RESUMO
The etiology of depression is still poorly understood, but two major causative hypotheses have been put forth: the monoamine deficiency and the stress hypotheses of depression. We evaluate these hypotheses using animal models of endogenous depression and chronic stress. The endogenously depressed rat and its control strain were developed by bidirectional selective breeding from the Wistar-Kyoto (WKY) rat, an accepted model of major depressive disorder (MDD). The WKY More Immobile (WMI) substrain shows high immobility/despair-like behavior in the forced swim test (FST), while the control substrain, WKY Less Immobile (WLI), shows no depressive behavior in the FST. Chronic stress responses were investigated by using Brown Norway, Fischer 344, Lewis and WKY, genetically and behaviorally distinct strains of rats. Animals were either not stressed (NS) or exposed to chronic restraint stress (CRS). Genome-wide microarray analyses identified differentially expressed genes in hippocampi and amygdalae of the endogenous depression and the chronic stress models. No significant difference was observed in the expression of monoaminergic transmission-related genes in either model. Furthermore, very few genes showed overlapping changes in the WMI vs WLI and CRS vs NS comparisons, strongly suggesting divergence between endogenous depressive behavior- and chronic stress-related molecular mechanisms. Taken together, these results posit that although chronic stress may induce depressive behavior, its molecular underpinnings differ from those of endogenous depression in animals and possibly in humans, suggesting the need for different treatments. The identification of novel endogenous depression-related and chronic stress response genes suggests that unexplored molecular mechanisms could be targeted for the development of novel therapeutic agents.
Assuntos
Tonsila do Cerebelo/fisiopatologia , Transtorno Depressivo/patologia , Regulação da Expressão Gênica/fisiologia , Hipocampo/fisiopatologia , Estresse Psicológico/patologia , Corticosteroides/sangue , Glândulas Suprarrenais/patologia , Animais , Peso Corporal , Transtorno Depressivo/sangue , Transtorno Depressivo/genética , Modelos Animais de Doenças , Reação de Congelamento Cataléptica/fisiologia , Perfilação da Expressão Gênica , Masculino , Análise de Sequência com Séries de Oligonucleotídeos , Tamanho do Órgão , Radioimunoensaio , Ratos , Ratos Endogâmicos F344 , Ratos Endogâmicos WKY , Estresse Psicológico/sangue , Natação/psicologiaRESUMO
Corticotropin-releasing hormone (Crh), a 41-residue polypeptide, activates two G-protein-coupled receptors, Crhr1 and Crhr2, causing (among other transductional events) phosphorylation of the transcription factor Creb. The physiologic role of these receptors is only partially understood. Here we report that male, but not female, Crhr2-deficient mice exhibit enhanced anxious behaviour in several tests of anxiety in contrast to mice lacking Crhr1. The enhanced anxiety of Crhr2-deficient mice is not due to changes in hypothalamic-pituitary-adrenal (HPA) axis activity, but rather reflects impaired responses in specific brain regions involved in emotional and autonomic function, as monitored by a reduction of Creb phosphorylation in male, but not female, Crhr2-/- mice. We propose that Crhr2 predominantly mediates a central anxiolytic response, opposing the general anxiogenic effect of Crh mediated by Crhr1. Neither male nor female Crhr2-deficient mice show alterations of baseline feeding behaviour. Both respond with increased edema formation in response to thermal exposure, however, indicating that in contrast to its central role in anxiety, the peripheral role of Crhr2 in vascular permeability is independent of gender.
