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1.
Pain ; 164(5): 1051-1066, 2023 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-36448978

RESUMO

ABSTRACT: The nucleus of the solitary tract (NTS) contains pro-opiomelanocortin (POMC) neurons that are 1 of the 2 major sources of ß-endorphin in the brain. The functional role of these NTS POMC neurons in nociceptive and cardiorespiratory function is debated. We have shown that NTS POMC optogenetic activation produces bradycardia and transient apnoea in a working heart-brainstem preparation and chemogenetic activation with an engineered ion channel (PSAM) produced opioidergic analgesia in vivo. To better define the role of the NTS POMC neurons in behaving animals, we adopted in vivo optogenetics (ChrimsonR) and excitatory/inhibitory chemogenetic DREADD (hM3Dq/hM4Di) strategies in POMC-Cre mice. We show that optogenetic activation of NTS POMC neurons produces time-locked, graded, transient bradycardia and bradypnoea in anaesthetised mice that is naloxone sensitive (1 mg/kg, i.p.), suggesting a role of ß-endorphin. Both optogenetic and chemogenetic activation of NTS POMC neurons produces sustained thermal analgesia in behaving mice that can be blocked by naloxone. It also produced analgesia in an inflammatory pain model (carrageenan) but not in a neuropathic pain model (tibial nerve transection). Inhibiting NTS POMC neurons does not produce any effect on basal nociception but inhibits stress-induced analgesia (unlike inhibition of arcuate POMC neurons). Activation of NTS POMC neuronal populations in conscious mice did not cause respiratory depression, anxiety, or locomotor deficit (in open field) or affective preference. These findings indicate that NTS POMC neurons play a key role in the generation of endorphinergic endogenous analgesia and can also regulate cardiorespiratory function.


Assuntos
Analgesia , Pró-Opiomelanocortina , Camundongos , Animais , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , Pró-Opiomelanocortina/farmacologia , Núcleo Solitário , Bradicardia , beta-Endorfina , Neurônios , Naloxona/farmacologia , Dor
2.
Nat Commun ; 13(1): 4150, 2022 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-35851064

RESUMO

The development of therapeutic agonists for G protein-coupled receptors (GPCRs) is hampered by the propensity of GPCRs to couple to multiple intracellular signalling pathways. This promiscuous coupling leads to numerous downstream cellular effects, some of which are therapeutically undesirable. This is especially the case for adenosine A1 receptors (A1Rs) whose clinical potential is undermined by the sedation and cardiorespiratory depression caused by conventional agonists. We have discovered that the A1R-selective agonist, benzyloxy-cyclopentyladenosine (BnOCPA), is a potent and powerful analgesic but does not cause sedation, bradycardia, hypotension or respiratory depression. This unprecedented discrimination between native A1Rs arises from BnOCPA's unique and exquisitely selective activation of Gob among the six Gαi/o subtypes, and in the absence of ß-arrestin recruitment. BnOCPA thus demonstrates a highly-specific Gα-selective activation of the native A1R, sheds new light on GPCR signalling, and reveals new possibilities for the development of novel therapeutics based on the far-reaching concept of selective Gα agonism.


Assuntos
Analgesia , Depressão , Adenosina/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Receptores Purinérgicos P1
3.
Elife ; 112022 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-35018884

RESUMO

Agouti-related peptide (AgRP) neurons increase motivation for food, however, whether metabolic sensing of homeostatic state in AgRP neurons potentiates motivation by interacting with dopamine reward systems is unexplored. As a model of impaired metabolic-sensing, we used the AgRP-specific deletion of carnitine acetyltransferase (Crat) in mice. We hypothesised that metabolic sensing in AgRP neurons is required to increase motivation for food reward by modulating accumbal or striatal dopamine release. Studies confirmed that Crat deletion in AgRP neurons (KO) impaired ex vivo glucose-sensing, as well as in vivo responses to peripheral glucose injection or repeated palatable food presentation and consumption. Impaired metabolic-sensing in AgPP neurons reduced acute dopamine release (seconds) to palatable food consumption and during operant responding, as assessed by GRAB-DA photometry in the nucleus accumbens, but not the dorsal striatum. Impaired metabolic-sensing in AgRP neurons suppressed radiolabelled 18F-fDOPA accumulation after ~30 min in the dorsal striatum but not the nucleus accumbens. Impaired metabolic sensing in AgRP neurons suppressed motivated operant responding for sucrose rewards during fasting. Thus, metabolic-sensing in AgRP neurons is required for the appropriate temporal integration and transmission of homeostatic hunger-sensing to dopamine signalling in the striatum.


