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Leucine-rich repeat kinase 2, synaptic morphology and motor behavior
No full textMutations in the leucine-rich repeat kinase 2 (LRRK2) gene are known to cause late-onset, familial forms of Parkinson’s Disease, with prevalence up to 40% in specific populations. These mutations are also linked to sporadic PD, highlighting the importance of the related protein in the development of the disease.
LRRK2 is a large, complex, multi-domain protein, with two main enzymatic activities: a GTPase domain (bearing three pathogenic mutations) and a kinase domain, in which the most common mutation (G2019S) is found.
Even though the precise cellular functions of LRRK2 are not known, LRRK2 has been proposed to take part in key signaling pathways, ultimately governing cellular functions such as synaptic transmission, synaptic vesicle dynamics, autophagy and membrane-to-Golgi trafficking.
Major efforts have been dedicated to development and characterization of animal models of LRRK2-induced parkinsonism. However, transgenic models reported so far failed in showing parkinsonian phenotype and neuropathology.
In this work, we used three different mouse lines (non-transgenic, BAC hLRRK2-G2019S and LRRK2 knockout) to explore spontaneous and physiologically-stimulated motor behavior as well motor responses to dopaminergic compounds. We found that the G2019S mutation leads to motor impairment which is responsive to dopamine agonists, while ablation of the protein causes hyperactivity and reduced anxious-like behavior. Moreover, mice expressing the G2019S mutation and knockout mice showed opposite responses to dopamine receptor stimulation.
In order to investigate the role of endogenous LRRK2 on synaptic morphology and connectivity, we co-cultured striatal medium spiny neurons (MSN) and cortical neurons and applied the LRRK2 kinase inhibitor LRRK2-IN1. We observed a tendency for an increased presynaptic drive towards MSNs and reduction of their postsynaptic receptiveness.
These results show that LRRK2 is profoundly involved in regulation of motor and non-motor behavior, with pathogenic mutation leading to the development of a parkinsonian phenotype. This role of LRRK2 is intimately associated with dopamine machinery. We also propose LRRK2 to participate in the maintenance and regulation of cortico-striatal synapses in vitro
Stimulation of delta opioid receptors located in substantia nigra reticulata but not globus pallidus or striatum restores motor activity in 6-hydroxydopamine lesioned rats. New insights into the role of delta receptors in parkinsonism
No full textThe delta opioid peptide (DOP) receptor has been proposed as a target in the symptomatic therapy of Parkinson’s disease. However, the circuitry underlying the antiparkinsonian action of DOP receptor agonists and their site of action have never been adequately investigated. Systemic administration of the DOP receptor agonist (+)-4-[(αR)-α-(2S,5R)-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide (SNC-80) attenuated akinesia/bradykinesia and improved motor activity in 6-hydroxydopamine hemilesioned rats. Opposite effects were produced by the selective DOP receptor antagonist naltrindole, suggesting that endogenous enkephalins tonically sustain movement under parkinsonian conditions. Microdialysis revealed that SNC-80 reduced GABA release in globus pallidus while naltrindole elevated it. Moreover, SNC-80 reduced GABA and glutamate release in substantia nigra reticulata whereas naltrindole reduced GABA without affecting glutamate release. The bar test coupled to microdialysis showed that perfusion with naltrindole in substantia nigra reticulata but not globus pallidus or striatum prevented the antiakinetic effect of systemic SNC-80 and its neurochemical correlates. Consistently, microinjections of SNC-80 into substantia nigra reticulata or bicuculline in globus pallidus attenuated parkinsonian-like symptoms while SNC-80 microinjections in globus pallidus or striatum were ineffective. This study demonstrates that nigral DOP receptors mediate antiparkinsonian actions of SNC-80 and challenges the common view that DOP receptor agonists solely attenuate parkinsonism via pallidal mechanisms
Dopamine–nociceptin/orphanin FQ interactions in the substantia nigra reticulata of hemiparkinsonian rats: Involvement of D2/D3 receptors and impact on nigro-thalamic neurons and motor activity