Assuntos
Ansiedade/genética , Deleção de Genes , Receptores de Hormônio Liberador da Corticotropina/genética , Hormônio Adrenocorticotrópico/sangue , Animais , Transtornos de Ansiedade/genética , Encéfalo/metabolismo , Corticosterona/sangue , Hormônio Liberador da Corticotropina/administração & dosagem , Hormônio Liberador da Corticotropina/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Edema/genética , Comportamento Alimentar/fisiologia , Feminino , Temperatura Alta/efeitos adversos , Sistema Hipotálamo-Hipofisário/fisiologia , Injeções Intraventriculares , Masculino , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/efeitos dos fármacos , Fosforilação , Sistema Hipófise-Suprarrenal/fisiologia , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Restrição Física , Fatores Sexuais , Estresse Fisiológico/sangue , Estresse Fisiológico/metabolismo , Estresse Fisiológico/fisiopatologia , Aumento de PesoRESUMO
African swine fever (ASF) is one of the most important diseases in pigs. Since there are no effective vaccines against the virus, farm biosecurity and good farming practices are the only effective tools to prevent the spread of the ASF virus (ASFV) in pig holdings. Hence, an important component of farm biosecurity is the Cleaning and Disinfection (C&D) procedure. Precise indications regarding the ideal disinfectant against ASFV are lacking, but every country has approved and/or authorized a list of biocides effective against ASFV. Lipidic solvents, which destroy the envelope of the virus and commercial disinfectants based on iodine and phenolic compounds are effective in inactivating the ASFV. This review describes the C&D protocol to apply in pig holdings with particular reference to ASFV.
Assuntos
Febre Suína Africana/prevenção & controle , Desinfecção , Abrigo para Animais/normas , Vírus da Febre Suína Africana , Animais , Microbiologia Ambiental , SuínosRESUMO
The differential modulation of learning and anxiety by corticotropin-releasing factor (CRF) through CRF receptor subtypes 1 (CRFR1) and 2 (CRFR2) is demonstrated. As learning paradigm, context- and tone-dependent fear conditioning of the mouse was used. Injection of CRF into the dorsal hippocampus before training enhanced learning through CRFR1 as demonstrated by the finding that this effect was prevented by the local injection of the unselective CRFR antagonist astressin, but not by the CRFR2-specific antagonist antisauvagine-30 (anti-Svg-30). In contrast, injection of CRF into the lateral intermediate septum impaired learning through CRFR2, as demonstrated by the ability of antisauvagine-30 to block this effect. When antisauvagine-30 was injected alone into the lateral intermediate septum, learning was enhanced. Such tonic control of learning was not observed when astressin or antisauvagine-30 was injected into the dorsal hippocampus. Injection of CRF after the training into the dorsal hippocampus and the lateral intermediate septum also enhanced and impaired learning, respectively. Thus, it was indicated that CRF acted on memory consolidation. It was concluded that the observed effects reflected changes of associative learning and not arousal, attention, or motivation. Although a dose of 20 pmol human/rat CRF was sufficient to affect learning significantly, a fivefold higher dose was required to induce anxiety by injection into the septum. Immobilization for 1 hr generated a stress response that included the induction of anxiety through septal CRFR2 and the subsequent enhancement of learning through hippocampal CRFR1. The involvement of either receptor subtype was demonstrated by region-specific injections of astressin and antisauvagine-30.
Assuntos
Ansiedade/fisiopatologia , Condicionamento Psicológico/fisiologia , Receptores de Hormônio Liberador da Corticotropina/fisiologia , Estresse Psicológico/fisiopatologia , Estimulação Acústica , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Química Encefálica/fisiologia , Condicionamento Psicológico/efeitos dos fármacos , Hormônio Liberador da Corticotropina/farmacologia , Relação Dose-Resposta a Droga , Medo/fisiologia , Hipocampo/química , Hipocampo/fisiologia , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Camundongos , Camundongos Endogâmicos BALB C , Fármacos Neuroprotetores/farmacologia , Fragmentos de Peptídeos/farmacologia , Receptores de Hormônio Liberador da Corticotropina/agonistas , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , Núcleos Septais/química , Núcleos Septais/fisiologiaRESUMO
Research into the biology of corticotropin-releasing factor (CRF) has been intensified significantly by the structural characterization of the CRF receptor (CRF-R). Two receptor subtypes, CRF-R1 and CRF-R2, and three functional splice variants of CRF-R2 have been discovered. It appears that ligand binding requires interaction of the N-terminal domain with one or two other extracellular domains of the CRF-R. In contrast to the mammalian CRF-R1, the frog CRF-R1 discriminates between naturally occurring CRF-like peptides.
