RESUMO
Dysfunction of medial prefrontal cortex (mPFC) in association with imbalance of inhibitory and excitatory neurotransmission has been implicated in depression. However, the precise cellular mechanisms underlying this imbalance, particularly for GABAergic transmission in the mPFC, and the link with the rapid acting antidepressant ketamine remains poorly understood. Here we determined the influence of chronic unpredictable stress (CUS), an ethologically validated model of depression, on synaptic markers of GABA neurotransmission, and the influence of a single dose of ketamine on CUS-induced synaptic deficits in mPFC of male rodents. The results demonstrate that CUS decreases GABAergic proteins and the frequency of inhibitory post synaptic currents (IPSCs) of layer V mPFC pyramidal neurons, concomitant with depression-like behaviors. In contrast, a single dose of ketamine can reverse CUS-induced deficits of GABA markers, in conjunction with reversal of CUS-induced depressive-like behaviors. These findings provide further evidence of impairments of GABAergic synapses as key determinants of depressive behavior and highlight ketamine-induced synaptic responses that restore GABA inhibitory, as well as glutamate neurotransmission.
Assuntos
Antidepressivos/administração & dosagem , Depressão/fisiopatologia , Ketamina/administração & dosagem , Neurônios/efeitos dos fármacos , Córtex Pré-Frontal/efeitos dos fármacos , Estresse Psicológico/fisiopatologia , Transmissão Sináptica/efeitos dos fármacos , Ácido gama-Aminobutírico/fisiologia , Animais , Modelos Animais de Doenças , Potenciais Pós-Sinápticos Inibidores/efeitos dos fármacos , Masculino , Camundongos Endogâmicos C57BL , Neurônios/fisiologia , Córtex Pré-Frontal/fisiopatologiaRESUMO
Organismal stress initiates a tightly orchestrated set of responses involving complex physiological and neurocognitive systems. Here, we present evidence for glucagon-like peptide 1 (GLP-1)-mediated paraventricular hypothalamic circuit coordinating the global stress response. The GLP-1 receptor (Glp1r) in mice was knocked down in neurons expressing single-minded 1, a transcription factor abundantly expressed in the paraventricular nucleus (PVN) of the hypothalamus. Mice with single-minded 1-mediated Glp1r knockdown had reduced hypothalamic-pituitary-adrenal axis responses to both acute and chronic stress and were protected against weight loss associated with chronic stress. In addition, regional Glp1r knockdown attenuated stress-induced cardiovascular responses accompanied by decreased sympathetic drive to the heart. Finally, Glp1r knockdown reduced anxiety-like behavior, implicating PVN GLP-1 signaling in behavioral stress reactivity. Collectively, these findings support a circuit whereby brainstem GLP-1 activates PVN signaling to mount an appropriate whole-organism response to stress. These results raise the possibility that dysfunction of this system may contribute to stress-related pathologies, and thereby provide a novel target for intervention. SIGNIFICANCE STATEMENT: Dysfunctional stress responses are linked to a number of somatic and psychiatric diseases, emphasizing the importance of precise neuronal control of effector pathways. Pharmacological evidence suggests a role for glucagon-like peptide-1 (GLP-1) in modulating stress responses. Using a targeted knockdown of the GLP-1 receptor in the single-minded 1 neurons, we show dependence of paraventricular nucleus GLP-1 signaling in the coordination of neuroendocrine, autonomic, and behavioral responses to acute and chronic stress. To our knowledge, this is the first direct demonstration of an obligate brainstem-to-hypothalamus circuit orchestrating general stress excitation across multiple effector systems. These findings provide novel information regarding signaling pathways coordinating central control of whole-body stress reactivity.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Histona-Lisina N-Metiltransferase/genética , Proteínas Repressoras/genética , Transdução de Sinais/genética , Estresse Psicológico/fisiopatologia , Doença Aguda , Animais , Ansiedade/etiologia , Ansiedade/genética , Ansiedade/psicologia , Comportamento Animal , Doença Crônica , Ingestão de Alimentos , Receptor do Peptídeo Semelhante ao Glucagon 1/genética , Frequência Cardíaca/genética , Sistema Hipotálamo-Hipofisário/fisiopatologia , Masculino , Camundongos , Camundongos Knockout , Núcleo Hipotalâmico Paraventricular , Sistema Hipófise-Suprarrenal/fisiopatologia , Estresse Psicológico/psicologia , Natação/psicologiaRESUMO
Impaired fear extinction contributes to the persistence of post-traumatic stress disorder (PTSD), and can be utilized for the study of novel therapeutic agents. Glutamate plays an important role in the formation of traumatic memories, and in the pathophysiology and treatment of PTSD, highlighting several possible drug targets. Recent clinical studies demonstrate that infusion of ketamine, a glutamate NMDA receptor antagonist, rapidly and significantly reduces symptom severity in PTSD patients. In the present study, we examine the mechanisms underlying the actions of ketamine in a rodent model of fear conditioning, extinction, and renewal. Rats received ketamine or saline 24h after fear conditioning and were then subjected to extinction-training on each of the following three days. Ketamine administration enhanced extinction on the second day of training (i.e., reduced freezing behavior to cue) and produced a long-lasting reduction in freezing on exposure to cue plus context 8days later. Additionally, ketamine and extinction exposure increased levels of mTORC1 in the medial prefrontal cortex (mPFC), a region involved in the acquisition and retrieval of extinction, and infusion of the selective mTORC1 inhibitor rapamycin into the mPFC blocked the effects of ketamine on extinction. Ketamine plus extinction also increased cFos in the mPFC and administration of a glutamate-AMPA receptor antagonist blocked the effects of ketamine. These results support the hypothesis that ketamine produces long-lasting mTORC1/protein synthesis and activity dependent effects on neuronal circuits that enhance the expression of extinction and could represent a novel approach for the treatment of PTSD.
