RESUMO
Sex-biased differences in schizophrenia are evident in several features of the disease, including symptomatology and response to pharmacological treatments. As a neurodevelopmental disorder, these differences might originate early in life and emerge later during adolescence. Considering that the disruption of the glutamatergic system during development is known to contribute to schizophrenia, we hypothesized that the neonatal phencyclidine model could induce sex-dependent behavioral and neurochemical changes associated with this disorder during adolescence. C57BL/6 mice received either saline or phencyclidine (5, 10, or 20 mg/kg) on postnatal days (PN) 7, 9, and 11. Behavioral assessment occurred in late adolescence (PN48-50), when mice were submitted to the open field, social interaction, and prepulse inhibition tests. Either olanzapine or saline was administered before each test. The NMDAR obligatory GluN1 subunit and the postsynaptic density protein 95 (PSD-95) were evaluated in the frontal cortex and hippocampus at early (PN30) and late (PN50) adolescence. Neonatal phencyclidine evoked dose-dependent deficits in all analyzed behaviors and males were more susceptible. Males also had reduced GluN1 expression in the frontal cortex at PN30. There were late-emergent effects at PN50. Cortical GluN1 was increased in both sexes, while phencyclidine increased cortical and decreased hippocampal PSD-95 in females. Olanzapine failed to mitigate most phencyclidine-evoked alterations. In some instances, this antipsychotic aggravated the deficits or potentiated subthreshold effects. These results lend support to the use of neonatal phencyclidine as a sex-biased neurodevelopmental preclinical model of schizophrenia. Olanzapine null effects and deleterious outcomes suggest that its use during adolescence should be further evaluated.
Assuntos
Antipsicóticos , Esquizofrenia , Masculino , Feminino , Animais , Camundongos , Fenciclidina/farmacologia , Esquizofrenia/induzido quimicamente , Esquizofrenia/tratamento farmacológico , Olanzapina/uso terapêutico , Camundongos Endogâmicos C57BL , Antipsicóticos/farmacologia , Antipsicóticos/uso terapêutico , Modelos Animais de DoençasRESUMO
BACKGROUND: N-methyl-d-aspartate receptor (NMDAR) dysfunction is implicated in schizophrenia, and NMDAR antagonists, such as phencyclidine (PCP), can induce behaviours that mimic aspects of the disorder. AIMS: We investigated DNA methylation of Grin1, Grin2a and Grin2b promoter region and NR1 and NR2 protein expression in the prefrontal cortex (PFC) and hippocampus of adult female Lister-hooded rats following subchronic PCP (scPCP) administration. We also determined whether any alterations were tissue-specific. METHODS: Rats were divided into two groups that received vehicle (0.9% saline) or 2 mg/kg PCP twice a day for 7 days (n = 10 per group). After behavioural testing (novel object recognition), to confirm a cognitive deficit, brains were dissected and NMDAR subunit DNA methylation and protein expression were analysed by pyrosequencing and ELISA. Line-1 methylation was determined as a measure of global methylation. Data were analysed using Student's t-test and Pearson correlation. RESULTS: The scPCP administration led to Grin1 and Grin2b hypermethylation and reduction in NR1 protein in both PFC and hippocampus. No significant differences were observed in Line-1 or Grin2a methylation and NR2 protein. CONCLUSIONS: The scPCP treatment resulted in increased DNA methylation at promoter sites of Grin1 and Grin2b NMDAR subunits in two brain areas implicated in schizophrenia, independent of any global change in DNA methylation, and are similar to our observations in a neurodevelopmental animal model of schizophrenia - social isolation rearing post-weaning. Moreover, these alterations may contribute to the changes in protein expression for NMDAR subunits demonstrating the potential importance of epigenetic mechanisms in schizophrenia.