RESUMO
In patients suffering from post-traumatic stress disorder (PTSD), fear evoked by trauma-related memories lasts long past the traumatic event and it is often complicated by general anxiety and depressed mood. This poses a treatment challenge, as drugs beneficial for some symptoms might exacerbate others. For example, in preclinical studies, antagonists of the NR2B subunit of N-methyl-d-aspartate receptors and activators of cAMP-dependent protein kinase (PKA) act as potent antidepressants and anxiolytics, but they block fear extinction. Using mice, we attempted to overcome this problem by interfering with individual NR2B and PKA signaling complexes organized by scaffolding proteins. We infused cell-permeable Tat peptides that displaced either NR2B from receptor for activated C kinase 1 (RACK1), or PKA from A-kinase anchor proteins (AKAPs) or microtubule-associated proteins (MAPs). The infusions were targeted to the retrosplenial cortex, an area involved in both fear extinction of remotely acquired memories and in mood regulation. Tat-RACK1 and Tat-AKAP enhanced fear extinction, all peptides reduced anxiety and none affected baseline depression-like behavior. However, disruption of PKA complexes distinctively interfered with the rapid antidepressant actions of the N-methyl-D-aspartate receptors antagonist MK-801 in that Tat-MAP2 blocked, whereas Tat-AKAP completely inverted the effect of MK-801 from antidepressant to depressant. These effects were unrelated to the MK-801-induced changes of brain-derived neurotrophic factor messenger RNA levels. Together, the findings suggest that NR2B-RACK1 complexes specifically contribute to fear extinction, and may provide a target for the treatment of PTSD. AKAP-PKA, on the other hand, appears to modulate fear extinction and antidepressant responses in opposite directions.
Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Maleato de Dizocilpina/farmacologia , Medo , Neuropeptídeos/metabolismo , Fragmentos de Peptídeos/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas de Ancoragem à Quinase A/metabolismo , Animais , Antidepressivos/farmacologia , Sintomas Comportamentais/tratamento farmacológico , Sintomas Comportamentais/metabolismo , Modelos Animais de Doenças , Extinção Psicológica/efeitos dos fármacos , Extinção Psicológica/fisiologia , Medo/efeitos dos fármacos , Medo/fisiologia , Hipocampo/metabolismo , Camundongos , Receptores de Quinase C Ativada , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Transtornos de Estresse Pós-Traumáticos/tratamento farmacológico , Transtornos de Estresse Pós-Traumáticos/metabolismoRESUMO
Corticotropin-releasing factor (CRF), urocortin, sauvagine and urotensin I form the CRF family. These peptides bind with different affinities to two subtypes of CRF receptor (CRFR), CRFR1 and CRFR2. The latter exists as two splice variants, the neuronal CRFR2a and the peripheral CRFR2b. CRFR is a G protein-dependent receptor which acts mainly through Gs enhancing cAMP production. However, CRFR1 expressed in neutrophils of the spleen in response to immunologic stimulation and psychological stress does not seem to function through Gs, as indicated by the inability of CRF to stimulate the cAMP production of CRFR1+ neutrophils. Besides the two receptors, a 37 kD CRF binding protein (CRF-BP) binds several CRF peptides with high affinity. CRFR and CRF-BP do not share a common amino acid sequence representing the ligand binding site. In view of the unusually slow offrate of CRF-BP, it is proposed that CRF-BP provides an efficient uptake of free extracellular CRF. Thus, the time of exposure of CRFR to CRF or urocortin can be limited. At this time, the fate of the ligand CRF-BP complex is unclear. CRFR1 is not only involved in the hypophyseal stimulation of corticotropin release, but hippocampal CRFR1 mediates enhancement of stress-induced learning. CRFR1 may also be involved in basic anxiety. In contrast, at least in the mouse, CRFR2 of the lateral intermediate septum mediates tonic impairment of learning. In response to stressful stimuli or after local injection of high CRF doses, CRFR2 mediates anxiety. Effects requiring CRFR2 can be blocked specifically by the recently developed peptidic antagonist antisauvagine-30.