Assuntos
Extinção Psicológica/efeitos dos fármacos , Medo/efeitos dos fármacos , Ketamina/farmacologia , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Memória/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Animais , Condicionamento Clássico/fisiologia , Medo/fisiologia , Masculino , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/efeitos dos fármacos , Receptores de N-Metil-D-Aspartato/metabolismo , Transtornos de Estresse Pós-Traumáticos/tratamento farmacológicoRESUMO
PURPOSE OF REVIEW: Posttraumatic stress disorder (PTSD) is characterized by hyperarousal and recurrent stressful memories after an emotionally traumatic event. Extensive research has been conducted to identify the neurobiological determinants that underlie the pathophysiology of PTSD. In this review, we examine evidence regarding the molecular and cellular pathophysiology of PTSD focusing on two primary brain regions: the vmPFC and the amygdala. RECENT FINDINGS: This discussion includes a review of the molecular alterations related to PTSD, focusing mainly on changes to glucocorticoid receptor signaling. We also examine postmortem gene expression studies that have been conducted to date and the molecular changes that have been observed in peripheral blood studies of PTSD patients. Causal, mechanistic evidence is difficult to obtain in human studies, so we also review preclinical models of PTSD. Integration of peripheral blood and postmortem studies with preclinical models of PTSD has begun to reveal the molecular changes occurring in patients with PTSD. These findings indicate that the pathophysiology of PTSD includes disruption of glucocorticoid signaling and inflammatory systems and occurs at the level of altered gene expression. We will assess the impact of these findings on the future of PTSD molecular research.
Assuntos
Encéfalo/metabolismo , Encéfalo/fisiopatologia , Glucocorticoides/metabolismo , Transdução de Sinais/fisiologia , Transtornos de Estresse Pós-Traumáticos/metabolismo , Transtornos de Estresse Pós-Traumáticos/fisiopatologia , Animais , Genômica , Humanos , Inflamação/fisiopatologia , RatosRESUMO
Chronic stress causes hypothalamo-pituitary-adrenal (HPA) axis hyperactivity and cardiovascular dyshomeostasis. Noradrenergic (NA) neurons in the nucleus of the solitary tract (NTS) are considered to play a role in these changes. In this study, we tested the hypothesis that NTS NA A2 neurons are required for cardiovascular and HPA axis responses to both acute and chronic stress. Adult male rats received bilateral microinjection into the NTS of 6-hydroxydopamine (6-OHDA) to lesion A2 neurons [cardiovascular study, n = 5; HPA study, n = 5] or vehicle [cardiovascular study, n = 6; HPA study, n = 4]. Rats were exposed to acute restraint stress followed by 14 d of chronic variable stress (CVS). On the last day of testing, rats were placed in a novel elevated plus maze (EPM) to test post-CVS stress responses. Lesions of NTS A2 neurons reduced the tachycardic response to acute restraint, confirming that A2 neurons promote sympathetic activation following acute stress. In addition, CVS increased the ratio of low-frequency to high-frequency power for heart rate variability, indicative of sympathovagal imbalance, and this effect was significantly attenuated by 6-OHDA lesion. Lesions of NTS A2 neurons reduced acute restraint-induced corticosterone secretion, but did not affect the corticosterone response to the EPM, indicating that A2 neurons promote acute HPA axis responses, but are not involved in CVS-mediated HPA axis sensitization. Collectively, these data indicate that A2 neurons promote both cardiovascular and HPA axis responses to acute stress. Moreover, A2 catecholaminergic neurons may contribute to the potentially deleterious enhancement of sympathetic drive following chronic stress.