Assuntos
Proteína Relacionada com Agouti/genética , Corpo Estriado/fisiologia , Dopamina/fisiologia , Homeostase , Neurônios/fisiologia , Transdução de Sinais , Proteína Relacionada com Agouti/metabolismo , Animais , Camundongos , Camundongos Knockout
4.
Neuropharmacology ; 198: 108755, 2021 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-34416268

RESUMO

Excitatory and inhibitory neurotransmission within the spinal dorsal horn is tightly controlled to regulate transmission of nociceptive signals to the brain. One aspect of this control is modulation of neuronal activity through cholinergic signaling. Nociceptive neurons in the dorsal horn express both nicotinic and muscarinic cholinergic receptors and activation of these receptors reduces pain in humans, while inhibition leads to nociceptive hypersensitivity. At a cellular level, acetylcholine (ACh) has diverse effects on excitability which is dependent on the receptor and neuronal subtypes involved. In the present study we sought to characterize the electrophysiological responses of specific subsets of lamina II interneurons from rat and marmoset spinal cord. Neurons were grouped by morphology and by action potential firing properties. Whole-cell voltage-clamp recordings from lamina II dorsal horn neurons of adult rats showed that bath applied acetylcholine increased, decreased or had no effect on spontaneous synaptic current activity in a cell-type specific manner. ACh modulated inhibitory synaptic activity in 80% of neurons, whereas excitatory synaptic activity was affected in less than 50% of neurons. In whole-cell current clamp recordings, brief somatic application of ACh induced cell-type specific responses in 79% of rat lamina II neurons, which included: depolarization and action potential firing, subthreshold membrane depolarization, biphasic responses characterized by transient depolarization followed by hyperpolarization and membrane hyperpolarization alone. Similar responses were seen in marmoset lamina II neurons and the properties of each neuron group were consistent across species. ACh-induced hyperpolarization was blocked by the muscarinic antagonist atropine and all forms of acetylcholine-induced depolarization were blocked by the nicotinic antagonist mecamylamine. The cholinergic system plays an important role in regulating nociception and this study contributes to our understanding of how circuit activity is controlled by ACh at a cellular level in primate and rodent spinal cord.


Assuntos
Acetilcolina/farmacologia , Rede Nervosa/efeitos dos fármacos , Células do Corno Posterior/efeitos dos fármacos , Potenciais de Ação/efeitos dos fármacos , Animais , Atropina/farmacologia , Callithrix , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Interneurônios/efeitos dos fármacos , Masculino , Mecamilamina/farmacologia , Camundongos , Antagonistas Muscarínicos/farmacologia , Antagonistas Nicotínicos/farmacologia , Nociceptividade/efeitos dos fármacos , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley
5.
J Med Chem ; 64(6): 3222-3233, 2021 03 25.
Artigo em Inglês | MEDLINE | ID: mdl-33724033

RESUMO

Several Conus-derived venom peptides are promising lead compounds for the management of neuropathic pain, with α-conotoxins being of particular interest. Modification of the interlocked disulfide framework of α-conotoxin Vc1.1 has been achieved using on-resin alkyne metathesis. Although introduction of a metabolically stable alkyne motif significantly disrupts backbone topography, the structural modification generates a potent and selective GABAB receptor agonist that inhibits Cav2.2 channels and exhibits dose-dependent reversal of mechanical allodynia in a behavioral rat model of neuropathic pain. The findings herein support the hypothesis that analgesia can be achieved via activation of GABABRs expressed in dorsal root ganglion (DRG) sensory neurons.