Assuntos
Hormônio Liberador da Corticotropina/análogos & derivados , Hormônio Liberador da Corticotropina/farmacologia , Sequência de Aminoácidos , Animais , Hormônio Liberador da Corticotropina/química , Hormônio Liberador da Corticotropina/fisiologia , Humanos , Dados de Sequência Molecular , Receptores de Hormônio Liberador da Corticotropina/efeitos dos fármacos , Receptores de Hormônio Liberador da Corticotropina/metabolismoRESUMO
Corticotropin releasing factor (CRF) represents an early chemical signal in the stress response and modulates various brain functions through G protein-coupled receptors. Two CRF receptor subtypes, CRF(1) and CRF(2), have been identified. Since the physicochemical properties of CRF receptor antagonists might influence their biological potency, the peptidic antagonists astressin, alpha-helical CRF(9-41) (alpha-helCRF) and antisauvagine-30 (aSvg-30) have been analyzed. The rank order of solubility of these compounds in artificial cerebrospinal fluid (aCSF, pH 7.4) was aSvg-30>alpha-helCRF>>astressin, whereas the rank order of relative lipophilicity as determined with RP-HPLC was alpha-helCRF>astressin>aSvg-30. The calculated isoelectric points were 4.1 (alpha-helCRF), 7.4 (astressin) and 10.0 (aSvg-30). According to Schild analysis of the CRF receptor-dependent cAMP production of transfected HEK cells, aSvg-30 exhibited a competitive antagonism and displayed a 340 fold selectivity for mCRF(2 beta) receptor. For astressin, however, the pharmacodynamic profile could not be explained by a simple competitive mechanism as indicated by Schild slopes >1 for rCRF(1) or mCRF(2 beta) receptor. Behavioral experiments demonstrated that after i.c.v. injection, alpha-helCRF reduced oCRF-induced anxiety-like behavior in the elevated plus-maze, whereas astressin, despite its higher in vitro potency, did not. These findings could be explained by different physicochemical properties of the antagonists employed.
Assuntos
Comportamento Animal/efeitos dos fármacos , Hormônio Liberador da Corticotropina/farmacologia , Fármacos Neuroprotetores/farmacologia , Fragmentos de Peptídeos/farmacologia , Animais , Ansiedade/psicologia , Células Cultivadas , Cromatografia Líquida de Alta Pressão , Hormônio Liberador da Corticotropina/antagonistas & inibidores , Hormônio Liberador da Corticotropina/química , AMP Cíclico/metabolismo , Masculino , Membranas/efeitos dos fármacos , Membranas/metabolismo , Camundongos , Camundongos Endogâmicos BALB C , Neuropeptídeos/farmacologia , Fármacos Neuroprotetores/química , Fragmentos de Peptídeos/antagonistas & inibidores , Fragmentos de Peptídeos/química , Receptores de Hormônio Liberador da Corticotropina/antagonistas & inibidores , SolubilidadeRESUMO
We have demonstrated previously that stimulation of hippocampal corticotropin-releasing factor (CRF) receptors enhances, whereas stimulation of CRF receptors in the lateral intermediate septum impairs learning, as indicated by fear conditioning. Here, we report that the action of CRF within the hippocampus and lateral septum require muscarinic and D2 receptors, respectively.