Assuntos
Neurônios Adrenérgicos/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Oxidopamina/farmacologia , Núcleo Solitário/efeitos dos fármacos , Estresse Fisiológico/efeitos dos fármacos , Simpatolíticos/farmacologia , Neurônios Adrenérgicos/fisiologia , Animais , Sistema Cardiovascular , Corticosterona/metabolismo , Frequência Cardíaca/fisiologia , Sistema Hipotálamo-Hipofisário/efeitos dos fármacos , Sistema Hipotálamo-Hipofisário/metabolismo , Masculino , Sistema Hipófise-Suprarrenal/efeitos dos fármacos , Sistema Hipófise-Suprarrenal/metabolismo , Ratos , Ratos Sprague-Dawley , Núcleo Solitário/citologia , Núcleo Solitário/fisiologia , Estresse Fisiológico/fisiologia , Estresse PsicológicoRESUMO
The nucleus accumbens (NAc) is a brain hub regulating motivated behaviors, including social competitiveness. Mitochondrial function in the NAc links anxiety with social competitiveness, and the mitochondrial fusion protein mitofusin 2 (Mfn2) in NAc neurons regulates anxiety-related behaviors. However, it remains unexplored whether accumbal Mfn2 levels also affect social behavior and whether Mfn2 actions in the emotional and social domain are driven by distinct cell types. Here, we found that subordinate-prone highly anxious rats show decreased accumbal Mfn2 levels and that Mfn2 overexpression promotes dominant behavior. In mice, selective Mfn2 downregulation in NAc dopamine D2 receptor-expressing medium spiny neurons (D2-MSNs) induced social subordination, accompanied by decreased accumbal mitochondrial functions and decreased excitability in D2-MSNs. Instead, D1-MSN-targeted Mfn2 downregulation affected competitive ability only transiently and likely because of an increase in anxiety-like behaviors. Our results assign dissociable cell-type specific roles to Mfn2 in the NAc in modulating social dominance and anxiety.
Assuntos
GTP Fosfo-Hidrolases , Proteínas Mitocondriais , Neurônios , Núcleo Accumbens , Animais , Camundongos , Ratos , Encéfalo/metabolismo , Hidrolases/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios/metabolismo , Núcleo Accumbens/metabolismo , Receptores de Dopamina D1/metabolismo , Predomínio Social , GTP Fosfo-Hidrolases/metabolismo , Proteínas Mitocondriais/metabolismoRESUMO
Obesity is frequently associated with impairments in the social domain, and stress at puberty can lead to long-lasting changes in visceral fat deposition and in social behaviors. However, whether stress-induced changes in adipose tissue can affect fat-to-brain signaling, thereby orchestrating behavioral changes, remains unknown. We found that peripubertally stressed male-but not female-mice exhibit concomitant increased adiposity and sociability deficits. We show that reduced levels of the adipokine nicotinamide phosphoribosyltransferase (NAMPT) in fat and its extracellular form eNAMPT in blood contribute to lifelong reductions in sociability induced by peripubertal stress. By using a series of adipose tissue and brain region-specific loss- and gain-of-function approaches, we implicate impaired nicotinamide adenine dinucleotide (NAD+)/SIRT1 pathway in the nucleus accumbens. Impairments in sociability and accumbal neuronal excitability are prevented by normalization of eNAMPT levels or treatment with nicotinamide mononucleotide (NMN), a NAD+-boosting compound. We propose NAD+ boosters to treat social deficits of early life stress origin.
RESUMO
BACKGROUND: Emerging evidence points to a central role of mitochondria in psychiatric disorders. However, little is known about the molecular players that regulate mitochondria in neural circuits regulating anxiety and depression and about how they impact neuronal structure and function. Here, we investigated the role of molecules involved in mitochondrial dynamics in medium spiny neurons (MSNs) from the nucleus accumbens (NAc), a hub of the brain's motivation system. METHODS: We assessed how individual differences in anxiety-like (measured via the elevated plus maze and open field tests) and depression-like (measured via the forced swim and saccharin preference tests) behaviors in outbred rats relate to mitochondrial morphology (electron microscopy and 3-dimensional reconstructions) and function (mitochondrial respirometry). Mitochondrial molecules were measured for protein (Western blot) and messenger RNA (quantitative reverse transcriptase polymerase chain reaction, RNAscope) content. Dendritic arborization (Golgi Sholl analyses), spine morphology, and MSN excitatory inputs (patch-clamp electrophysiology) were characterized. MFN2 overexpression in the NAc was induced through an AAV9-syn1-MFN2. RESULTS: Highly anxious animals showed increased depression-like behaviors, as well as reduced expression of the mitochondrial GTPase MFN2 in the NAc. They also showed alterations in mitochondria (i.e., respiration, volume, and interactions with the endoplasmic reticulum) and MSNs (i.e., dendritic complexity, spine density and typology, and excitatory inputs). Viral MFN2 overexpression in the NAc reversed all of these behavioral, mitochondrial, and neuronal phenotypes. CONCLUSIONS: Our results implicate a causal role for accumbal MFN2 on the regulation of anxiety and depression-like behaviors through actions on mitochondrial and MSN structure and function. MFN2 is posited as a promising therapeutic target to treat anxiety and associated behavioral disturbances.