Assuntos
Metilação de DNA/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Fenciclidina/farmacologia , Receptores de N-Metil-D-Aspartato/genética , Animais , Comportamento Animal/efeitos dos fármacos , Disfunção Cognitiva/genética , Disfunção Cognitiva/fisiopatologia , Modelos Animais de Doenças , Epigênese Genética , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Feminino , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Fenciclidina/administração & dosagem , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , RatosRESUMO
Mephedrone and methedrone are cathinone-related compounds, which act as non-selective substrates for monoamine transporters, facilitating a neurotransmitter release. We compared the acute pharmacological effects of mephedrone and methedrone, attempting to further evaluate the action mechanisms of methedrone by responsibly and ethically using mice under approved procedures. The effects of both compounds were examined from 10 to 60 min, in a series of behavioral paradigms, namely open-field, plus-maze, hot-plate and tail suspension tests, whereas neurotransmitter brain tissue levels were determined ex vivo by HPLC. Separate groups were pre-treated with the dopamine (DA) antagonist haloperidol, or the serotonin (5-HT) synthesis inhibitor ρCPA, to further assess the mechanisms underlying methedrone effects. The compounds caused marked hyperlocomotion, displaying dissimilar stereotyped behavior, in an open-field arena. Mephedrone caused anxiolytic-like effects, while methedrone induced anxiogenic-like actions in the elevated plus-maze. Both compounds displayed thermal antinociception, with a reduced immobility time in the tail suspension model. Mephedrone triggered a 2- and 3-fold increment of dopamine and serotonin tissue levels, respectively, in the nucleus accumbens, with a 1.5-fold elevation of tissue dopamine in the frontal cortex. Methedrone caused a 2-fold increment of tissue dopamine in the nucleus accumbens and in the striatum, and a 1.5-fold increment of serotonin tissue levels in the hippocampus and striatum. In vivo methedrone effects were partially inhibited by a pre-treatment with haloperidol or ρCPA. Despite similar actions on locomotion, analgesia, and depression-like behavior, the acute administration of mephedrone and methedrone elicited divergent effects on anxiety-like behavior and stereotyped movements in mice, which might be related to the distinct modulation of brain tissue neurotransmitter levels.
Assuntos
Ansiolíticos/farmacologia , Encéfalo/efeitos dos fármacos , Metanfetamina/análogos & derivados , Propiofenonas/farmacologia , Animais , Temperatura Corporal/efeitos dos fármacos , Encéfalo/metabolismo , Relação Dose-Resposta a Droga , Comportamento Exploratório/efeitos dos fármacos , Feminino , Alucinógenos/farmacologia , Haloperidol/farmacologia , Elevação dos Membros Posteriores , Locomoção/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos dos fármacos , Metanfetamina/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Neurotransmissores/metabolismo , Medição da Dor/efeitos dos fármacos , Fenciclidina/farmacologia , Comportamento Estereotipado/efeitos dos fármacosRESUMO
A pesar de los avances en el conocimiento de las bases biológicas de la conducta, los mecanismos neurobiológicos precisos involucrados en la esquizofrenia permanecen desconocidos. Como consecuencia de esto las terapias farmacológicas actuales descansan más sobre bases empíricas que sobre explicaciones fisiopatológicas. En el presente trabajo se propone un modelo de la esquizofrenia que podría ser de utilidad en el diseño de nuevas estrategias terapéuticas. Este modelo intenta integrar recientes hallazgos neuropsicológicos y de neuroimagen con lo que hoy sabemos respecto a la biología del desarrollo y plasticidad cerebral normal. Se propone que la esquizofrenia es una enfermedad del neurodesarrollo caracterizada por una neurotransmisión glutamatérgica inadecuadamente modulada a consecuencia de la disfunción de interneuronas GABAérgicas en múltiples regiones del cerebro. Anormalidades sutiles en el balance entre GABA y Glutamato explicarían los defectos en la cognición, la conducta social y la coordinación motora reportados en las etapas pre-psicóticas de la esquizofrenia. Más tarde en la historia natural de la enfermedad, estados hiperglutamatérgicos desencadenados por la incrementada neurotransmisión dopaminérgica propia de la peri-adolescencia y adultez temprana llevarían a la psicosis. Esta excesiva actividad glutamatérgica conduciría a su vez a las reducciones progresivas en sustancia gris y blanca observadas en recientes estudios prospectivos. En apoyo a esta hipótesis, se describen estudios propios y de otros laboratorios con pacientes esquizofrénicos, así como en un modelo animal de exposición intermitente a fenciclidina. Como corolario, drogas moduladoras de la neurotransmisión glutamatérgica, tales como acamprosato y lamotrigina, son propuestas como estrategias terapéuticas potencialmente utilizables en las etapas tempranas de la esquizofrenia.
