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1.
Mol Pharmacol ; 98(4): 303-313, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32873746

RESUMO

Muscimol is a psychoactive isoxazole derived from the mushroom Amanita muscaria and a potent orthosteric agonist of the GABAA receptor. The binding of [3H]muscimol has been used to evaluate the distribution of GABAA receptors in the brain, and studies of modulation of [3H]muscimol binding by allosteric GABAergic modulators such as barbiturates and steroid anesthetics have provided insight into the modes of action of these drugs on the GABAA receptor. It has, however, not been feasible to directly apply interaction parameters derived from functional studies to describe the binding of muscimol to the receptor. Here, we employed the Monod-Wyman-Changeux concerted transition model to analyze muscimol binding isotherms. We show that the binding isotherms from recombinant α1ß3 GABAA receptors can be qualitatively predicted using electrophysiological data pertaining to properties of receptor activation and desensitization in the presence of muscimol. The model predicts enhancement of [3H]muscimol binding in the presence of the steroids allopregnanolone and pregnenolone sulfate, although the steroids interact with distinct sites and either enhance (allopregnanolone) or reduce (pregnenolone sulfate) receptor function. We infer that the concerted transition model can be used to link radioligand binding and electrophysiological data. SIGNIFICANCE STATEMENT: The study employs a three-state resting-active-desensitized model to link radioligand binding and electrophysiological data. We show that the binding isotherms can be qualitatively predicted using parameters estimated in electrophysiological experiments and that the model accurately predicts the enhancement of [3H]muscimol binding in the presence of the potentiating steroid allopregnanolone and the inhibitory steroid pregnenolone sulfate.


Assuntos
Agonistas de Receptores de GABA-A/farmacologia , Muscimol/farmacologia , Receptores de GABA-A/metabolismo , Esteroides/farmacologia , Regulação Alostérica/efeitos dos fármacos , Sítios de Ligação , Células HEK293 , Humanos , Complexos Multiproteicos/química , Complexos Multiproteicos/genética , Muscimol/química , Pregnanolona/farmacologia , Pregnenolona/farmacologia , Receptores de GABA-A/química , Receptores de GABA-A/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Trítio/química
2.
Psychopharmacology (Berl) ; 237(7): 2161-2172, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32363439

RESUMO

The ability to discriminate between danger and safety is crucial for survival across species. Whereas danger signals predict the onset of a potentially threatening event, safety signals indicate the non-occurrence of an aversive event, thereby reducing fear and stress responses. While the neural basis of conditioned safety remains to be elucidated, fear extinction studies provide evidence that the infralimbic cortex (IL) modulates fear inhibition. In the current study, the IL was temporarily inactivated with local muscimol injections in male and female rats. The effect of IL inactivation on the acquisition and expression of conditioned safety was investigated utilizing the startle response. Temporary inactivation of the IL prior to conditioning did not affect the acquisition of conditioned safety, whereas IL inactivation during the expression test completely blocked the expression of conditioned safety in male and female rats. Inactivation of the neighboring prelimbic (PL) cortex during the expression test did not affect the expression of safety memory. Our findings suggest that the IL is a critical brain region for the expression of safety memory. Because patients suffering from anxiety disorders are often unable to make use of safety cues to inhibit fear, the present findings are of clinical relevance and could potentially contribute to therapy optimization of anxiety-related psychiatric disorders.


Assuntos
Condicionamento Clássico/fisiologia , Medo/fisiologia , Inibição Psicológica , Memória/fisiologia , Córtex Pré-Frontal/metabolismo , Reflexo de Sobressalto/fisiologia , Animais , Condicionamento Clássico/efeitos dos fármacos , Extinção Psicológica/efeitos dos fármacos , Extinção Psicológica/fisiologia , Medo/efeitos dos fármacos , Medo/psicologia , Feminino , Agonistas de Receptores de GABA-A/farmacologia , Masculino , Memória/efeitos dos fármacos , Muscimol/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Reflexo de Sobressalto/efeitos dos fármacos
3.
Behav Neurol ; 2020: 9370891, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32148565