Assuntos
Alcinos/uso terapêutico , Analgésicos/uso terapêutico , Conotoxinas/uso terapêutico , Hiperalgesia/tratamento farmacológico , Neuralgia/tratamento farmacológico , Alcinos/química , Analgésicos/química , Animais , Células Cultivadas , Conotoxinas/química , Caramujo Conus/química , Modelos Animais de Doenças , Feminino , Células HEK293 , Humanos , Hiperalgesia/fisiopatologia , Masculino , Modelos Moleculares , Neuralgia/fisiopatologia , Ratos Sprague-Dawley , Xenopus
6.
Biol Psychiatry ; 90(12): 819-828, 2021 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-32892984

RESUMO

BACKGROUND: The ability to adapt behavior to changing environmental circumstances, or cognitive flexibility, is impaired in multiple psychiatric conditions, including anorexia nervosa (AN). Exaggerated prefrontal cortical activity likely underpins the inflexible thinking and rigid behaviors exhibited by patients with AN. A better understanding of the neural basis of cognitive flexibility is necessary to enable treatment approaches that may target impaired executive control. METHODS: Utilizing the activity-based anorexia (ABA) model and touchscreen operant learning paradigms, we investigated the neurobiological link between pathological weight loss and cognitive flexibility. We used pathway-specific chemogenetics to selectively modulate activity in neurons of the medial prefrontal cortex (mPFC) projecting to the nucleus accumbens shell (AcbSh) in female Sprague Dawley rats. RESULTS: DREADD (designer receptor exclusively activated by designer drugs)-based inhibition of the mPFC-AcbSh pathway prevented weight loss in ABA and improved flexibility during early reversal learning by reducing perseverative responding. Modulation of activity within the mPFC-AcbSh pathway had no effect on running, locomotor activity, or feeding under ad libitum conditions, indicating the specific involvement of this circuit in conditions of dysregulated reward. CONCLUSIONS: Parallel attenuation of weight loss in ABA and improvement of cognitive flexibility following suppression of mPFC-AcbSh activity align with the relationship between disrupted prefrontal function and cognitive rigidity in AN patients. The identification of a neurobiological correlate between cognitive flexibility and pathological weight loss provides a unique insight into the executive control of feeding behavior. It also highlights the utility of the ABA model for understanding the biological bases of cognitive deficits in AN and provides context for new treatment strategies.


Assuntos
Anorexia , Córtex Pré-Frontal , Animais , Cognição , Feminino , Humanos , Ratos , Ratos Sprague-Dawley , Redução de Peso
7.
Toxins (Basel) ; 12(8)2020 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-32781580

RESUMO

Several analgesic α-conotoxins have been isolated from marine cone snails. Structural modification of native peptides has provided potent and selective analogues for two of its known biological targets-nicotinic acetylcholine and γ-aminobutyric acid (GABA) G protein-coupled (GABAB) receptors. Both of these molecular targets are implicated in pain pathways. Despite their small size, an incomplete understanding of the structure-activity relationship of α-conotoxins at each of these targets has hampered the development of therapeutic leads. This review scrutinises the N-terminal domain of the α-conotoxin family of peptides, a region defined by an invariant disulfide bridge, a turn-inducing proline residue and multiple polar sidechain residues, and focusses on structural features that provide analgesia through inhibition of high-voltage-activated Ca2+ channels. Elucidating the bioactive conformation of this region of these peptides may hold the key to discovering potent drugs for the unmet management of debilitating chronic pain associated with a wide range of medical conditions.


Assuntos
Analgésicos/química , Conotoxinas/química , Peptídeos/química , Peptidomiméticos/química , Analgesia , Analgésicos/uso terapêutico , Animais , Dissulfetos/química , Humanos , Peptídeos/uso terapêutico , Peptidomiméticos/uso terapêutico , Conformação Proteica
8.
Mol Metab ; 34: 54-71, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32180560

RESUMO

OBJECTIVES: Nutrient sensing by hypothalamic neurons is critical for the regulation of food intake and energy expenditure. We aimed to identify long- and medium-chain fatty acid species transported into the brain, their effects on energy balance, and the mechanisms by which they regulate activity of hypothalamic neurons. METHODS: Simultaneous blood and cerebrospinal fluid (CSF) sampling was undertaken in rats and metabolic analyses using radiolabeled fatty acid tracers were performed on mice. Electrophysiological recording techniques were used to investigate signaling mechanisms underlying fatty acid-induced changes in activity of pro-opiomelanocortin (POMC) neurons. RESULTS: Medium-chain fatty acid (MCFA) octanoic acid (C8:0), unlike long-chain fatty acids, was rapidly transported into the hypothalamus of mice and almost exclusively oxidized, causing rapid, transient reductions in food intake and increased energy expenditure. Octanoic acid differentially regulates the excitability of POMC neurons, activating these neurons directly via GPR40 and inducing inhibition via an indirect non-synaptic, purine, and adenosine receptor-dependent mechanism. CONCLUSIONS: MCFA octanoic acid is a central signaling nutrient that targets POMC neurons via distinct direct and indirect signal transduction pathways to instigate changes in energy status. These results could explain the beneficial health effects that accompany MCFA consumption.