Assuntos
Condicionamento Psicológico/fisiologia , Hormônio Liberador da Corticotropina/fisiologia , Medo/fisiologia , Receptores de Neurotransmissores/fisiologia , Animais , Benzazepinas/farmacologia , Hormônio Liberador da Corticotropina/farmacologia , Antagonistas de Dopamina/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Hipocampo , Humanos , Injeções , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Antagonistas Muscarínicos/farmacologia , Ácidos Pipecólicos/farmacologia , Ratos , Receptores de Dopamina D1/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Escopolamina/farmacologia , Septo PelúcidoRESUMO
Since the central nervous system and neuropeptides modulate immune functions, we investigated whether the different susceptibility of Lewis and Brown Norway rats to experimental allergic encephalomyelitis could also reflect differences in beta-endorphin and substance P concentrations in brain areas and macrophages during the development of the disease. We show that beta-endorphin concentrations increase much more in the hypothalamus and macrophages of Lewis rats during the development of the disease, while the increase is much lower or absent in Brown Norway rats. Tumor necrosis factor-alpha seems to play an important role in this difference. The administration of the opiate receptor antagonist naltrexone worsens the development of the disease, suggesting that the increase of the opioid beta-endorphin might represent a mechanism to downregulate the immune response. In both strains, the concentrations of substance P do not change.
Assuntos
Química Encefálica , Encefalomielite Autoimune Experimental/imunologia , Macrófagos Peritoneais/química , Fator de Necrose Tumoral alfa/metabolismo , beta-Endorfina/análise , Animais , Imunoglobulina G/sangue , Masculino , Naltrexona/farmacologia , Ratos , Ratos Endogâmicos BN , Ratos Endogâmicos Lew , Substância P/análise , Fator de Necrose Tumoral alfa/farmacologiaRESUMO
The effect of leucine-enkephalin (Leu-Enk) on primary humoral immune response was investigated following intracerebroventricular (i.c.v.) administration of the peptide in the rat. Leu-Enk stimulated plaque-forming cell (PFC) response in rats i.c.v. injected with 0.1 and 1 micrograms/kg, whereas does of 20 and 50 micrograms/kg exerted immunosuppressive effects. I.c.v. treatment of rats with delta opioid receptor antagonist ICI 174,864 and kappa opioid receptor antagonist nor-binaltorphimine (nor-BNI) blocked stimulation and suppression of PFC response induced by Leu-Enk, respectively. The mu opioid receptor antagonist beta-funaltrexamine (beta-FNA) reversed both immunomodulatory effects produced by Leu-Enk. Since beta-FNA alone had no effect on PFC response (unlike ICI 174,864 and nor-BNI), these data showed that central effects of Leu-Enk on PFC response were mediated by brain mu opioid receptors, and suggested a possible involvement of delta and kappa opioid receptors.
Assuntos
Formação de Anticorpos/efeitos dos fármacos , Encéfalo/fisiologia , Encefalina Leucina/farmacologia , Receptores Opioides delta/antagonistas & inibidores , Receptores Opioides kappa/antagonistas & inibidores , Receptores Opioides mu/antagonistas & inibidores , Adjuvantes Imunológicos/farmacologia , Animais , Células Produtoras de Anticorpos/efeitos dos fármacos , Relação Dose-Resposta a Droga , Encefalina Leucina/análogos & derivados , Técnica de Placa Hemolítica , Injeções Intraventriculares , Masculino , Naltrexona/análogos & derivados , Naltrexona/farmacologia , Ratos , Ratos WistarRESUMO
The selective kappa opioid receptor agonist MR 2034 exerted pronounced suppression of plaque-forming cell (PFC) response following intraperitoneal (i.p.) administration in the rat. Pretreatment with preferential kappa and mu opioid receptor antagonists MR 2266 and naloxone, respectively, revealed that this effect was mediated mainly by kappa, and to a low extent by mu opioid receptors. Intracerebroventricular (i.c.v.) administration of quaternary naltrexone (QNtx) moderately attenuated, whereas i.p. given QNtx completely prevented the suppressive effect of MR 2034, suggesting a peripheral mechanism of action, and only minor involvement of brain opioid receptors. MR 2034 markedly decreased the PFC response of spleen cells obtained from in vivo immunized rats, treated in vitro with the opiate. The immunosuppressive action of MR 2034 in vitro was completely and partially blocked by equimolar concentrations of MR 2266 and naloxone, respectively. Antagonists alone produced stimulation of PFC following i.p. administration in the rat, but did not affect PFC response upon in vitro treatment. These results suggest that peripheral kappa opioid receptors down-regulate primary humoral immune response in the rat, and that this effect may be produced by direct interference with plasma cell activity.