Assuntos
Depressão , Núcleo Accumbens , Animais , Ansiedade , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias , Neurônios/metabolismo , Núcleo Accumbens/metabolismo , RatosRESUMO
Mitochondrial dysfunction was highlighted as a crucial vulnerability factor for the development of depression. However, systemic studies assessing stress-induced changes in mitochondria-associated genes in brain regions relevant to depression symptomatology remain scarce. Here, we performed a genome-wide transcriptomic study to examine mitochondrial gene expression in the prefrontal cortex (PFC) and nucleus accumbens (NAc) of mice exposed to multimodal chronic restraint stress. We identified mitochondria-associated gene pathways as most prominently affected in the PFC and with lesser significance in the NAc. A more detailed mitochondrial gene expression analysis revealed that in particular mitochondrial DNA-encoded subunits of the oxidative phosphorylation complexes were altered in the PFC. The comparison of our data with a reanalyzed transcriptome data set of chronic variable stress mice and major depression disorder subjects showed that the changes in mitochondrial DNA-encoded genes are a feature generalizing to other chronic stress-protocols as well and might have translational relevance. Finally, we provide evidence for changes in mitochondrial outputs in the PFC following chronic stress that are indicative of mitochondrial dysfunction. Collectively, our work reinforces the idea that changes in mitochondrial gene expression are key players in the prefrontal adaptations observed in individuals with high behavioral susceptibility and resilience to chronic stress.
Assuntos
Suscetibilidade a Doenças/metabolismo , Mitocôndrias/metabolismo , Córtex Pré-Frontal/metabolismo , Estresse Psicológico/metabolismo , Animais , Perfilação da Expressão Gênica , Hormônio Liberador de Gonadotropina/análogos & derivados , Masculino , Camundongos Endogâmicos C57BL , Mitocôndrias/genética , Núcleo Accumbens/metabolismo , Núcleo Accumbens/fisiopatologia , Córtex Pré-Frontal/fisiopatologia , Resiliência Psicológica , Transcriptoma/fisiologiaRESUMO
The T cell death-associated gene 8 (TDAG8) is a pH-sensing GPCR with a reported immune-specific expression profile. Here, we demonstrate pH-induced activation of TDAG8 receptor cloned from rodent brain (rTDAG8). Cloned rTDAG8 transcript showed 88-95% homology with human and mouse transcripts of lymphoid origin. RT-PCR revealed high expression of TDAG8 in forebrain limbic regions. Extracellular acidification induced significantly elevated intracellular cyclic AMP, and phosphorylated CREB in TDAG8 expressing cells. Acidification-induced LDH release was significantly attenuated in cells expressing TDAG8, suggesting neuroprotective potential against acidosis-related cell injury. Our results open up new areas of investigation into the relevance of TDAG8 in pH homeostasis and pathological states associated with acid-base dys-regulation in the brain such as ischemia and panic disorder.
Assuntos
Equilíbrio Ácido-Base , Prosencéfalo/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Sequência de Aminoácidos , Animais , Isquemia Encefálica/metabolismo , Sobrevivência Celular , Clonagem Molecular , AMP Cíclico/metabolismo , Concentração de Íons de Hidrogênio , Masculino , Dados de Sequência Molecular , Transtorno de Pânico/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores Acoplados a Proteínas G/genética , Transdução de SinaisRESUMO
The two stress-responsive physiological systems, autonomic nervous system (ANS) and hypothalamus-pituitary-adrenal (HPA) axis exert complementary and interrelated actions in the organism. Individuals that suffer stress-related psychopathologies frequently present simultaneous alterations -i.e., either low or high- responsiveness- in both systems. However, there is scarce evidence establishing whether a priori alterations in these systems -i.e., independent of previous stress exposure- may predispose to the development of psychopathologies possibly due to the lack of animal models simultaneously involving aberrant HPA and SNS responses. In this study, we describe two animal models selectively bred according to their differential (either high, 'High', or low, 'Low') glucocorticoid responsiveness to stress, in comparison to a third line of rats that displays intermediate ('Inter') glucocorticoid responses. The two extreme lines may be considered distinct models of psychopathology; the High line representing a model of constitutive mood alterations while the Low line a model of vulnerability to develop stress-induced psychopathologies. We recorded the electrocardiogram in rats from the three lines and quantified heart rate variability and vagal tone indexes during rest and stress challenges. Rats from both High and Low lines displayed higher heart rate and lower basal vagal tone than the Inter group, both at resting and following stress exposure. Specific pharmacological manipulations probing the relative contribution of sympathetic and parasympathetic components on HR modulation confirmed a relative lower vagal tone in High and Low lines and discarded differences in the sympathetic regulation of heart rate between the lines. Therefore, the two genetically-selected High and Low glucocorticoid rat lines emerge as two valuable preclinical models of psychopathology involving two key risk factors for psychiatric and cardiovascular disorders, namely dysregulations in the HPA axis and cardiac vagal functioning.