Assuntos
Caprilatos/metabolismo , Metabolismo Energético , Neurônios/metabolismo , Animais , Masculino , Ratos , Ratos Wistar
9.
J Neuroendocrinol ; 31(7): e12696, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30742723

RESUMO

Information about metabolic status arrives in the brain in the form of a complex milieu of circulating signalling factors, including glucose and fatty acids, ghrelin, leptin and insulin. The specific interactions between humoural factors, brain sites of action and how they influence behaviour are largely unknown. We have previously observed interactions between glucose availability and the actions of ghrelin mediated via the agouti-related peptide neurones of the hypothalamus. In the present study, we examine whether these effects generalise to another ghrelin-sensitive brain nucleus, the ventral tegmental area (VTA). We altered glucose availability by injecting mice with glucose or 2-deoxyglucose i.p. to induce hyperglycaemia and glucopenia, respectively. Thirty minutes later, we injected ghrelin in the VTA. Glucose administration suppressed intra-VTA ghrelin-induced feeding. Leptin, a longer-term signal of positive energy balance, did not affect intra-VTA ghrelin-induced feeding. 2-Deoxyglucose and ghrelin both increased food intake in their own right and, together, they additively increased feeding. These results add support to the idea that calculation of metabolic need depends on multiple signals across multiple brain regions and identifies that VTA circuits are sensitive to the integration of signals reflecting internal homeostatic state and influencing food intake.


Assuntos
Ingestão de Alimentos/fisiologia , Grelina/fisiologia , Glucose/administração & dosagem , Área Tegmentar Ventral/fisiologia , Animais , Glicemia/efeitos dos fármacos , Desoxiglucose/administração & dosagem , Ingestão de Alimentos/efeitos dos fármacos , Grelina/administração & dosagem , Camundongos Endogâmicos C57BL , Área Tegmentar Ventral/efeitos dos fármacos
10.
Elife ; 72018 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-30230471

RESUMO

Hypothalamic neurons respond to nutritional cues by altering gene expression and neuronal excitability. The mechanisms that control such adaptive processes remain unclear. Here we define populations of POMC neurons in mice that are activated or inhibited by insulin and thereby repress or inhibit hepatic glucose production (HGP). The proportion of POMC neurons activated by insulin was dependent on the regulation of insulin receptor signaling by the phosphatase TCPTP, which is increased by fasting, degraded after feeding and elevated in diet-induced obesity. TCPTP-deficiency enhanced insulin signaling and the proportion of POMC neurons activated by insulin to repress HGP. Elevated TCPTP in POMC neurons in obesity and/or after fasting repressed insulin signaling, the activation of POMC neurons by insulin and the insulin-induced and POMC-mediated repression of HGP. Our findings define a molecular mechanism for integrating POMC neural responses with feeding to control glucose metabolism.


Assuntos
Glucose/metabolismo , Insulina/farmacologia , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/metabolismo , Pró-Opiomelanocortina/metabolismo , Animais , Humanos , Hipoglicemiantes/administração & dosagem , Hipoglicemiantes/farmacologia , Hipotálamo/citologia , Insulina/administração & dosagem , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Plasticidade Neuronal/genética , Pró-Opiomelanocortina/genética , Proteína Tirosina Fosfatase não Receptora Tipo 2/genética , Proteína Tirosina Fosfatase não Receptora Tipo 2/metabolismo , Receptor de Insulina/genética , Receptor de Insulina/metabolismo
11.
Endocrinology ; 159(11): 3605-3614, 2018 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-30204871