RESUMO

Objective: Propofol is a classical anesthetic and induces consciousness loss, and gamma-aminobutyric-acid-type-A (GABA-A) receptor is its target. Righting reflex is associated with conscious response. The nucleus basalis (NB) acts as a major relay between the reticular activating system and the frontal cortex (FC). Propofol may mediate righting reflex by affecting GABA-A receptor in NB. Methods: Fifty male SD rats (250-350 g) were divided into parts I and II. In part I, 20 male SD rats were randomly divided into control group (CG) and NB-lesion group (NG, ibotenic acid-induced NB lesion). In part II, 30 male SD rats were treated with saline (0.9% NaCl, SG group), muscimol (a GABA-A receptor agonist, MG group), and gabazine (a GABA-A receptor antagonist, GG group) in NB, respectively. Two weeks later, the activity of the rats was measured between CG and NG groups. The rats were intravenously injected with propofol (50 mg/kg/h) to test the time of loss of righting reflex (LORR) in all rats. When LORR occurred, the rats received single administration of propofol (12 mg/kg) to measure the time of return of righting reflex (RORR). Electroencephalogram (EEG) activity of the frontal cortex (FC) was recorded. Results: The numbers of NB neurons were reduced by 44% in the NG group compared to the CG group (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (p < 0.05) whereas the activity of rats was reduced a little in the NG group when compared with the CG group, but the statistical difference was insignificant (. Conclusions: The unilateral NB lesion increased the recovery time and FC delta power, and the NB region might be involved in the emergence after propofol administration. Propofol plays a crucial role for causing conscious loss by affecting GABA-A receptor in NB.


Assuntos
Núcleo Basal de Meynert/efeitos dos fármacos , Propofol/metabolismo , Receptores de GABA-A/efeitos dos fármacos , Animais , Núcleo Basal de Meynert/metabolismo , Estado de Consciência/efeitos dos fármacos , Estado de Consciência/fisiologia , Eletroencefalografia/métodos , Masculino , Muscimol/farmacologia , Propofol/farmacologia , Piridazinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de GABA-A/metabolismo
4.
Int J Mol Sci ; 21(6)2020 Mar 12.
Artigo em Inglês | MEDLINE | ID: mdl-32178439

RESUMO

While the descending dopaminergic control system is not fully understood, it is reported that the hypothalamic A11 nucleus is its principle source. To better understand the impact of this system, particularly the A11 nucleus, on neuropathic pain, we created a chronic constriction injury model of the infraorbital nerve (ION-CCI) in rats. ION-CCI rats received intraperitoneal administrations of quinpirole (a dopamine D2 receptor agonist). ION-CCI rats received microinjections of quinpirole, muscimol [a gamma-aminobutyric acid type A (GABAA) receptor agonist], or neurotoxin 6-hydroxydopamine (6-OHDA) into the A11 nucleus. A von Frey filament was used as a mechanical stimulus on the maxillary whisker pad skin; behavioral and immunohistochemical responses to the stimulation were assessed. After intraperitoneal administration of quinpirole and microinjection of quinpirole or muscimol, ION-CCI rats showed an increase in head-withdrawal thresholds and a decrease in the number of phosphorylated extracellular signal-regulated kinase (pERK) immunoreactive (pERK-IR) cells in the superficial layers of the trigeminal spinal subnucleus caudalis (Vc). Following 6-OHDA microinjection, ION-CCI rats showed a decrease in head-withdrawal thresholds and an increase in the number of pERK-IR cells in the Vc. Our findings suggest the descending dopaminergic control system is involved in the modulation of trigeminal neuropathic pain.


Assuntos
Nervos Cranianos/metabolismo , Dopamina/metabolismo , Traumatismos do Nervo Facial/metabolismo , Animais , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Agonistas de Receptores de GABA-A/farmacologia , Hiperalgesia/metabolismo , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Masculino , Muscimol/farmacologia , Neuralgia/metabolismo , Oxidopamina/farmacologia , Medição da Dor/métodos , Limiar da Dor/fisiologia , Fosforilação/efeitos dos fármacos , Quimpirol/farmacologia , Ratos , Ratos Wistar , Receptores de Dopamina D2/metabolismo , Medula Espinal/efeitos dos fármacos , Medula Espinal/metabolismo , Ácido gama-Aminobutírico/metabolismo
5.
J Neurosci ; 40(12): 2485-2497, 2020 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-32051327