Assuntos
Tolerância Imunológica , Receptores Opioides kappa/fisiologia , Animais , Formação de Anticorpos/efeitos dos fármacos , Benzomorfanos/farmacologia , Imunossupressores/farmacologia , Masculino , Naloxona/farmacologia , Ratos , Ratos Wistar , OvinosRESUMO
The proliferative response of human or rat T lymphocytes to phytohemagglutinin (PHA) or concanavalin A (ConA) was measured after acute (30 min) or chronic (8 days) treatment with the opiate receptor antagonists naloxone or naltrexone. Both in the rat and in the human, proliferation was significantly enhanced by acute treatment with the opiate receptor antagonists. In contrast, after chronic treatment proliferation always decreased. The sudden removal of an opioid inhibitory tone might be the basis for the increased proliferative responses observed after acute treatment. The decrease after chronic treatment could be ascribed to the amplification of the inhibitory effect of endogenous opioids due to the up-regulation of opiate receptors that follows chronic antagonist administration. Receptor binding studies of beta-endorphin receptors on splenocytes of chronically naloxone treated rats confirmed this hypothesis: a higher number of beta-endorphin receptors were expressed on splenocytes of naloxone-treated rats compared to controls (Bmax = 9.8 x 10(-12) vs. 1.16 x 10(-12), respectively).
Assuntos
Entorpecentes/farmacologia , Linfócitos T/efeitos dos fármacos , Adulto , Animais , Divisão Celular/efeitos dos fármacos , Concanavalina A/farmacologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Naloxona/farmacologia , Naltrexona/farmacologia , Fito-Hemaglutininas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores Opioides/metabolismo , Linfócitos T/citologia , beta-Endorfina/metabolismoRESUMO
Phosphorylation of the cAMP response element binding protein (pCREB) triggered by associative learning was monitored immunohistochemically in different areas of the mouse brain during a 6-h interval, starting immediately after training. One trial context-dependent fear conditioning was employed as a learning paradigm. Training consisted of contextual exposure followed by shock. Control groups consisted of naïve mice, mice exposed to the context alone and mice exposed to an immediate shock in the context. For all trained mice, the time course of CREB phosphorylation in hippocampus, parietal cortex and amygdaloid nuclei exhibited a biphasic pattern. The early phase was between 0 and 30 min, and the late phase was between 3 and 6 h after training. The animals exposed to context followed by an electric shock, as well as those exposed to an immediate electric shock, exhibited significantly higher pCREB levels than the mice subjected to context alone. During the late phase, the pCREB levels were highest in the mice exposed to the context followed by shock. It was observed that CREB phosphorylation and Fos production followed different regional and stimulus-dependent patterns. It is suggested that the early phase of pCREB increase may be related to stress-related behaviors, whereas the late phase may rather relate to memory consolidation.
