, 28, 41 and 94 weeks. Both parental strains showed marked ABR threshold shifts with age, with C57 mice having the most pronounced deficits. By contrast, the hybrids displayed only minor hearing loss with age. The time courses of ASR and PPI varied considerably between the mouse strains. From 6 to 41 weeks of age, ASR and PPI elicited by weak stimuli (70-90dB) increased in C57 mice, whereas the startle responses to intense stimuli (95-120dB) declined progressively. In 129 and hybrid mice, PPI levels remained relatively stable during the first year, but a progressive increase of ASR was observed in the hybrids for intense stimuli (95-120dB). When animals reached 94 weeks of age, marked deterioration of ASR was observed in all strains, while deficits in PPI were only seen in 129 and C57 mice. These findings show that the time course and the severity of the hearing loss vary considerably between 129, C57 strains and their hybrids, thus suggesting a marked heterogeneity in the genetic mechanisms underlying deafness in mice. They also demonstrate that the age-related hearing loss may have complex consequences on auditory behavioral performances depending of the severity of the deficits, the genetic background as well as the stimuli parameters.
Assuntos
Envelhecimento/fisiologia , Limiar Auditivo/fisiologia , Perda Auditiva , Inibição Neural/fisiologia , Presbiacusia/fisiopatologia , Reflexo de Sobressalto/fisiologia , Estimulação Acústica , Animais , Aprendizagem por Associação/fisiologia , Perda Auditiva/genética , Perda Auditiva/fisiopatologia , Hibridização Genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Inibição Neural/genética , Presbiacusia/genética , Reflexo de Sobressalto/genética , Especificidade da Espécie , Estatísticas não ParamétricasRESUMO
NMDA receptor hypofunction has been implicated in the pathophysiology of schizophrenia, and pharmacological and genetic approaches have been used to model such dysfunction. We previously have described two mouse lines carrying point mutations in the NMDA receptor glycine binding site, Grin1(D481N) and Grin1(K483Q), which exhibit 5- and 86-fold reductions in receptor glycine affinity, respectively. Grin1(D481N) animals exhibit a relatively mild phenotype compatible with a moderate reduction in NMDA receptor function, whereas Grin1(K483Q) animals die shortly after birth. In this study we have characterized compound heterozygote Grin1(D481N/K483Q) mice, which are viable and exhibited biphasic NMDA receptor glycine affinities compatible with the presence of each of the two mutated alleles. Grin1(D481N/K483Q) mice exhibited a marked NMDA receptor hypofunction revealed by deficits in hippocampal long-term potentiation, which were rescued by the glycine site agonist d-serine, which also facilitated NMDA synaptic currents in mutant, but not in wild-type, mice. Analysis of striatal monoamine levels revealed an apparent dopaminergic and serotonergic hyperfunction. Behaviorally, Grin1(D481N/K483Q) mice were insensitive to acute dizocilpine pretreatment and exhibited increased startle response but normal prepulse inhibition. Most strikingly, mutant mice exhibited a sustained, nonhabituating hyperactivity and increased stereotyped behavior that were resistant to suppression by antipsychotics and the benzodiazepine site agonist Zolpidem. They also displayed a disruption of nest building behavior and were unable to perform a cued learning paradigm in the Morris water maze. We speculate that the severity of NMDA receptor hypofunction in these mice may account for their profound behavioral phenotype and insensitivity to antipsychotics.