RESUMO

We recently developed a rat model of relapse to drug seeking after food choice-induced voluntary abstinence. Here, we used this model to study the role of the orbitofrontal cortex (OFC) and its afferent projections in relapse to fentanyl seeking. We trained male and female rats to self-administer palatable food pellets for 6 d (6 h/d) and intravenous fentanyl (2.5 µg/kg/infusion) for 12 d (6 h/d). We assessed relapse to fentanyl seeking after 13-14 voluntary abstinence days, achieved through a discrete choice procedure between fentanyl infusions and palatable food (20 trials/d). In both sexes, relapse after food choice-induced abstinence was associated with increased expression of the activity marker Fos in the OFC. Pharmacological inactivation of the OFC with muscimol plus baclofen (50 + 50 ng/side) decreased relapse to fentanyl seeking. We then determined projection-specific activation of OFC afferents during the relapse test by using Fos plus the retrograde tracer cholera toxin B (injected into the OFC). Relapse to fentanyl seeking was associated with increased Fos expression in the piriform cortex (Pir) neurons projecting to the OFC, but not in projections from the basolateral amygdala and thalamus. Pharmacological inactivation of the Pir with muscimol plus baclofen decreased relapse to fentanyl seeking after voluntary abstinence. Next, we used an anatomical disconnection procedure to determine whether projections between the Pir and OFC are critical for relapse to fentanyl seeking. Unilateral muscimol plus baclofen injections into the Pir in one hemisphere plus unilateral muscimol plus baclofen injections into the OFC in the contralateral, but not ipsilateral, hemisphere decreased relapse. Our results identify Pir-OFC projections as a new motivation-related pathway critical to relapse to opioid seeking after voluntary abstinence.SIGNIFICANCE STATEMENT There are few preclinical studies of fentanyl relapse, and these studies have used experimenter-imposed extinction or forced abstinence procedures. In humans, however, abstinence is often voluntary, with drug available in the drug environment but forgone in favor of nondrug alternative reinforcers. We recently developed a rat model of drug relapse after palatable food choice-induced voluntary abstinence. Here, we used classical pharmacology, immunohistochemistry, and retrograde tracing to demonstrate a critical role of the piriform and orbitofrontal cortices in relapse to opioid seeking after voluntary abstinence.


Assuntos
Analgésicos Opioides , Comportamento de Procura de Droga , Fentanila , Transtornos Relacionados ao Uso de Opioides/fisiopatologia , Transtornos Relacionados ao Uso de Opioides/psicologia , Córtex Piriforme/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Animais , Baclofeno/administração & dosagem , Baclofeno/farmacologia , Comportamento de Escolha , Feminino , Preferências Alimentares , Agonistas GABAérgicos/administração & dosagem , Agonistas GABAérgicos/farmacologia , Expressão Gênica/efeitos dos fármacos , Genes fos , Masculino , Microinjeções , Muscimol/administração & dosagem , Muscimol/farmacologia , Ratos , Ratos Sprague-Dawley , Recidiva , Autoadministração
6.
J Neurosci ; 40(9): 1849-1861, 2020 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-31949108

RESUMO

Severe loss of excitatory synapses in key brain regions is thought to be one of the major mechanisms underlying stress-induced cognitive impairment. To date, however, the identity of the affected circuits remains elusive. Here we examined the effect of exposure to repeated multiple concurrent stressors (RMS) on the connectivity of the posterior parietal cortex (PPC) in adolescent male mice. We found that RMS led to layer-specific elimination of excitatory synapses with the most pronounced loss observed in deeper cortical layers. Quantitative analysis of cortical projections to the PPC revealed a significant loss of sensory and retrosplenial inputs to the PPC while contralateral and frontal projections were preserved. These results were confirmed by decreased synaptic strength from sensory, but not from contralateral, projections in stress-exposed animals. Functionally, RMS disrupted visuospatial working memory performance, implicating disrupted higher-order visual processing. These effects were not observed in mice subjected to restraint-only stress for an identical period of time. The PPC is considered to be a cortical hub for multisensory integration, working memory, and perceptual decision-making. Our data suggest that sensory information streams targeting the PPC may be impacted by recurring stress, likely contributing to stress-induced cognitive impairment.SIGNIFICANCE STATEMENT Repeated exposure to stress profoundly impairs cognitive functions like memory, attention, or decision-making. There is emerging evidence that stress not only impacts high-order regions of the brain, but may affect earlier stages of cognitive processing. Our work focuses on the posterior parietal cortex, a brain region supporting short-term memory, multisensory integration, and decision-making. We show evidence that repeated stress specifically damages sensory inputs to this region. This disruption of synaptic connectivity is linked to working memory impairment and is specific to repeated exposure to multiple stressors. Altogether, our data provide a potential alternative explanation to ailments previously attributed to downstream, cognitive brain structures.


Assuntos
Rede Nervosa/fisiopatologia , Lobo Parietal/fisiopatologia , Estresse Psicológico/fisiopatologia , Animais , Cognição , Fenômenos Eletrofisiológicos , Lateralidade Funcional , Agonistas GABAérgicos/farmacologia , Imuno-Histoquímica , Masculino , Memória de Curto Prazo , Camundongos , Camundongos Endogâmicos C57BL , Muscimol/farmacologia , Rede Nervosa/efeitos dos fármacos , Ruído , Optogenética , Lobo Parietal/efeitos dos fármacos , Restrição Física , Memória Espacial , Estresse Psicológico/psicologia , Sinapses , Percepção Visual
7.
Bull Exp Biol Med ; 168(3): 341-344, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31940131

RESUMO

Standard water-reinforced drug discrimination model was employed to train Wistar rats to discriminate the intraperitoneal injections of tricyclic antidepressant amitriptyline (5.4 mg/kg) and physiological saline. To examine the role of GABAA receptors in psychotropic action of amitriptyline, the substitution tests were performed with muscimol (0.1-1.0 mg/kg) and pregnenolone (30-50 mg/kg). Similar tests were carried out with amitriptyline interoceptive antagonists bicuculline (1 mg/kg), flumazenil (15 mg/kg), finasteride (5 mg/kg), and indomethacin (7.5 mg/kg). The study showed that interoceptive effects of amitriptyline depend on functional activity of GABAA receptors but not on the neurosteroid site of GABAA receptor complex.