Assuntos
Estresse Fisiológico/fisiologia , Estresse Psicológico/fisiopatologia , Nervo Vago/fisiopatologia , Adaptação Psicológica/fisiologia , Animais , Sistema Nervoso Autônomo/fisiopatologia , Corticosterona , Glucocorticoides/metabolismo , Glucocorticoides/farmacologia , Frequência Cardíaca/fisiologia , Sistema Hipotálamo-Hipofisário/fisiopatologia , Masculino , Transtornos do Humor/fisiopatologia , Sistema Hipófise-Suprarrenal/fisiopatologia , Psicopatologia/métodos , Ratos , Ratos WistarRESUMO
γ-aminobutyric acid (GABA) inhibitory interneurons play a key role in efferent and afferent control of principle neuron activity in the prefrontal cortex (PFC), thereby regulating signal integrity of cognitive and behavioral processes. Recent evidence suggests that specific subtypes of interneurons in the PFC mediate stress-induced depressive-like behaviors. Abnormalities of GABA interneurons, particularly the somatostatin (human, SST; mouse, Sst) subtype, have been reported in postmortem brains of depressed subjects and include sex differences that could explain the increased incidence of depression in women. Here, we analyze the transcriptional profiles and the effects of chronic stress in males vs. females on GABA interneuron subtypes in the PFC. Using Sst- and Parvalbumin-fluorescence tagged reporter mice and fluorescence-activated cell sorting (FACS) combined with RNA sequencing, we identify distinct transcriptome profiles for these interneuron subtypes in the medial PFC. Based on evidence that SST interneurons are altered in depression, we then determined the effects of chronic stress on this interneuron subtype. Chronic stress causes significant dysregulation of several key pathways, including sex-specific differences in the Sst interneuron profiles. The transcriptional pathways altered by chronic stress in males overlap with enriched pathways in non-stressed females. These changes occurred predominantly in decreased expression of elongation initiation factor 2 (EIF2) signaling, suggesting that dysfunction of the translational machinery of SST interneurons could be critical to the development of depressive-like behaviors in males. In addition, SST interneurons from females exposed to chronic stress show dysregulation of different, growth factor signaling pathways.
Assuntos
Interneurônios/metabolismo , Córtex Pré-Frontal/patologia , Somatostatina/metabolismo , Estresse Psicológico/patologia , Ácido gama-Aminobutírico/metabolismo , Animais , Feminino , Masculino , Camundongos , Rede Nervosa/metabolismo , Rede Nervosa/patologia , Parvalbuminas/metabolismo , Córtex Pré-Frontal/citologia , Fatores Sexuais , TranscriptomaRESUMO
BACKGROUND: Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology and treatment of depression. Recent clinical studies demonstrate that scopolamine, a nonselective muscarinic acetylcholine receptor antagonist, produces rapid antidepressant effects in patients with depression. Rodent studies demonstrate that scopolamine increases glutamate transmission and synaptogenesis in the medial prefrontal cortex (mPFC). Here we tested the hypothesis that activity-dependent BDNF release within the mPFC is necessary for the antidepressant actions of scopolamine. METHODS: Behavioral effects of scopolamine were assessed in BDNF Val/Met knock-in mice, in which BDNF processing and release are impaired. In addition, intra-mPFC infusion of a BDNF-neutralizing antibody was performed to test the necessity of BDNF release in driving scopolamine-induced behavioral responses. Further in vivo and in vitro experiments were performed to delineate BDNF-dependent mechanisms underlying the effects of scopolamine. RESULTS: We found that BDNF Met/Met mice have attenuated responses to scopolamine and that anti-BDNF antibody infusions into the mPFC prevented the antidepressant-like behavioral effects of scopolamine. In vitro experiments show that scopolamine rapidly stimulates BDNF release and tropomyosin receptor kinase B-extracellular signal-regulated kinase signaling. Moreover, these effects require alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor activation and are blocked by neuronal silencing. Importantly, pretreatment with verapamil prevented scopolamine-induced behavioral responses and BDNF-tropomyosin receptor kinase B signaling, suggesting that these effects are dependent on activation of voltage-dependent calcium channels. CONCLUSIONS: The results identify an essential role for activity-dependent BDNF release in the rapid antidepressant effects of scopolamine. Attenuation of responses in BDNF Met mice indicates that patients with the Met allele may be less responsive to scopolamine.