Assuntos
Química Encefálica/fisiologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Medo/fisiologia , Proteínas Proto-Oncogênicas c-fos/biossíntese , Tonsila do Cerebelo/fisiologia , Animais , Aprendizagem por Associação/fisiologia , Condicionamento Psicológico/fisiologia , Giro Denteado/fisiologia , Eletroconvulsoterapia , Masculino , Memória/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Lobo Parietal/fisiologia , Fosforilação , Proteínas Proto-Oncogênicas c-fos/análiseRESUMO
Glutamatergic and dopaminergic effects on molecular processes have been extensively investigated in the basal ganglia. It has been demonstrated that NMDA and dopamine D(1) and D(2) receptors interact in the regulation of signal transduction and induction of transcription factors. In the present experiments, NMDA/dopamine interactions were investigated in the normosensitive caudate nucleus, hippocampus and amygdala by monitoring Fos production. We demonstrated that NMDA and the D(1) receptor agonist SKF 38393 triggered Fos levels in a distinct, non-overlapping and region-specific pattern. NMDA injected intraperitoneally (i.p.) elevated Fos levels in all hippocampal subfields and the central amygdala, whereas SKF 38393 triggered Fos production in basomedial, cortical, medial amygdala and caudate nucleus. The NMDA receptor antagonist CGS 19755 prevented NMDA- and SKF 38393-triggered Fos production in all investigated brain areas. Similarly, the D(1) receptor antagonist SCH 23390 inhibited the effects produced by SKF 38393 or NMDA. The D(2) receptor antagonist sulpiride exerted synergistic and antagonistic effects on NMDA- and SKF 38393-triggered Fos production, in a region specific manner. These data suggest that NMDA and dopamine receptors regulate Fos production within the limbic system and basal ganglia through regionally differentiated but interdependent actions.
Assuntos
Gânglios da Base/metabolismo , Dopamina/metabolismo , Sistema Límbico/metabolismo , N-Metilaspartato/metabolismo , Proteínas Oncogênicas v-fos/biossíntese , Animais , Gânglios da Base/química , Núcleo Caudado/metabolismo , Hipocampo/metabolismo , Imuno-Histoquímica , Sistema Límbico/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Receptores de N-Metil-D-Aspartato/metabolismoRESUMO
The significance of different domains of corticotropin-releasing factor receptor, type 1, (CRFR1) for ligand binding and cAMP accumulation was investigated with C-terminally truncated forms of rat CRFR1 (rCRFR1) tagged by a sequence of six histidine residues (His-tag) to facilitate protein purification and identification. These different forms of the receptor were N-glycosylated and transported properly to the membranes of transfected mammalian cells as indicated by Western blot analysis and immunocytochemical staining with two polyclonal antibodies developed against the N- and C-terminus of rCRFR1. The N-terminal fragment, rCRFR1(23-121), expressed in Escherichia coli bound oCRF specifically, but with low affinity. Several mutants lacking transmembrane domain (TM) 7 and the C-terminus exhibited similarly low affinities to oCRF after expression in transfected mammalian cells. None of these cells produced significant amounts of cAMP after exposure to oCRF. Only mutants containing the N-terminus, all loops and TMs bound oCRF and produced cAMP with high affinity (Kd = 62 nM) and efficacy (EC50 = 0.8 nM). The additional presence of the C-terminus provided similar characteristics (Kd = 5 nM, EC50 = 0.3 nM) as known for the native receptor. It is suggested on the basis of these data that the last extracellular loop is involved in ligand binding.
Assuntos
Receptores de Hormônio Liberador da Corticotropina/química , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Sequência de Aminoácidos , Animais , Células CHO , Linhagem Celular , Membrana Celular/metabolismo , Hormônio Liberador da Corticotropina/metabolismo , Cricetinae , Humanos , Cinética , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Fragmentos de Peptídeos/química , Estrutura Secundária de Proteína , Ensaio Radioligante , Ratos , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Deleção de Sequência , Relação Estrutura-Atividade , TransfecçãoRESUMO
A 1-trial fear conditioning was used to investigate the temporal development of fear responses expressed as increase of freezing or heart rate and its impairment by the protein synthesis inhibitor cycloheximide (CHX) in male C57BL/6N mice. Heart rate was measured with an implanted transmitter. In the memory tests, mice were exposed to tone and context provided either as foreground or background stimulus during training. The fear responses developed differently from 0 to 24 hr after training under these 3 conditions. A single pretraining CHX injection impaired both memory forms, whereas a single posttraining CHX injection impaired tone- but not context-dependent memory, with the context provided as background stimulus. It was concluded that consolidation of tone-, foreground context-, and background context-dependent fear conditioning may be mediated by partly different neuronal or partly different biochemical pathways, or both.