Assuntos
Amitriptilina/farmacologia , Psicotrópicos/farmacologia , Receptores de GABA-A/metabolismo , Animais , Bicuculina/farmacologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/metabolismo , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Muscimol/farmacologia , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Pregnenolona/farmacologia , Ratos , Ratos Wistar
8.
Nat Commun ; 11(1): 136, 2020 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-31919353

RESUMO

Targeted manipulations of neural activity are essential approaches in neuroscience and neurology, but monitoring such procedures in the living brain remains a significant challenge. Here we introduce a paramagnetic analog of the drug muscimol that enables targeted neural inactivation to be performed with feedback from magnetic resonance imaging. We validate pharmacological properties of the compound in vitro, and show that its distribution in vivo reliably predicts perturbations to brain activity.


Assuntos
Ondas Encefálicas/fisiologia , Encéfalo/fisiologia , Imagem por Ressonância Magnética/métodos , Muscimol/farmacologia , Animais , Meios de Contraste/farmacologia , Agonistas GABAérgicos/química , Masculino , Muscimol/análogos & derivados , Ratos Sprague-Dawley , Ácido gama-Aminobutírico/química
9.
Neuron ; 105(2): 346-354.e5, 2020 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-31757603

RESUMO

Neocortical sensory areas are thought to act as distribution hubs, transmitting information about the external environment to downstream areas. Within primary visual cortex, various populations of pyramidal neurons (PNs) send axonal projections to distinct targets, suggesting multiple cellular networks may be independently engaged during behavior. We investigated whether PN subpopulations differentially support visual detection by training mice on a novel eyeblink conditioning task. Applying 2-photon calcium imaging and optogenetic manipulation of anatomically defined PNs, we show that layer 5 corticopontine neurons strongly encode sensory and motor task information and are selectively necessary for performance. Our findings support a model in which target-specific cortical subnetworks form the basis for adaptive behavior by directing relevant information to distinct brain areas. Overall, this work highlights the potential for neurons to form physically interspersed but functionally segregated networks capable of parallel, independent control of perception and behavior.


Assuntos
Córtex Cerebral/fisiologia , Condicionamento Palpebral/fisiologia , Corpo Estriado/fisiologia , Ponte/fisiologia , Córtex Visual/fisiologia , Vias Visuais/fisiologia , Animais , Nível de Alerta/fisiologia , Condicionamento Palpebral/efeitos dos fármacos , Camundongos , Muscimol/farmacologia , Técnicas de Rastreamento Neuroanatômico , Neurônios/fisiologia , Estimulação Luminosa
10.
New Phytol ; 225(2): 671-678, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31591723

RESUMO

Anion transport by aluminium-activated malate transporter (ALMT) proteins is negatively regulated by gamma-aminobutyric acid (GABA), which increases in concentration during stress. Here, the interaction between GABA and wheat (Triticum aestivum, Ta) TaALMT1 heterologously-expressed in Xenopus laevis oocytes was investigated. GABA inhibited anion transport by TaALMT1 in membrane patches from the cytosolic, not extracellular membrane face, via a reduction in open probability (NPopen ), not an inhibition of channel current magnitude. TaALMT1 currents in patches frequently exhibited rundown with complete removal of cytosolic factors, but were partially sustained by protein kinase C dependent phosphorylation. When applied to whole oocytes a GABA-analogue-BODIPY conjugate inhibited TaALMT1 anion currents from the cytoplasmic face only, whereas free GABA inhibited from both the inside and outside consistent with GABA traversing the TaALMT1 pore then acting from the inside. We propose GABA does not competitively inhibit ALMT conductance through the same pore but rather leads to an allosteric effect, reducing anion channel opening frequency. Across plants GABA is a conserved regulator of anion transport via ALMTs - a family with numerous physiological roles beyond Al3+ tolerance. Our data suggests that a GABA-ALMT interaction from the cytosolic face has the potential to form part of a novel plant signalling pathway.