RESUMO

Metabolic feedback from the periphery to the brain results from a dynamic physiologic fluctuation of nutrients and hormones, including glucose and fatty acids, ghrelin, leptin, and insulin. The specific interactions between humoral factors and how they influence feeding is largely unknown. We hypothesized that acute glucose availability may alter how the brain responds to ghrelin, a hormonal signal of energy availability. Acute glucose administration suppressed a range of ghrelin-induced behaviors as well as gene expression changes in hypothalamic neuropeptide Y (NPY) and agouti-related peptide (AgRP) neurons after ghrelin administration. Knockdown of the energy-sensing molecule AMP-activated protein kinase (AMPK) in AgRP neurons resulted in loss of the glucose effect, and mice responded as though pretreated with saline. Conversely, 2-deoxyglucose (2-DG), which decreases glucose availability, potentiated ghrelin-induced feeding and increased hypothalamic NPY mRNA levels. AMPK knockdown did not alter the additive effect of 2-DG and ghrelin on feeding. Our findings support the idea that computation of energy status is dynamic, is informed by multiple signals, and responds to acute fluctuations in metabolic state. These observations are broadly relevant to the investigation of neuroendocrine control of feeding and highlight the underappreciated complexity of control within these systems.


Assuntos
Proteína Relacionada com Agouti/efeitos dos fármacos , Núcleo Arqueado do Hipotálamo/efeitos dos fármacos , Comportamento Alimentar/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Grelina/farmacologia , Glucose/farmacologia , Neurônios/efeitos dos fármacos , Neuropeptídeo Y/efeitos dos fármacos , RNA Mensageiro/efeitos dos fármacos , Proteínas Quinases Ativadas por AMP/efeitos dos fármacos , Proteínas Quinases Ativadas por AMP/metabolismo , Proteína Relacionada com Agouti/genética , Animais , Antimetabólitos/farmacologia , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/metabolismo , Desoxiglucose/farmacologia , Técnicas de Silenciamento de Genes , Hipotálamo/citologia , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Masculino , Camundongos , Neurônios/metabolismo , Neuropeptídeo Y/genética , RNA Mensageiro/metabolismo
12.
Mol Metab ; 6(10): 1103-1112, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29031712

RESUMO

OBJECTIVE: The mitochondrial uncoupling agent 2,4-dinitrophenol (DNP), historically used as a treatment for obesity, is known to cross the blood-brain-barrier, but its effects on central neural circuits controlling body weight are largely unknown. As hypothalamic melanocortin neuropeptide Y/agouti-related protein (NPY/AgRP) and pro-opiomelanocortin (POMC) neurons represent key central regulators of food intake and energy expenditure we investigated the effects of DNP on these neurons, food intake and energy expenditure. METHOD: C57BL/6 and melanocortin-4 receptor (MC4R) knock-out mice were administered DNP intracerebroventricularly (ICV) and the metabolic changes were characterized. The specific role of NPY and POMC neurons and the ionic mechanisms mediating the effects of uncoupling were examined with in vitro electrophysiology performed on NPY hrGFP or POMC eGFP mice. RESULTS: Here we show DNP-induced differential effects on melanocortin neurons including inhibiting orexigenic NPY and activating anorexigenic POMC neurons through independent ionic mechanisms coupled to mitochondrial function, consistent with an anorexigenic central effect. Central administration of DNP induced weight-loss, increased BAT thermogenesis and browning of white adipose tissue, and decreased food intake, effects that were absent in MC4R knock-out mice and blocked by the MC4R antagonist, AgRP. CONCLUSION: These data show a novel central anti-obesity mechanism of action of DNP and highlight the potential for selective melanocortin mitochondrial uncoupling to target metabolic disorders.


Assuntos
2,4-Dinitrofenol/farmacologia , Neuropeptídeo Y/metabolismo , Pró-Opiomelanocortina/metabolismo , Tecido Adiposo Marrom/metabolismo , Animais , Peso Corporal/efeitos dos fármacos , Ingestão de Alimentos/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Masculino , Melanocortinas/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/metabolismo , Mitocôndrias/fisiologia , Neurônios/efeitos dos fármacos , Obesidade/metabolismo , Receptor Tipo 4 de Melanocortina/metabolismo , Receptores de Melanocortina/fisiologia , Termogênese/fisiologia , Proteína Desacopladora 1/efeitos dos fármacos , Proteína Desacopladora 1/fisiologia , Redução de Peso
14.
Cell Metab ; 26(2): 375-393.e7, 2017 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-28768176