Assuntos
Antidepressivos/farmacologia , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Transtorno Depressivo/tratamento farmacológico , Transtorno Depressivo/metabolismo , Escopolamina/farmacologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Encéfalo/patologia , Fator Neurotrófico Derivado do Encéfalo/genética , Canais de Cálcio Tipo L/metabolismo , Células Cultivadas , Transtorno Depressivo/patologia , Modelos Animais de Doenças , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Masculino , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Ratos Sprague-Dawley , Receptor Muscarínico M1/antagonistas & inibidores , Receptor Muscarínico M1/metabolismo , Receptor trkB/metabolismo , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismo , Fatores de Tempo , Verapamil/farmacologia , Ácido gama-Aminobutírico/metabolismoRESUMO
Ghrelin is a 28-amino acid polypeptide that regulates feeding, glucose metabolism, and emotionality (stress, anxiety, and depression). Plasma ghrelin circulates as desacyl ghrelin (DAG) or, in an acylated form, acyl ghrelin (AG), through the actions of ghrelin O-acyltransferase (GOAT), exhibiting low or high affinity, respectively, for the growth hormone secretagogue receptor (GHSR) 1a. We investigated the role of endogenous AG, DAG, and GHSR1a signaling on anxiety and stress responses using ghrelin knockout (Ghr KO), GOAT KO, and Ghsr stop-floxed (Ghsr null) mice. Behavioral and hormonal responses were tested in the elevated plus maze and light/dark (LD) box. Mice lacking both AG and DAG (Ghr KO) increased anxiety-like behaviors across tests, whereas anxiety reactions were attenuated in DAG-treated Ghr KO mice and in mice lacking AG (GOAT KO). Notably, loss of GHSR1a (Ghsr null) did not affect anxiety-like behavior in any test. Administration of AG and DAG to Ghr KO mice with lifelong ghrelin deficiency reduced anxiety-like behavior and decreased phospho-extracellular signal-regulated kinase phosphorylation in the Edinger-Westphal nucleus in wild-type mice, a site normally expressing GHSR1a and involved in stress- and anxiety-related behavior. Collectively, our data demonstrate distinct roles for endogenous AG and DAG in regulation of anxiety responses and suggest that the behavioral impact of ghrelin may be context dependent.
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Ansiolíticos/uso terapêutico , Ansiedade/tratamento farmacológico , Núcleo de Edinger-Westphal/efeitos dos fármacos , Grelina/uso terapêutico , Neurônios/efeitos dos fármacos , Aciltransferases/genética , Aciltransferases/metabolismo , Animais , Ansiedade/etiologia , Ansiedade/metabolismo , Ansiedade/patologia , Comportamento Animal/efeitos dos fármacos , Corticosterona/sangue , Núcleo de Edinger-Westphal/metabolismo , Núcleo de Edinger-Westphal/patologia , Grelina/genética , Grelina/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Proteínas de Membrana , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/metabolismo , Neurônios/patologia , Fosforilação/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Receptores de Grelina/genética , Receptores de Grelina/metabolismo , Restrição Física/efeitos adversos , Estresse Fisiológico/efeitos dos fármacos , Estresse Psicológico/fisiopatologiaRESUMO
Psychiatric diseases, notably major depression, are associated with imbalance of excitatory and inhibitory neurotransmission within the prefrontal cortex (PFC) and related limbic brain circuitry. In many cases these illnesses are precipitated or exacerbated by chronic stress, which also alters excitatory and inhibitory neurotransmitter systems. Notably, exposure to repeated uncontrollable stress causes persistent changes in the synaptic integrity and function of the principal glutamatergic excitatory neurons in the PFC, characterized by neuronal atrophy and loss of synaptic connections. This can lead to dysfunction of the PFC circuitry that is necessary for execution of adaptive behavioral responses. In addition, an emerging literature shows that chronic stress also causes extensive alteration of GABAergic inhibitory circuits in the PFC, leading to the hypothesis that inhibitory neurotransmitter deficits contribute to changes in PFC neuronal excitability and cognitive impairments. Here we review evidence in rodents and human, which point to the mechanisms underlying stress-induced alterations of GABA transmission in the PFC, and its relevance to circuit dysfunction in mood and stress related disorders. These findings suggest that alterations of GABA interneurons and inhibitory neurotransmission play a causal role in the development of stress-related neurobiological illness, and could identify a new line of GABA related therapeutic targets.