Assuntos
Citosol/metabolismo , Proteínas de Plantas/metabolismo , Triticum/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Ânions , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Citosol/efeitos dos fármacos , Ativação do Canal Iônico/efeitos dos fármacos , Transporte de Íons/efeitos dos fármacos , Muscimol/farmacologia , Mutação/genética , Oócitos/efeitos dos fármacos , Oócitos/metabolismo , Xenopus laevis , Ácido gama-Aminobutírico/farmacologia
11.
J Vis Exp ; (153)2019 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-31789311

RESUMO

This microinjectrode system is designed for drug infusion, electrophysiology, and delivery and retrieval of experimental probes, such as microelectrodes and nanosensors, optimized for repeated use in awake, behaving animals. The microinjectrode system can be configured for multiple purposes: (1) simple arrangement of the cannula for placement of an experimental probe that would otherwise be too fragile to penetrate the dura mater, (2) microfluidic infusion of a drug, either independently or coupled to a cannula containing an experimental probe (i.e., microelectrode, nanosensor). In this protocol we explain the step by step construction of the microinjectrode, its coupling to microfluidic components, and the protocol for use of the system in vivo. The microfluidic components of this system allow for delivery of volumes on the nanoliter scale, with minimal penetration damage. Drug infusion can be performed independently or simultaneously with experimental probes such as microelectrodes or nanosensors in an awake, behaving animal. Applications of this system range from measuring the effects of a drug on cortical electrical activity and behavior, to understanding the function of a specific region of cortex in the context of behavioral performance based on probe or nanosensor measurements. To demonstrate some of the capabilities of this system, we present an example of muscimol infusion for reversible inactivation of the frontal eye field (FEF) in rhesus macaque during a working memory task.


Assuntos
Fenômenos Eletrofisiológicos , Preparações Farmacêuticas/administração & dosagem , Animais , Macaca mulatta , Memória , Microeletrodos , Microfluídica , Muscimol/administração & dosagem , Muscimol/farmacologia , Movimentos Sacádicos/efeitos dos fármacos , Movimentos Sacádicos/fisiologia , Análise e Desempenho de Tarefas , Campos Visuais/efeitos dos fármacos , Vigília/efeitos dos fármacos
12.
PLoS Biol ; 17(12): e3000524, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31805039

RESUMO

Social transmission of freezing behavior has been conceived of as a one-way phenomenon in which an observer "catches" the fear of another. Here, we use a paradigm in which an observer rat witnesses another rat receiving electroshocks. Bayesian model comparison and Granger causality show that rats exchange information about danger in both directions: how the observer reacts to the demonstrator's distress also influences how the demonstrator responds to the danger. This was true to a similar extent across highly familiar and entirely unfamiliar rats but is stronger in animals preexposed to shocks. Injecting muscimol in the anterior cingulate of observers reduced freezing in the observers and in the demonstrators receiving the shocks. Using simulations, we support the notion that the coupling of freezing across rats could be selected for to more efficiently detect dangers in a group, in a way similar to cross-species eavesdropping.


Assuntos
Medo/fisiologia , Medo/psicologia , Reação de Congelamento Cataléptica/fisiologia , Comunicação Animal , Animais , Teorema de Bayes , Comportamento Animal/fisiologia , Giro do Cíngulo/efeitos dos fármacos , Giro do Cíngulo/fisiologia , Masculino , Muscimol/farmacologia , Ratos , Ratos Long-Evans , Ratos Sprague-Dawley , Comportamento Social
13.
Nat Neurosci ; 22(11): 1771-1781, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31636449

RESUMO

Microglia dynamically survey the brain parenchyma. Microglial processes interact with neuronal elements; however, what role neuronal network activity plays in regulating microglial dynamics is not entirely clear. Most studies of microglial dynamics use either slice preparations or in vivo imaging in anesthetized mice. Here we demonstrate that microglia in awake mice have a relatively reduced process area and surveillance territory and that reduced neuronal activity under general anesthesia increases microglial process velocity, extension and territory surveillance. Similarly, reductions in local neuronal activity through sensory deprivation or optogenetic inhibition increase microglial process surveillance. Using pharmacological and chemogenetic approaches, we demonstrate that reduced norepinephrine signaling is necessary for these increases in microglial process surveillance. These findings indicate that under basal physiological conditions, noradrenergic tone in awake mice suppresses microglial process surveillance. Our results emphasize the importance of awake imaging for studying microglia-neuron interactions and demonstrate how neuronal activity influences microglial process dynamics.