Assuntos
Resistência a Medicamentos/genética , Glicina/metabolismo , Hipercinese/genética , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Antipsicóticos/farmacologia , Comportamento Animal/efeitos dos fármacos , Sítios de Ligação/genética , Ligação Competitiva/efeitos dos fármacos , Ligação Competitiva/genética , Aminas Biogênicas/metabolismo , Corpo Estriado/química , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Relação Dose-Resposta a Droga , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/genética , Agonistas GABAérgicos/farmacologia , Marcação de Genes , Ácido Glutâmico/farmacocinética , Glicina/agonistas , Glicina/farmacocinética , Heterozigoto , Hipocampo/fisiopatologia , Hipercinese/fisiopatologia , Técnicas In Vitro , Potenciação de Longa Duração/genética , Camundongos , Camundongos Mutantes Neurológicos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Técnicas de Patch-Clamp , Fenótipo , Mutação Puntual , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Serina/análogos & derivados , Serina/farmacologia , Estereoisomerismo , Comportamento Estereotipado/efeitos dos fármacosRESUMO
Transgenic mice, expressing mutant beta-amyloid precursor proteins (betaAPPs), have lead to a better understanding of the pathophysiological processes in Alzheimer's disease (AD). In many of these models, however, the temporal development of cognitive decline and the relationship to Abeta deposition and inflammation are unclear. We now report a novel transgenic mouse line, PS2APP (PS2N141I x APPswe), which develops a severe cerebral amyloidosis in discrete brain regions, and present a cross-sectional analysis of these mice at 4, 8, 12, and 16 months of age. Each age cohort was investigated for changes in behavior, electrophysiology of synapse efficacy, ELISA-determined Abeta load, histopathology, and in immunoelectron microscopy. Cognitive deficits were first observed at 8 months when Abeta deposits and inflammation were restricted to discrete brain regions, namely the subiculum and frontolateral (motor and orbital) cortex. As early as 5 months, electron microscopy revealed the presence, in these regions, of pre-plaque, immunogold-labeled extracellular fibrillar Abeta. At the same age, increased levels of insoluble Abeta were detected by ELISA, with Abeta1-40 levels exceeding those of Abeta1-42. Further cognitive decline occurred in an age-related manner, and this was accompanied by the spread of amyloidosis to ultimately affect not only neo- and limbic cortices, but also thalamic and pontine nuclei. Dentate gyrus post-tetanic potentiation was significantly attenuated at 17 months, and there were also significant differences in paired-pulse parameters. This systematic cross-sectional study of the behavioral and pathological changes in the PS2APP mouse indicates that it develops age-related cognitive decline associated with severe amyloidosis and inflammation in discrete brain regions and therefore is suitable for testing a range of potential symptomatic and disease-modifying therapies for AD.
Assuntos
Precursor de Proteína beta-Amiloide/biossíntese , Amiloidose/fisiopatologia , Encéfalo/metabolismo , Transtornos Cognitivos/fisiopatologia , Proteínas de Membrana/biossíntese , Fatores Etários , Peptídeos beta-Amiloides/análise , Peptídeos beta-Amiloides/biossíntese , Precursor de Proteína beta-Amiloide/genética , Amiloidose/complicações , Amiloidose/patologia , Animais , Comportamento Animal , Encéfalo/patologia , Química Encefálica , Transtornos Cognitivos/complicações , Transtornos Cognitivos/patologia , Estudos Transversais , Cruzamentos Genéticos , Modelos Animais de Doenças , Progressão da Doença , Hipocampo/fisiopatologia , Humanos , Técnicas In Vitro , Masculino , Aprendizagem em Labirinto , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos , Camundongos Transgênicos , Microscopia Imunoeletrônica , Mutação , Plasticidade Neuronal/genética , Presenilina-2 , Transmissão Sináptica/genéticaRESUMO
BACKGROUND: The delta opioid receptor (DOR) is broadly expressed throughout the nervous system; it regulates chronic pain, emotional responses, motivation, and memory. Neural circuits underlying DOR activities have been poorly explored by genetic approaches. We used conditional mouse mutagenesis to elucidate receptor function in GABAergic neurons of the forebrain. METHODS: We characterized DOR distribution in the brain of Dlx5/6-CreXOprd1(fl/fl) (Dlx-DOR) mice and tested main central DOR functions through behavioral testing. RESULTS: The DOR proteins were strongly deleted in olfactory bulb and striatum and remained intact in cortex and basolateral amygdala. Olfactory perception, circadian activity, and despair-like behaviors were unchanged. In contrast, locomotor stimulant effects of SNC80 (DOR agonist) and SKF81297 (D1 agonist) were abolished and increased, respectively. The Dlx-DOR mice showed lower levels of anxiety in the elevated plus maze, opposing the known high anxiety in constitutive DOR knockout animals. Also, Dlx-DOR mice reached the food more rapidly in a novelty suppressed feeding task, despite their lower motivation for food reward observed in an operant paradigm. Finally, c-fos protein staining after novelty suppressed feeding was strongly reduced in amygdala, concordant with the low anxiety phenotype of Dlx-DOR mice. CONCLUSIONS: We demonstrate that DORs expressed in the forebrain mediate the described locomotor effect of SNC80 and inhibit D1-stimulated hyperactivity. Our data also reveal an unanticipated anxiogenic role for this particular DOR subpopulation, with a potential novel adaptive role. In emotional responses, DORs exert dual anxiolytic and anxiogenic roles, both of which may have implications in the area of anxiety disorders.