No full textNociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor antagonists proved to be effective in alleviating experimental parkinsonism. Nonetheless, loss of effectiveness or even worsening of parkinsonian symptoms have been observed at high doses. With the aim of clarifying the circuitry underlying the dual action of NOP receptor antagonists and the role of endogenous dopamine, the NOP receptor antagonist 1-benzyl-N-[3-[spiroisobenzofuran-1(3H),4'-piperidin-1-yl]propyl]pyrrolidine-2-carboxamide (Compound 24) and the D2/D3 receptor antagonist raclopride were used in 6-hydroxydopamine hemilesioned rats. Systemically administered Compound 24 improved motor activity in the 0.1-10mg/kg dose range being ineffective at 30mg/kg. To confirm NOP selectivity, Compound 24 improved motor performance in wild-type mice at 1 and 10mg/kg and inhibited it at 60mg/kg, being ineffective in NOP receptor knockout mice. To prove that the bell-shaped profile was mediated by nigral NOP receptors, reverse dialysis of Compound 24 (0.03μM) in substantia nigra reticulata ameliorated akinesia whereas Compound 24 (3μM) was ineffective. To demonstrate that motor responses were mediated by tuning inhibitory and excitatory inputs to nigro-thalamic neurons, the low concentration elevated GABA and reduced glutamate in substantia nigra, simultaneously reducing GABA levels in ventro-medial thalamus. Conversely, the higher concentration reduced nigral and elevated thalamic GABA, without affecting nigral glutamate levels. Co-perfusion with raclopride (1μM) abolished the antiakinetic action of Compound 24 (0.03μM) and turned the ineffectiveness of Compound 24 (3μM) into an antiakinetic effect. The low concentration reduced nigral but did not affect thalamic GABA whereas the higher concentration elevated nigral and reduced thalamic GABA. Neither concentration affected nigral glutamate. We conclude that dual motor effects of Compound 24 in hemiparkinsonian rats are accomplished through blockade of nigral NOP receptors resulting in opposite modulation of nigro-thalamic neurons. Endogenous dopamine contributes to these responses affecting the level of GABAergic inhibition of the nigral output via D2/D3 receptors. © 2010 Elsevier Inc
Stimulation of delta opioid receptors located in substantia nigra reticulata but not globus pallidus or striatum restores motor activity in 6‐hydroxydopamine lesioned rats: new insights into the role of delta receptors in parkinsonism
No full textThe delta opioid peptide (DOP) receptor has been proposed as a target in the symptomatic therapy of Parkinson’s disease. However, the circuitry underlying the antiparkinsonian action of DOP receptor agonists and their site of action have never been adequately investigated. Systemic administration of the DOP receptor agonist (+)-4-[(αR)-α-(2S,5R)-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide (SNC-80) attenuated akinesia/bradykinesia and improved motor activity in 6-hydroxydopamine hemilesioned rats. Opposite effects were produced by the selective DOP receptor antagonist naltrindole, suggesting that endogenous enkephalins tonically sustain movement under parkinsonian conditions. Microdialysis revealed that SNC-80 reduced GABA release in globus pallidus while naltrindole elevated it. Moreover, SNC-80 reduced GABA and glutamate release in substantia nigra reticulata whereas naltrindole reduced GABA without affecting glutamate release. The bar test coupled to microdialysis showed that perfusion with naltrindole in substantia nigra reticulata but not globus pallidus or striatum prevented the antiakinetic effect of systemic SNC-80 and its neurochemical correlates. Consistently, microinjections of SNC-80 into substantia nigra reticulata or bicuculline in globus pallidus attenuated parkinsonian-like symptoms while SNC-80 microinjections in globus pallidus or striatum were ineffective. This study demonstrates that nigral DOP receptors mediate antiparkinsonian actions of SNC-80 and challenges the common view that DOP receptor agonists solely attenuate parkinsonism via pallidal mechanisms
Stimulation of Delta Opioid Receptor and Blockade of Nociceptin/Orphanin FQ Receptor Synergistically Attenuate Parkinsonism
No full textDelta opioid peptide (DOP) receptors are considered a therapeutic target in Parkinson’s disease, although the use of DOP agonists may be
limited by side effects, including convulsions. To circumvent this issue, we evaluated whether blockade of nociceptin/orphanin FQ
(N/OFQ) tone potentiated the antiparkinsonian effects of DOP agonists, thus allowing for reduction of their dosage. Systemic
administration of the N/OFQ receptor (NOP) antagonist J-113397 [(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-
ethyl-1,3-dihydro-2H benzimidazol-2-one] and the DOP receptor agonist SNC-80 [()-4-[(R)--(2S,5R)-allyl-2,5-dimethyl-1-
piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide] revealed synergistic attenuation of motor deficits in 6-hydroxydopamine
hemilesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice. In this model, repeated administration of the combination
produced reproducible antiparkinsonian effects and was not associated with rescued striatal dopamine terminals. Microdialysis studies revealed
that either systemic administration or local intranigral perfusion of J-113397 and SNC-80 led to the enhancement of nigral GABA,
reduction of nigral Glu, and reduction of thalamic GABA levels, consistent with the view that NOP receptor blockade and DOP
receptor stimulation caused synergistic overinhibition of nigro-thalamic GABA neurons. Whole-cell recording of GABA neurons
in nigral slices confirmed that NOP receptor blockade enhanced the DOP receptor-induced effect on IPSCs via presynaptic mechanisms.