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Stress-associated disorders, including depression and anxiety, impact nearly 20% of individuals in the United States. The social, health, and economic burden imposed by stress-associated disorders requires in depth research efforts to identify suitable treatment strategies. Traditional medications (e.g., selective serotonin reuptake inhibitors, monoamine oxidase inhibitors) have significant limitations, notably a time lag for therapeutic response that is compounded by low rates of efficacy. Excitement over ketamine, a rapid acting antidepressant effective in treatment resistant patients, is tempered by transient dissociative and psychotomimetic effects, as well as abuse potential. Rodent stress models are commonly used to produce behavioral abnormalities that resemble those observed in stress-associated disorders. Stress models also produce molecular and cellular morphological changes in stress sensitive brain regions, including the prefrontal cortex and hippocampus that resemble alterations observed in depression. Rapid acting antidepressants such as ketamine can rescue stress-associated morphological and behavioral changes in rodent models. Here, we review the literature supporting a role for rapid acting antidepressants in opposing the effects of stress, and summarize research efforts seeking to elucidate the molecular, cellular, and circuit level targets of these agents.
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The hypothalamo-pituitary-adrenocortical (HPA) axis is required for stress adaptation. Activation of the HPA axis causes secretion of glucocorticoids, which act on multiple organ systems to redirect energy resources to meet real or anticipated demand. The HPA stress response is driven primarily by neural mechanisms, invoking corticotrophin releasing hormone (CRH) release from hypothalamic paraventricular nucleus (PVN) neurons. Pathways activating CRH release are stressor dependent: reactive responses to homeostatic disruption frequently involve direct noradrenergic or peptidergic drive of PVN neurons by sensory relays, whereas anticipatory responses use oligosynaptic pathways originating in upstream limbic structures. Anticipatory responses are driven largely by disinhibition, mediated by trans-synaptic silencing of tonic PVN inhibition via GABAergic neurons in the amygdala. Stress responses are inhibited by negative feedback mechanisms, whereby glucocorticoids act to diminish drive (brainstem) and promote transsynaptic inhibition by limbic structures (e.g., hippocampus). Glucocorticoids also act at the PVN to rapidly inhibit CRH neuronal activity via membrane glucocorticoid receptors. Chronic stress-induced activation of the HPA axis takes many forms (chronic basal hypersecretion, sensitized stress responses, and even adrenal exhaustion), with manifestation dependent upon factors such as stressor chronicity, intensity, frequency, and modality. Neural mechanisms driving chronic stress responses can be distinct from those controlling acute reactions, including recruitment of novel limbic, hypothalamic, and brainstem circuits. Importantly, an individual's response to acute or chronic stress is determined by numerous factors, including genetics, early life experience, environmental conditions, sex, and age. The context in which stressors occur will determine whether an individual's acute or chronic stress responses are adaptive or maladaptive (pathological).
Assuntos
Sistema Hipotálamo-Hipofisário/metabolismo , Sistema Hipófise-Suprarrenal/metabolismo , Estresse Fisiológico , Animais , Glucocorticoides/metabolismo , Homeostase , Humanos , Sistema Hipotálamo-Hipofisário/fisiologia , Sistema Hipófise-Suprarrenal/fisiologiaRESUMO
BACKGROUND: Multiple neuropsychiatric disorders, e.g., depression, are linked to imbalances in excitatory and inhibitory neurotransmission and prefrontal cortical dysfunction, and are concomitant with chronic stress. METHODS: We used electrophysiologic (n = 5-6 animals, 21-25 cells/group), neuroanatomic (n = 6-8/group), and behavioral (n = 12/group) techniques to test the hypothesis that chronic stress increases inhibition of medial prefrontal cortex (mPFC) glutamatergic output neurons. RESULTS: Using patch clamp recordings from infralimbic mPFC pyramidal neurons, we found that chronic stress selectively increases the frequency of miniature inhibitory postsynaptic currents with no effect on amplitude, which suggests that chronic stress increases presynaptic gamma-aminobutyric acid release. Elevated gamma-aminobutyric acid release under chronic stress is accompanied by increased inhibitory appositions and terminals onto glutamatergic cells, as assessed by both immunohistochemistry and electron microscopy. Furthermore, chronic stress decreases glucocorticoid receptor immunoreactivity specifically in a subset of inhibitory neurons, which suggests that increased inhibitory tone in the mPFC after chronic stress may be caused by loss of a glucocorticoid receptor-mediated brake on interneuron activity. These neuroanatomic and functional changes are associated with impairment of a prefrontal-mediated behavior. During chronic stress, rats initially make significantly more errors in the delayed spatial win-shift task, an mPFC-mediated behavior, which suggests a diminished impact of the mPFC on decision making. CONCLUSIONS: Taken together, the data suggest that chronic stress increases synaptic inhibition onto prefrontal glutamatergic output neurons, limiting the influence of the prefrontal cortex in control of stress reactivity and behavior. Thus, these data provide a mechanistic link among chronic stress, prefrontal cortical hypofunction, and behavioral dysfunction.