Assuntos
Estimulação Acústica , Condicionamento Operante/efeitos dos fármacos , Cicloeximida/efeitos adversos , Eletrochoque , Medo , Memória/efeitos dos fármacos , Inibidores da Síntese de Proteínas/efeitos adversos , Animais , Cicloeximida/administração & dosagem , Relação Dose-Resposta a Droga , Eletrocardiografia , Frequência Cardíaca , Imobilização , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Inibidores da Síntese de Proteínas/administração & dosagem , Fatores de TempoRESUMO
Neuropeptide Y (NPY) and endogenous opioids (EOPs) such as methionine-enkephalin (Met-enk) regulate similar physiological responses, but it is not known whether nociceptive and immune responses also show analogy after intracerebroventricular (i.c.v.) application. Dose-response studies show that Met-enk stimulates the blood granulocyte and splenic natural killer (NK) cell function of Lewis rats at a low dose (10(2) ng/kg, i.c.v.), whereas a high dose (10(5) ng/kg) causes suppression of innate immune functions associated with analgesia in the hot-plate test. At 15 min, 1 h and 24 h after i.c.v. application, both Met-enk (10(2) ng/kg) and NPY (1 ng/kg) produced similar effects: An initial suppression of innate immune function was followed by a long lasting stimulatory action on cell functions and serum interleukin-6 (sIL-6) levels. Thus, central NPY application resembles Met-enk-induced immunostimulation at doses not affecting nociception, suggesting an involvement of both peptides in shaping stress-induced immunomodulation of the non-analgetic form, possibly via activation of a common immunomodulatory effector mechanism.
Assuntos
Adjuvantes Imunológicos/farmacologia , Encefalina Metionina/farmacologia , Neuropeptídeo Y/farmacologia , Analgésicos/farmacologia , Animais , Relação Dose-Resposta a Droga , Injeções Intraventriculares , Masculino , Dor/fisiopatologia , Ratos , Ratos Endogâmicos LewRESUMO
Effects of Met-enkephalin (Met-ENK) and opioid antagonists on H2O2 release by peritoneal macrophages from DA and AO rats were investigated. Met-ENK increased and decreased H2O2 production by macrophages of DA and AO rats, respectively. These effects were antagonized by low, but not high, concentrations of naloxone and ICI 174864. High concentrations of both antagonists directly modulated H2O2 release and retained the strain-related differences seen with Met-ENK. The results showed direct, strain- and dose-dependent, effects of Met-ENK, naloxone, and ICI 174864 on rat macrophage function.
Assuntos
Encefalina Metionina/farmacologia , Peróxido de Hidrogênio/metabolismo , Macrófagos/efeitos dos fármacos , Antagonistas de Entorpecentes/farmacologia , Acetato de Tetradecanoilforbol/farmacologia , Animais , Relação Dose-Resposta a Droga , Encefalina Leucina/análogos & derivados , Encefalina Leucina/farmacologia , Humanos , Recém-Nascido , Masculino , Naloxona/farmacologia , Ratos , Ratos EndogâmicosRESUMO
This work demonstrates technical approaches to high-quality magnetic resonance imaging (MRI) of small structures of the mouse brain in vivo. It turns out that excellent soft-tissue contrast requires the reduction of partial volume effects by using 3D MRI at high (isotropic) resolution with linear voxel dimensions of about 100-150 microm. The long T(2)* relaxation times at relatively low magnetic fields (2.35 T) offer the benefit of a small receiver bandwidth (increased signal-to-noise) at a moderate echo time which together with the small voxel size avoids visual susceptibility artifacts. For measuring times of 1-1.5 h both T(1)-weighted (FLASH) and T(2)-weighted (Fast Spin-Echo) 3D MRI acquisitions exhibit detailed anatomical insights in accordance with histological sections from a mouse brain atlas. Preliminary applications address the identification of neuroanatomical variations in different mouse strains and the use of Mn(2+) as a T(1) contrast agent for neuroaxonal tracing of fiber tracts within the mouse visual pathway.