Assuntos
Microglia/fisiologia , Neurônios/fisiologia , Norepinefrina/fisiologia , Córtex Somatossensorial/fisiologia , Animais , Encéfalo/efeitos dos fármacos , Receptor 1 de Quimiocina CX3C/genética , Clozapina/análogos & derivados , Clozapina/farmacologia , Isoflurano/farmacologia , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Microglia/efeitos dos fármacos , Microinjeções , Muscimol/farmacologia , Norepinefrina/farmacologia , Optogenética , Propanolaminas/farmacologia , Propranolol/farmacologia , Receptores Purinérgicos P2Y12/genética , Privação Sensorial/fisiologia , Córtex Somatossensorial/efeitos dos fármacos , Tetrodotoxina/farmacologia , Vigília
14.
Neuropsychopharmacol Rep ; 39(4): 289-296, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31618533

RESUMO

AIM: The lateral hypothalamus (LH) is known as the hunger center, but the mechanisms through which the LH regulates food intake are unclear. Since GABA neurons are reported to project to the LH, the present study investigated the role of GABAergic function in the LH in the regulation of feeding behavior. METHODS: GABA levels in the LH were measured by in vivo microdialysis. Food intake after drug injection into the LH was measured every 1 hour for 4 hours. The mRNA levels were measured using RT-PCR. RESULTS: Food intake significantly increased GABA levels in the LH, suggesting that food intake stimulates GABAergic function in the LH. Injection of the GABAA receptor agonist muscimol into the LH significantly inhibited food intake, whereas injection of the GABAA receptor antagonist bicuculline into the LH did not significantly affect food intake. The inhibitory effect of muscimol injected into the LH was blocked by co-administration of bicuculline. These results indicate that the stimulation of GABAA receptors in the LH inhibits food intake. We next examined whether the stimulation of GABAA receptors affects hypothalamic neuropeptides that are known to regulate feeding behavior. The injection of muscimol significantly decreased preproorexin mRNA in the hypothalamus. CONCLUSION: These results indicate that food intake activates GABAergic function in the LH, which terminates feeding behavior by stimulating GABAA receptors. Moreover, it is suggested that the stimulation of GABAA receptors in the LH reduces food intake through inhibition of orexin neurons.


Assuntos
Ingestão de Alimentos/fisiologia , Região Hipotalâmica Lateral/metabolismo , Orexinas/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Bicuculina/farmacologia , Ingestão de Alimentos/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Comportamento Alimentar/fisiologia , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Região Hipotalâmica Lateral/efeitos dos fármacos , Microdiálise , Muscimol/farmacologia
15.
Eur J Neurosci ; 50(10): 3599-3613, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31410900

RESUMO

Non-invasive reversible perturbation techniques of brain output such as continuous theta burst stimulation (cTBS), commonly used to modulate cortical excitability in humans, allow investigation of possible roles in functional recovery played by distinct intact cortical areas following stroke. To evaluate the potential of cTBS, the behavioural effects of this non-invasive transient perturbation of the hand representation of the primary motor cortex (M1) in non-human primates (two adult macaques) were compared with an invasive focal transient inactivation based on intracortical microinfusion of GABA-A agonist muscimol. The effects on the contralateral arm produced by cTBS or muscimol were directly compared based on a manual dexterity task performed by the monkeys, the "reach and grasp" drawer task, allowing quantitative assessment of the grip force produced between the thumb and index finger and exerted on the drawer's knob. cTBS only induced modest to moderate behavioural effects, with substantial variability on manual dexterity whereas the intracortical muscimol microinfusion completely impaired manual dexterity, producing a strong and clear cortical inhibition of the M1 hand area. In contrast, cTBS induced mixed inhibitory and facilitatory/excitatory perturbations of M1, though with predominant inhibition. Although cTBS impacted on manual dexterity, its effects appear too limited and variable in order to use it as a reliable proof of cortical vicariation mechanism (cortical area replacing another one) underlying functional recovery following a cortical lesion in the motor control domain, in contrast to potent pharmacological block generated by muscimol infusion, whose application is though limited to an animal model such as non-human primate.


Assuntos
Estimulação Encefálica Profunda/métodos , Mãos/fisiologia , Córtex Motor/fisiologia , Destreza Motora , Ritmo Teta , Animais , Estimulação Encefálica Profunda/efeitos adversos , Feminino , Agonistas de Receptores de GABA-A/farmacologia , Macaca fascicularis , Masculino , Córtex Motor/efeitos dos fármacos , Muscimol/farmacologia
16.
Behav Brain Res ; 374: 112114, 2019 11 18.
Artigo em Inglês | MEDLINE | ID: mdl-31351844

RESUMO

Learning and remembering the context in which events occur requires interactions between the hippocampus (HPC) and medial prefrontal cortex (mPFC). The nucleus reuniens (RE) is a ventral midline thalamic nucleus that coordinates activity in the mPFC and HPC and is involved in spatial and contextual memory. We recently found that the RE is critical for contextual fear conditioning in rats, a form of learning that involves interactions between the HPC and mPFC. Here we examined whether the RE mediates the extinction of contextual fear. After contextual fear conditioning, rats underwent an extinction procedure in which they were merely exposed to the conditioning context; freezing behavior during the extinction procedure and during a retrieval test 24 h later served as an index of conditioned fear. Muscimol inactivation of the RE prior to extinction impaired the acquisition of both short- and long-term extinction memories. Similarly, inactivation of the RE prior to the extinction retrieval test also impaired the expression of extinction; this effect was not state-dependent. Taken together, these results reveal that the extinction of contextual fear memories requires the RE, which is consistent with a broader role for the RE in forms of learning that require HPC-mPFC interactions.