RESUMO

Beige adipocytes can interconvert between white and brown-like states and switch between energy storage versus expenditure. Here we report that beige adipocyte plasticity is important for feeding-associated changes in energy expenditure and is coordinated by the hypothalamus and the phosphatase TCPTP. A fasting-induced and glucocorticoid-mediated induction of TCPTP, inhibited insulin signaling in AgRP/NPY neurons, repressed the browning of white fat and decreased energy expenditure. Conversely feeding reduced hypothalamic TCPTP, to increase AgRP/NPY neuronal insulin signaling, white adipose tissue browning and energy expenditure. The feeding-induced repression of hypothalamic TCPTP was defective in obesity. Mice lacking TCPTP in AgRP/NPY neurons were resistant to diet-induced obesity and had increased beige fat activity and energy expenditure. The deletion of hypothalamic TCPTP in obesity restored feeding-induced browning and increased energy expenditure to promote weight loss. Our studies define a hypothalamic switch that coordinates energy expenditure with feeding for the maintenance of energy balance.


Assuntos
Ingestão de Alimentos/psicologia , Metabolismo Energético/fisiologia , Hipotálamo/metabolismo , Proteína Tirosina Fosfatase não Receptora Tipo 2/biossíntese , Proteína Relacionada com Agouti/genética , Proteína Relacionada com Agouti/metabolismo , Animais , Camundongos , Camundongos Transgênicos , Neuropeptídeo Y/genética , Neuropeptídeo Y/metabolismo , Obesidade/genética , Obesidade/metabolismo , Proteína Tirosina Fosfatase não Receptora Tipo 2/genética
15.
Biol Psychiatry ; 81(9): 797-806, 2017 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-26826876

RESUMO

BACKGROUND: There is increasing evidence that the pathological overeating underlying some forms of obesity is compulsive in nature and therefore contains elements of an addictive disorder. However, direct physiological evidence linking obesity to synaptic plasticity akin to that occurring in addiction is lacking. We sought to establish whether the propensity to diet-induced obesity (DIO) is associated with addictive-like behavior, as well as synaptic impairments in the nucleus accumbens core considered hallmarks of addiction. METHODS: Sprague Dawley rats were allowed free access to a palatable diet for 8 weeks then separated by weight gain into DIO-prone and DIO-resistant subgroups. Access to palatable food was then restricted to daily operant self-administration sessions using fixed ratio 1, 3, and 5 and progressive ratio schedules. Subsequently, nucleus accumbens brain slices were prepared, and we tested for changes in the ratio between α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate currents and the ability to exhibit long-term depression. RESULTS: We found that propensity to develop DIO is linked to deficits in the ability to induce long-term depression in the nucleus accumbens, as well as increased potentiation at these synapses as measured by AMPA/N-methyl-D-aspartate currents. Consistent with these impairments, we observed addictive-like behavior in DIO-prone rats, including 1) heightened motivation for palatable food; 2) excessive intake; and 3) increased food seeking when food was unavailable. CONCLUSIONS: Our results show overlap between the propensity for DIO and the synaptic changes associated with facets of addictive behavior, supporting partial coincident neurological underpinnings for compulsive overeating and drug addiction.


Assuntos
Comportamento Aditivo/fisiopatologia , Dieta , Plasticidade Neuronal , Núcleo Accumbens/fisiologia , Obesidade/fisiopatologia , Animais , Condicionamento Operante/fisiologia , Comportamento Alimentar , Ácido Glutâmico/fisiologia , Depressão Sináptica de Longo Prazo , Masculino , Ratos , Ratos Sprague-Dawley , Receptores de AMPA/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia
16.
Br J Pharmacol ; 173(9): 1438-51, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26773257