Finally, SNC-80 more potently stimulated stepping activity in mice lacking the NOP receptor than wild-type controls,
confirming the in vivo occurrence of an NOP–DOP receptor interaction. We conclude that endogenous N/OFQ functionally opposes
DOP transmission in substantia nigra reticulata and that NOP receptor antagonists might be used in combination with DOP
receptor agonists to reduce their dosage while maintaining their full therapeutic efficacy
Pharmacological profile and antiparkinsonian properties of the novel nociceptin/orphanin FQ receptor antagonist 1-[1-Cyclooctylmethyl-5-(1-hydroxy-1-methyl-ethyl)-1,2,3,6-tetrahydro-pyridin-4-yl]-3-ethyl-1,3-dihydro-benzoimidazol-2-one (GF-4)
No full textIn this study we provided a pharmacological characterization of the recently synthesized nociceptin/
orphanin FQ (N/OFQ) peptide receptor (NOP) antagonist 1-[1-Cyclooctylmethyl-5-(1-hydroxy-
1-methyl-ethyl)-1,2,3,6-tetrahydro-pyridin-4-yl]-3-ethyl-1,3-dihydro-benzoimidazol-2-one (GF-4) and
investigated its antiparkinsonian properties. GF-4 inhibited N/OFQ binding to CHOhNOP cell membranes
(pKi 7.46), and antagonized N/OFQ effects in a calcium mobilization assay and electrically stimulated
isolated tissues (pKB 7.27–7.82), showing a ∼5-fold selectivity over classical opioid receptors. In vivo,
GF-4 dually modulated stepping activity in wild-type mice, causing facilitation in the 0.01–10 mg/kg
dose range and inhibition at 30 mg/kg. These effects were mediated by NOP receptors since GF-4 was
ineffective in NOP receptor knock-out mice. Antiparkinsonian properties of GF-4 were investigated in
6-hydroxydopamine hemilesioned rats. GF-4 ameliorated akinesia, bradykinesia and overall gait ability
in the 0.1–10 mg/kg dose range, but inhibited motor activity at 30 mg/kg. To investigate the circuitry
underlying motor facilitating and inhibitory effects of GF-4, microdialysis coupled to behavioral testing
(akinesia test) was performed. An anti-akinetic dose of GF-4 (1 mg/kg) reduced glutamate (GLU) and
enhanced GABA release in SNr, while the pro-akinetic dose of GF-4 (30 mg/kg) evoked opposite effects.
Moreover, the anti-akinetic dose of GF-4 reduced GABA and increased GLU release in ventro-medial thalamus,
the pro-akinetic dose decreasing GABA without affecting GLU release in this area. We conclude
that GF-4 is an effective NOP receptor antagonist able to attenuate parkinsonian-like symptoms in vivo
via inhibition of the nigro-thalamic pathway
Stimulation of Delta Opioid Receptor and Blockade of Nociceptin/Orphanin FQ Receptor Synergistically Attenuate Parkinsonism
No full textDelta opioid peptide (DOP) receptors are considered a therapeutic target in Parkinson’s disease, although the use of DOP agonists may be
limited by side effects, including convulsions. To circumvent this issue, we evaluated whether blockade of nociceptin/orphanin FQ
(N/OFQ) tone potentiated the antiparkinsonian effects of DOP agonists, thus allowing for reduction of their dosage. Systemic
administration of the N/OFQ receptor (NOP) antagonist J-113397 [(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-
ethyl-1,3-dihydro-2H benzimidazol-2-one] and the DOP receptor agonist SNC-80 [()-4-[(R)--(2S,5R)-allyl-2,5-dimethyl-1-
piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide] revealed synergistic attenuation of motor deficits in 6-hydroxydopamine
hemilesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice. In this model, repeated administration of the combination
produced reproducible antiparkinsonian effects and was not associated with rescued striatal dopamine terminals. Microdialysis studies revealed
that either systemic administration or local intranigral perfusion of J-113397 and SNC-80 led to the enhancement of nigral GABA,
reduction of nigral Glu, and reduction of thalamic GABA levels, consistent with the view that NOP receptor blockade and DOP
receptor stimulation caused synergistic overinhibition of nigro-thalamic GABA neurons. Whole-cell recording of GABA neurons
in nigral slices confirmed that NOP receptor blockade enhanced the DOP receptor-induced effect on IPSCs via presynaptic mechanisms.
Finally, SNC-80 more potently stimulated stepping activity in mice lacking the NOP receptor than wild-type controls,
confirming the in vivo occurrence of an NOP–DOP receptor interaction. We conclude that endogenous N/OFQ functionally opposes
DOP transmission in substantia nigra reticulata and that NOP receptor antagonists might be used in combination with DOP
receptor agonists to reduce their dosage while maintaining their full therapeutic efficacy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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