Assuntos
Extinção Psicológica/fisiologia , Medo/fisiologia , Núcleos da Linha Média do Tálamo/fisiologia , Animais , Encéfalo/fisiologia , Condicionamento Clássico/fisiologia , Medo/psicologia , Hipocampo/fisiologia , Aprendizagem/fisiologia , Masculino , Memória/fisiologia , Memória de Longo Prazo/fisiologia , Rememoração Mental/fisiologia , Núcleos da Linha Média do Tálamo/metabolismo , Muscimol/farmacologia , Vias Neurais/fisiologia , Córtex Pré-Frontal/fisiologia , Ratos , Ratos Long-Evans
17.
Food Chem Toxicol ; 132: 110687, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31325463

RESUMO

Muscimol is the main compound found in Amanita muscaria. Several studies have proven that muscimol has suppressive effects on essential tremor, without impairing speech and coordination. The effects of muscimol in Parkinson-affected patients is also described in a number of studies. These studies describe the free radical scavenging and antioxidant activity of the mushroom extract. We have evaluated the possible neuroprotective effects of a standardized extract from A. muscaria, containing high amounts of muscimol, on different models of neurotoxicity in rat brain microsomes, mitochondria, synaptosomes as well as on neuroblastoma cell line SH-SY5Y. The possible inhibitory effect on human recombinant monoaminoxidase-B (hMAOB) enzyme was also studied. The extract revealed statistically significant neuroprotective effects on the in vitro neurotoxicity models and no inhibitory activity on hMAOB.


Assuntos
Amanita/química , Muscimol/farmacologia , Animais , Antioxidantes/farmacologia , Encéfalo/efeitos dos fármacos , Linhagem Celular Tumoral , Humanos , Masculino , Monoaminoxidase/efeitos dos fármacos , Muscimol/isolamento & purificação , Fármacos Neuroprotetores/farmacologia , Organelas/efeitos dos fármacos , Ratos , Ratos Wistar
18.
Cell Rep ; 28(3): 616-624.e5, 2019 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-31315042

RESUMO

Overeating is a serious issue in modern society, causing many health problems, including obesity. Although the hypothalamus has been previously identified as the key brain structure that regulates body weight homeostasis, the downstream pathways and non-canonical neural circuitry involved in feeding behavior remain largely uncharacterized. Here, we discover that suppressing the activity of GABAergic cells in the anterior ventrolateral periaqueductal gray (vlPAG), whether directly or through long-projection GABAergic inputs from either the bed nucleus of the stria terminalis (BNST) or the lateral hypothalamus (LH), is sufficient to promptly induce feeding behavior in well-fed mice. In contrast, optogenetic activation of these cells interrupts food intake in starved mice. Long-term chemogenetic manipulation of vlPAG GABAergic cell activity elicits a corresponding change in mouse body weight. Our studies reveal distinct midbrain GABAergic pathways and highlight an important role of GABAergic cells in the anterior vlPAG in feeding behavior.


Assuntos
Comportamento Alimentar/psicologia , Neurônios GABAérgicos/fisiologia , Região Hipotalâmica Lateral/fisiologia , Vias Neurais/fisiologia , Substância Cinzenta Periaquedutal/fisiologia , Núcleos Septais/fisiologia , Animais , Antipsicóticos/farmacologia , Peso Corporal/efeitos dos fármacos , Peso Corporal/genética , Peso Corporal/fisiologia , Núcleo Central da Amígdala/efeitos dos fármacos , Núcleo Central da Amígdala/fisiologia , Clozapina/análogos & derivados , Clozapina/farmacologia , Comportamento Alimentar/fisiologia , Agonistas de Receptores de GABA-A/farmacologia , Neurônios GABAérgicos/citologia , Neurônios GABAérgicos/efeitos dos fármacos , Neurônios GABAérgicos/metabolismo , Região Hipotalâmica Lateral/citologia , Camundongos , Muscimol/farmacologia , Optogenética , Substância Cinzenta Periaquedutal/citologia , Substância Cinzenta Periaquedutal/efeitos dos fármacos , Substância Cinzenta Periaquedutal/efeitos da radiação , Núcleos Septais/citologia
19.
Pharmacol Rep ; 71(4): 636-643, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31176893