RESUMO

BACKGROUND AND PURPOSE: The 5-HT7 receptor is a GPCR that is the target of a broad range of antidepressant and antipsychotic drugs. Various studies have demonstrated an ability of the 5-HT7 receptor to modulate glutamatergic neurotransmission and cognitive processes although the potential impact upon AMPA receptors has not been investigated directly. The purposes of the present study were to investigate a direct modulation of the GluA1 AMPA receptor subunit and determine how this might influence AMPA receptor function. EXPERIMENTAL APPROACH: The influence of pharmacological manipulation of the 5-HT7 receptor system upon phosphorylation of GluA1 subunits was assessed by Western blotting of fractionated proteins from hippocampal neurones in culture (or proteins resident at the neurone surface) and the functional impact assessed by electrophysiological recordings in rat hippocampus in vitro and in vivo. KEY RESULTS: 5-HT7 receptor activation increased cAMP and relative pCREB levels in cultures of rat hippocampal neurones along with an increase in phosphorylation (Ser845) of the GluA1 AMPA receptor subunit evident in whole neurone extracts and within the neurone surface compartment. Electrophysiological recordings in rat hippocampus demonstrated a 5-HT7 receptor-mediated increase in AMPA receptor-mediated neurotransmission in vitro and in vivo. CONCLUSIONS AND IMPLICATIONS: The 5-HT7 receptor-mediated phosphorylation of the GluA1 AMPA receptor provides a molecular mechanism consistent with the 5-HT7 receptor-mediated increase in AMPA receptor-mediated neurotransmission.


Assuntos
Hipocampo/metabolismo , Subunidades Proteicas/metabolismo , Receptores de AMPA/química , Receptores de AMPA/metabolismo , Receptores de Serotonina/metabolismo , Transmissão Sináptica , Animais , Fosforilação , Ratos
17.
Neuropharmacology ; 100: 124-30, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26025659

RESUMO

Bexarotene has been reported to reduce brain amyloid-ß (Aß) levels and to improve cognitive function in transgenic mouse models of Alzheimer's disease (AD). Four groups failed to fully replicate the primary results but the original authors claimed overall support for the general conclusions. Because of its potential clinical importance, the current work studied the effects of bexarotene using two animal species and highly relevant paradigms. Rats were tested for the ability of bexarotene to prevent changes induced by an Aß challenge in the form intracerebroventricular (i.c.v) administration of 7PA2 conditioned medium (7PA2 CM) which contains high levels of Aß species. Bexarotene had no effect on the long-term potentiation of evoked extracellular field excitatory postsynaptic potentials induced by i.c.v. 7PA2 CM. It also had no effect following subcutaneous administration of 2, 5, 10 and 15 mg/kg on behavioral/cognitive impairment using an alternating-lever cyclic-ratio schedule of operant responding in the rat. The effects of bexarotene were further tested using the APPSwFILon, PSEN1*M146L*L286V transgenic mouse model of AD, starting at the time Aß deposits first begin to develop. Mice were sacrificed after 48 days of exposure to 100 mg bexarotene per day. No significant difference between test and control mice was found using a water-maze test, and no significant difference in the number of Aß deposits in cerebral cortex, using two different antibodies, was apparent. These results question the potential efficacy of bexarotene for AD treatment, even if instigated in the preclinical period prior to the onset of cognitive deficits reported for human AD. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.


Assuntos
Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Região CA1 Hipocampal/efeitos dos fármacos , Tetra-Hidronaftalenos/administração & dosagem , Doença de Alzheimer/induzido quimicamente , Doença de Alzheimer/fisiopatologia , Doença de Alzheimer/prevenção & controle , Peptídeos beta-Amiloides/toxicidade , Animais , Bexaroteno , Região CA1 Hipocampal/metabolismo , Região CA1 Hipocampal/fisiopatologia , Células CHO , Condicionamento Operante/efeitos dos fármacos , Cricetulus , Meios de Cultivo Condicionados , Modelos Animais de Doenças , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciação de Longa Duração/efeitos dos fármacos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Camundongos Transgênicos , Ratos , Ratos Sprague-Dawley
18.
Neuropharmacology ; 89: 122-35, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25242737