Assuntos
Ansiedade/fisiopatologia , Neurônios GABAérgicos/metabolismo , Prosencéfalo/metabolismo , Receptores Opioides delta/metabolismo , Animais , Comportamento Animal/fisiologia , Benzamidas/farmacologia , Benzazepinas/farmacologia , Encéfalo/metabolismo , Corpo Estriado/metabolismo , Agonistas de Dopamina/farmacologia , Feminino , Masculino , Camundongos , Camundongos Knockout , Motivação/fisiologia , Atividade Motora/efeitos dos fármacos , Bulbo Olfatório/metabolismo , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , RNA Mensageiro/metabolismo , Receptores de Dopamina D1/agonistas , Receptores Opioides delta/agonistas , Receptores Opioides delta/análise , Receptores Opioides delta/genéticaRESUMO
RATIONALE AND OBJECTIVES: Recognition memory is an important aspect of human declarative memory and is one of the routine memory abilities altered in patients with amnestic syndrome and Alzheimer's disease. In rodents, recognition memory has been most widely assessed using the novel object preference paradigm, which exploits the spontaneous preference that animals display for novel objects. Here, we used nose-poke units instead of objects to design a simple automated method for assessing context recognition memory in mice. METHODS: In the acquisition trial, mice are exposed for the first time to an operant chamber with one blinking nose-poke unit. In the choice session, a novel nonblinking nose-poke unit is inserted into an empty spatial location and the number of nose poking dedicated to each set of nose-poke unit is used as an index of recognition memory. RESULTS: We report that recognition performance varies as a function of the length of the acquisition period and the retention delay and is sensitive to conventional amnestic treatments. By manipulating the features of the operant chamber during a brief retrieval episode (3-min long), we further demonstrate that reconsolidation of the original contextual memory depends on the magnitude and the type of environmental changes introduced into the familiar spatial environment. CONCLUSIONS: These results show that the nose-poke recognition task provides a rapid and reliable way for assessing context recognition memory in mice and offers new possibilities for the deciphering of the brain mechanisms governing the reconsolidation process.
Assuntos
Comportamento Animal/fisiologia , Testes Neuropsicológicos , Reconhecimento Psicológico/fisiologia , Animais , Masculino , Memória , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Addiction is a chronic disorder involving recurring intoxication, withdrawal, and craving episodes. Escaping this vicious cycle requires maintenance of abstinence for extended periods of time and is a true challenge for addicted individuals. The emergence of depressive symptoms, including social withdrawal, is considered a main cause for relapse, but underlying mechanisms are poorly understood. Here we establish a mouse model of protracted abstinence to heroin, a major abused opiate, where both emotional and working memory deficits unfold. We show that delta and kappa opioid receptor (DOR and KOR, respectively) knockout mice develop either stronger or reduced emotional disruption during heroin abstinence, establishing DOR and KOR activities as protective and vulnerability factors, respectively, that regulate the severity of abstinence. Further, we found that chronic treatment with the antidepressant drug fluoxetine prevents emergence of low sociability, with no impact on the working memory deficit, implicating serotonergic mechanisms predominantly in emotional aspects of abstinence symptoms. Finally, targeting the main serotonergic brain structure, we show that gene knockout of mu opioid receptors (MORs) in the dorsal raphe nucleus (DRN) before heroin exposure abolishes the development of social withdrawal. This is the first result demonstrating that intermittent chronic MOR activation at the level of DRN represents an essential mechanism contributing to low sociability during protracted heroin abstinence. Altogether, our findings reveal crucial and distinct roles for all three opioid receptors in the development of emotional alterations that follow a history of heroin exposure and open the way towards understanding opioid system-mediated serotonin homeostasis in heroin abuse.