RESUMO

BACKGROUND: The inverse relationship between GnRH transcript level and GABA neurons activity has suggested that GABA at the hypothalamic level may exert a suppressive effect on subsequent steps of the GnRH biosynthesis. In the present study, we analyzed the effects of GABA type A receptor agonist (muscimol) or antagonist (bicuculline) on molecular mechanisms governing GnRH/LH secretion in follicular-phase sheep. METHODS: ELISA technique was used to investigate the effects of muscimol and/or bicuculline on levels of post-translational products of genes encoding GnRH ligand and GnRH receptor (GnRHR) in the preoptic area (POA), anterior (AH) and ventromedial (VMH) hypothalamus, stalk/median eminence (SME), and GnRHR in the anterior pituitary (AP). Real-time PCR was chosen for determination of the effect of drugs on kisspeptin (Kiss 1) mRNA level in POA and VMH including arcuate nucleus (VMH/ARC), and on Kiss1 receptor (Kiss1r) mRNA abundance in POA-hypothalamic structures. These analyses were supplemented by RIA method for measurement of plasma LH concentration. RESULTS: The study demonstrated that muscimol and bicuculline significantly decreased or increased GnRH biosynthesis in all analyzed structures, respectively, and led to analogous changes in plasma LH concentration. Similar muscimol- and bicuculline-related alterations were observed in levels of GnRHR. However, the expression of Kiss 1 and Kiss1r mRNAs in selected POA-hypothalamic areas of either muscimol- and bicuculline-treated animals remained unaltered. CONCLUSIONS: Our data suggest that GABAergic neurotransmission is involved in the regulatory pathways of GnRH/GnRHR biosynthesis and then GnRH/LH release in follicular-phase sheep conceivably via indirect mechanisms that exclude involvement of Kiss 1 neurons.


Assuntos
Ciclo Estral/metabolismo , Hormônio Liberador de Gonadotropina/biossíntese , Sistema Hipotálamo-Hipofisário/efeitos dos fármacos , Kisspeptinas/metabolismo , Receptores de GABA-A/metabolismo , Receptores LHRH/biossíntese , Animais , Bicuculina/farmacologia , Feminino , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Hormônio Liberador de Gonadotropina/sangue , Sistema Hipotálamo-Hipofisário/metabolismo , Muscimol/farmacologia , Neurônios/metabolismo , Ovinos
20.
Restor Neurol Neurosci ; 37(4): 315-331, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31227671

RESUMO

BACKGROUND: GABAA receptors modulate the behavioral recovery encountered in both experimental animals and patients with ischemic injury, possibly through promoting structural plasticity. We hypothesized that activation of GABAA receptors would regulate axonal growth, which in turn would improve the behavioral recovery in ischemic rats. OBJECTIVE: To investigate the effects of muscimol on axonal growth, synaptic plasticity and behavioral performance in rats after a focal ischemia induced by endothelin-1 (ET-1). METHODS: Focal ischemic infarct was induced by ET-1. The rats were randomly divided into 3 groups: sham-operated group, ischemic group, ischemic+muscimol group. The muscimol infusion into contralateral cortex started on post-operative day 7 continuing until day 21. Biotinylated dextran amine was injected on post-operative day 14 into the contralesional motor cortex to trace the crossing corticospinal tract fibers. The expression levels of growth inhibitors, Nogo receptor, NogoA, RhoA, and Rho-associated kinase were measured in the peri-infarct cortex. The expressions of vGlut-1 and postsynaptic density-95 were measured by immunohistochemistry and Western blot in the denervated spinal cord. The behavioral recovery was evaluated by sensorimotor tests on post-operative days 32-34. RESULTS: Treatment with the specific GABAA receptors agonist, muscimol, did not increase axonal growth into the denervated hemispheres and spinal cord after stroke. However, the activation of GABAA receptors partially improved the rats' behavioral performance after the ET-1-induced stroke. CONCLUSIONS: Our study revealed that infusion of muscimol into the contralateral motor cortex during the repair stage could partially improve the behavioral performances without promoting axonal growth from uninjured hemisphere motor cortex to the denervated striatum and spinal cord, nor did it prevent the expression of axonal growth inhibitors in peri-lesioned cortex. More detailed studies will be required to clarify the role of GABAA Rs in regulating the behavioral recovery after a stroke.


Assuntos
Axônios/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacos , Infarto Encefálico/tratamento farmacológico , Agonistas de Receptores de GABA-A/farmacologia , Córtex Motor/efeitos dos fármacos , Muscimol/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Receptores de GABA-A/fisiologia , Recuperação de Função Fisiológica/efeitos dos fármacos , Animais , Modelos Animais de Doenças , Agonistas de Receptores de GABA-A/administração & dosagem , Muscimol/administração & dosagem , Ratos
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