RESUMO

This study aimed at evaluating the effects of eslicarbazepine, carbamazepine (CBZ), oxcarbazepine (OXC) and lacosamide (LCM) on the fast and slow inactivated states of voltage-gated sodium channels (VGSC). The anti-epileptiform activity was evaluated in mouse isolated hippocampal slices. The anticonvulsant effects were evaluated in MES and the 6-Hz psychomotor tests. The whole-cell patch-clamp technique was used to investigate the effects of eslicarbazepine, CBZ, OXC and LCM on sodium channels endogenously expressed in N1E-115 mouse neuroblastoma cells. CBZ and eslicarbazepine exhibit similar concentration dependent suppression of epileptiform activity in hippocampal slices. In N1E-115 mouse neuroblastoma cells, at a concentration of 250 µM, the voltage dependence of the fast inactivation was not influenced by eslicarbazepine, whereas LCM, CBZ and OXC shifted the V0.5 value (mV) by -4.8, -12.0 and -16.6, respectively. Eslicarbazepine- and LCM-treated fast-inactivated channels recovered similarly to control conditions, whereas CBZ- and OXC-treated channels required longer pulses to recover. CBZ, eslicarbazepine and LCM shifted the voltage dependence of the slow inactivation (V0.5, mV) by -4.6, -31.2 and -53.3, respectively. For eslicarbazepine, LCM, CBZ and OXC, the affinity to the slow inactivated state was 5.9, 10.4, 1.7 and 1.8 times higher than to the channels in the resting state, respectively. In conclusion, eslicarbazepine did not share with CBZ and OXC the ability to alter fast inactivation of VGSC. Both eslicarbazepine and LCM reduce VGSC availability through enhancement of slow inactivation, but LCM demonstrated higher interaction with VGSC in the resting state and with fast inactivation gating.


Assuntos
Acetamidas/farmacologia , Carbamazepina/análogos & derivados , Carbamazepina/farmacologia , Dibenzazepinas/farmacologia , Canais de Sódio Disparados por Voltagem/fisiologia , Animais , Anticonvulsivantes/farmacologia , Linhagem Celular Tumoral , Relação Dose-Resposta a Droga , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Lacosamida , Masculino , Camundongos , Técnicas de Cultura de Órgãos , Oxcarbazepina , Fatores de Tempo
19.
Cell ; 159(6): 1404-16, 2014 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-25480301

RESUMO

Obesity is associated with increased blood pressure (BP), which in turn increases the risk of cardiovascular diseases. We found that the increase in leptin levels seen in diet-induced obesity (DIO) drives an increase in BP in rodents, an effect that was not seen in animals deficient in leptin or leptin receptors (LepR). Furthermore, humans with loss-of-function mutations in leptin and the LepR have low BP despite severe obesity. Leptin's effects on BP are mediated by neuronal circuits in the dorsomedial hypothalamus (DMH), as blocking leptin with a specific antibody, antagonist, or inhibition of the activity of LepR-expressing neurons in the DMH caused a rapid reduction of BP in DIO mice, independent of changes in weight. Re-expression of LepRs in the DMH of DIO LepR-deficient mice caused an increase in BP. These studies demonstrate that leptin couples changes in weight to changes in BP in mammalian species.


Assuntos
Hipertensão/metabolismo , Leptina/metabolismo , Obesidade/metabolismo , Animais , Leptina/genética , Camundongos Endogâmicos C57BL , Mutação , Neurônios/metabolismo , Obesidade/patologia , Receptores para Leptina/genética , Receptores para Leptina/metabolismo , Transdução de Sinais
20.
Curr Protoc Pharmacol ; 66: 11.15.1-11.15.26, 2014 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-25181009

RESUMO

Neuropathic pain develops following nerve injury, and is a chronic pain syndrome that can persist long after repair of a wound or removal of the neurological insult. This condition remains poorly treated, not least because of a lack of mechanism-based therapeutics. Clinically, neuropathic pain is characterized by three major symptoms: thermal or mechanical allodynia (pain sensation in response to previously non-noxious stimuli); hyperalgesia (enhanced pain sensation to noxious stimulation); and spontaneous, ongoing pain. These clinical symptoms can be modeled in rodent neuropathic pain models using behavioral and electrophysiological readouts. This unit describes techniques designed to record pathophysiological electrical activity associated with neuropathic pain at the level of the periphery, in single fibers of primary sensory neurons, and from wide dynamic range (WDR) neurons of the dorsal horn of the spinal cord. These techniques can be employed in both naïve animals and in animal models of neuropathy to investigate fundamental mechanisms contributing to the neuropathic pain state and the site, mode, and mechanism of action of putative analgesics.


Assuntos
Modelos Animais de Doenças , Neuralgia/fisiopatologia , Potenciais de Ação/fisiologia , Animais , Técnicas Eletrofisiológicas Cardíacas , Fenômenos Eletrofisiológicos/fisiologia , Masculino , Nervos Periféricos/fisiopatologia , Nervos Periféricos/cirurgia , Células do Corno Posterior/fisiologia , Ratos , Ratos Sprague-Dawley , Medula Espinal/fisiopatologia
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