Assuntos
Dependência de Heroína/fisiopatologia , Receptores Opioides kappa/metabolismo , Receptores Opioides mu/metabolismo , Comportamento Social , Síndrome de Abstinência a Substâncias/fisiopatologia , Animais , Antidepressivos de Segunda Geração/farmacologia , Depressão/metabolismo , Modelos Animais de Doenças , Núcleo Dorsal da Rafe/efeitos dos fármacos , Núcleo Dorsal da Rafe/metabolismo , Fluoxetina/farmacologia , Heroína/farmacologia , Dependência de Heroína/psicologia , Masculino , Transtornos da Memória/fisiopatologia , Memória de Curto Prazo/efeitos dos fármacos , Memória de Curto Prazo/fisiologia , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Camundongos Knockout , Entorpecentes/farmacologia , Receptores Opioides kappa/genética , Receptores Opioides mu/genética , Memória Espacial/efeitos dos fármacos , Memória Espacial/fisiologia , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Síndrome de Abstinência a Substâncias/psicologiaRESUMO
Nociceptin/orphanin FQ (N/OFQ) peptide and its receptor (NOP receptor) have been implicated in a host of brain functions and diseases, but the contribution of this neuropeptide system to behavioral processes of relevance to psychosis has not been investigated. We examined the effect of the NOP receptor antagonists, Compound 24 and J-113397, and the synthetic agonist, Ro64-6198, on time function (2-2000 ms prepulse-pulse intervals) of acoustic (80 dB/10 ms prepulse) and visual (1000 Lux/20 ms prepulse) prepulse inhibition of startle reflex (PPI), a preattentive sensory filtering mechanism that is central to perceptual and mental integration. The effects of the dopamine D1-like receptor agonist, SKF-81297, the D2-like receptor agonist, quinelorane, and the mixed D1/D2 agonist, apomorphine, were studied for comparison. When acoustic stimulus was used as prepulse, BALB/cByJ mice displayed a monotonic time function of PPI, and consistent with previous studies, apomorphine and SKF-81279 induced PPI impairment, whereas quinelorane had no effect. None of the NOP receptor ligands was effective on acoustic PPI. When flash light was used as prepulse, BALB/cByJ mice displayed a bell-shaped time function of PPI and all dopamine agonists were active. Ro64-6198 was also effective in reducing visual PPI. NOP receptor antagonists showed no activity but blocked disruptive effect of Ro64-6198. Finally, coadministration of the typical antipsychotic, haloperidol, attenuated PPI impairment induced by Ro64-6198, revealing involvement of a dopaminergic component. These findings show that pharmacological stimulation of NOP or dopamine D2-like receptors is more potent in disrupting visual than acoustic PPI in mice, whereas D1-like receptor activation disrupts both. They further suggest that dysfunction of N/OFQ transmission may be implicated in the pathogenesis of psychotic manifestations.
Assuntos
Agonistas de Dopamina/farmacologia , Receptores Dopaminérgicos/fisiologia , Receptores Opioides/fisiologia , Filtro Sensorial/fisiologia , Estimulação Acústica/métodos , Animais , Benzimidazóis/farmacologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Haloperidol/farmacologia , Imidazóis/antagonistas & inibidores , Imidazóis/farmacologia , Lisina/análogos & derivados , Lisina/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Antagonistas de Entorpecentes , Estimulação Luminosa/métodos , Piperidinas/farmacologia , Receptores Opioides/agonistas , Reflexo de Sobressalto/efeitos dos fármacos , Reflexo de Sobressalto/fisiologia , Filtro Sensorial/efeitos dos fármacos , Compostos de Espiro/antagonistas & inibidores , Compostos de Espiro/farmacologia , Receptor de NociceptinaRESUMO
BACKGROUND: Opiate abuse is a chronic relapsing disorder, and maintaining prolonged abstinence remains a major challenge. Protracted abstinence is characterized by lowered mood, and clinical studies show elevated comorbidity between addiction and depressive disorders. At present, their relationship remains unclear and has been little studied in animal models. Here we investigated emotional alterations during protracted abstinence, in mice with a history of chronic morphine exposure. METHODS: C57BL6J mice were exposed to a chronic intermittent escalating morphine regimen (20-100 mg/kg). Physical dependence (naloxone-precipitated withdrawal), despair-related behaviors (tail suspension test), and social behaviors were examined after 1 or 4 weeks of abstinence. Stress hormones and forebrain bioamine levels were analyzed at the end of morphine regimen and after 4 weeks of abstinence. Finally, we examined the effects of chronic fluoxetine during abstinence on morphine-induced behavioral deficits. RESULTS: Acute naloxone-induced withdrawal was clearly measurable after 1 week, and became undetectable after 4 weeks. In contrast, social and despair-related behaviors were unchanged after 1 week, but low sociability and despair-like behavior became significant after 4 weeks. Chronic morphine regimen increased both corticosterone levels and forebrain serotonin turnover, but only serotonergic activity in the dorsal raphe remained impaired after 4 weeks. Remarkably, chronic fluoxetine prevented depressive-like behavioral deficits in 4-week abstinent mice. CONCLUSIONS: During protracted abstinence, the immediate consequences of morphine exposure attenuate, whereas fluoxetine-sensitive emotional alterations strengthen with time. Our study establishes a direct link between morphine abstinence and depressive-like symptoms and strongly suggests that serotonin dysfunction represents a main mechanism contributing to mood disorders in opiate abstinence.