Assuntos
Comportamento Animal/fisiologia , Ácido Glutâmico/metabolismo , Inibição Neural/fisiologia , Córtex Pré-Frontal/metabolismo , Células Piramidais/metabolismo , Receptores de Glucocorticoides/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Doença Crônica , Modelos Animais de Doenças , Potenciais Pós-Sinápticos Inibidores/fisiologia , Masculino , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-DawleyRESUMO
BACKGROUND: Carbon dioxide (CO2) inhalation, a biological challenge and pathologic marker in panic disorder, evokes intense fear and panic attacks in susceptible individuals. The molecular identity and anatomic location of CO2-sensing systems that translate CO2-evoked fear remain unclear. We investigated contributions of microglial acid sensor T cell death-associated gene-8 (TDAG8) and microglial proinflammatory responses in CO2-evoked behavioral and physiological responses. METHODS: CO2-evoked freezing, autonomic, and respiratory responses were assessed in TDAG8-deficient ((-/-)) and wild-type ((+/+)) mice. Involvement of TDAG8-dependent microglial activation and proinflammatory cytokine interleukin (IL)-1ß with CO2-evoked responses was investigated using microglial blocker, minocycline, and IL-1ß antagonist IL-1RA. CO2-chemosensitive firing responses using single-cell patch clamping were measured in TDAG8(-/-) and TDAG8(+/+) mice to gain functional insights. RESULTS: TDAG8 expression was localized in microglia enriched within the sensory circumventricular organs. TDAG8(-/-) mice displayed attenuated CO2-evoked freezing and sympathetic responses. TDAG8 deficiency was associated with reduced microglial activation and proinflammatory cytokine IL-1ß within the subfornical organ. Central infusion of microglial activation blocker minocycline and IL-1ß antagonist IL-1RA attenuated CO2-evoked freezing. Finally, CO2-evoked neuronal firing in patch-clamped subfornical organ neurons was dependent on acid sensor TDAG8 and IL-1ß. CONCLUSIONS: Our data identify TDAG8-dependent microglial acid sensing as a unique chemosensor for detecting and translating hypercapnia to fear-associated behavioral and physiological responses, providing a novel mechanism for homeostatic threat detection of relevance to psychiatric conditions such as panic disorder.
Assuntos
Dióxido de Carbono/farmacologia , Células Quimiorreceptoras/fisiologia , Medo/efeitos dos fármacos , Microglia/efeitos dos fármacos , Microglia/fisiologia , Potenciais de Ação/fisiologia , Animais , Concentração de Íons de Hidrogênio , Resposta de Imobilidade Tônica/efeitos dos fármacos , Resposta de Imobilidade Tônica/fisiologia , Proteína Antagonista do Receptor de Interleucina 1 , Interleucina-1beta/antagonistas & inibidores , Interleucina-1beta/metabolismo , Masculino , Camundongos , Camundongos Knockout , Microglia/metabolismo , Microinjeções , Minociclina/administração & dosagem , Minociclina/farmacologia , Neurônios/fisiologia , Receptores Acoplados a Proteínas G/biossíntese , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiologia , Órgão Subfornical/metabolismoRESUMO
Studies focused on end-points that are confounded by stress are best performed under minimally stressful conditions. The objective of this study was to demonstrate the impact of handling designed to reduce animal stress on measurements of glucose tolerance. A cohort of mice (CD1.C57BL/6) naïve to any specific handling was subjected to either a previously described "cup" handling method, or a "tail-picked" method in which the animals were picked up by the tail (as is common for metabolic studies). Following training, an elevated plus maze (EPM) test was performed followed by measurement of blood glucose and plasma corticosterone. A second cohort (CD1.C57BL/6) was rendered obese by exposure to a high fat diet, handled with either the tail-picked or cup method and subjected to an intraperitoneal glucose tolerance test. A third cohort of C57BL/6 mice was exposed to a cup regimen that included a component of massage and was subjected to tests of anxiety-like behavior, glucose homeostasis, and corticosterone secretion. We found that the cup mice showed reduced anxiety-like behaviors in the EPM coupled with a reduction in blood glucose levels compared to mice handled by the tail-picked method. Additionally, cup mice on the high fat diet exhibited improved glucose tolerance compared to tail-picked controls. Finally, we found that the cup/massage group showed lower glucose levels following an overnight fast, and decreased anxiety-like behaviors associated with lower stress-induced plasma corticosterone concentration compared to tail-picked controls. These data demonstrate that application of handling methods that reduce anxiety-like behaviors in mice mitigates the confounding contribution of stress to interpretation of metabolic endpoints (such as glucose tolerance).