Assuntos
Animais , Humanos , Esquizofrenia/genética , Esquizofrenia/metabolismo , Ácido Glutâmico/metabolismo , Ácido gama-Aminobutírico/metabolismo , Antipsicóticos/uso terapêutico , Modelos Animais de Doenças , Dopamina/metabolismo , Esquizofrenia/fisiopatologia , Esquizofrenia/tratamento farmacológico , Fenciclidina/farmacologia , Neurotransmissores , Psicoses Induzidas por Substâncias , Receptores de N-Metil-D-Aspartato/antagonistas & inibidoresRESUMO
In addition to their well known actions on monoamine reuptake, tricyclic antidepressants have been shown to modulate ligand-gated ion channels (LGICs). Since the muscle nicotinic acetylcholine receptor (AChR) has been the model for studying structure-function relationships of LGICs, we analyzed the action of tricyclic antidepressants on this type of AChR at both single-channel and macroscopic current levels. We also determined their effects on ACh equilibrium binding and their interactions with the different conformational states of the AChR. Antidepressants produce a significant concentration-dependent decrease in the duration of clusters of single-channels (eight fold at 20 muM). They also decrease the peak amplitude and increase the decay rate of currents elicited by rapid perfusion of ACh to outside-out patches. In equilibrium binding assays, antidepressants promote the typical high-affinity desensitized state and inhibit binding of [piperidyl-3,4-(3)H (N)]-(N-(1-(2-thienyl)cyclohexyl)-3,4-piperidine ([(3)H]TCP) to its locus in resting and desensitized AChRs. The results indicate that tricyclic antidepressants: (i) interact with resting (closed), open, and desensitized channels; (ii) do not affect significantly channel opening and closing rates; (iii) do not act as fast open-channel blockers; (iv) inhibit activation of resting channels; and (v) may increase the rate of long-lived desensitization from the open state.
Assuntos
Antidepressivos Tricíclicos/farmacologia , Antagonistas Nicotínicos/farmacologia , Fenciclidina/análogos & derivados , Receptores Nicotínicos/efeitos dos fármacos , Acetilcolina/metabolismo , Amitriptilina/farmacologia , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Doxepina/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Humanos , Imipramina/farmacologia , Técnicas In Vitro , Rim/citologia , Rim/efeitos dos fármacos , Rim/metabolismo , Cinética , Potenciais da Membrana/efeitos dos fármacos , Camundongos , Técnicas de Patch-Clamp , Fenciclidina/farmacologia , Receptores Nicotínicos/metabolismo , TorpedoRESUMO
Phencyclidine (PCP) is a non-competitive inhibitor of the nicotinic acetylcholine receptor (nAChR) with biphasic characteristics. At low and high micromolar concentrations, PCP inhibits nAChR from fetal mouse muscle, whereas at intermediate concentrations PCP does not inhibit the receptor. The present study was performed to determine whether the high and low concentration effects of PCP on mouse nAChR were due to interactions of this blocker with channel lining amino acids. In order to test this hypothesis, we examined the ability of PCP to inhibit acetylcholine-induced currents from wild-type nAChR and nAChR in which amino acid substitutions were made in the 6', 8' and 10' positions of the M2 transmembrane segments of the receptor. Fetal mouse nAChR from BC(3)H-1 cells were expressed in Xenopus laevis oocytes and studied using the two-electrode voltage clamp technique. The results of this study reveal that in native fetal muscle receptor, PCP potency is not affected by membrane potential between -80 mV and -30 mV. The potency of PCP is increased by mutations in M2 6', 8', and 10' positions. This increase in potency cannot be explained merely by either changes in hydrophobicity/hydrophilicity of amino acids at these positions or by side-chain size. A model proposing extra-luminal inhibitory and regulatory sites for PCP explains the lack of voltage-dependency, the biphasic effect of PCP, and the fact that all M2 mutations increased PCP potency (by disrupting the link with the regulatory sites).
Assuntos
Antagonistas de Aminoácidos Excitatórios/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Ativação do Canal Iônico/genética , Fenciclidina/farmacologia , Receptores Nicotínicos/genética , Acetilcolina/farmacologia , Sequência de Aminoácidos , Animais , Linhagem Celular , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Dados de Sequência Molecular , Mutagênese/fisiologia , Oócitos/fisiologia , Técnicas de Patch-Clamp , Vasodilatadores/farmacologia , Xenopus laevisRESUMO
Este experimento teve por objetivo avaliar a viabilidade do emprego da levomepromazina no bloqueio da atividade arritmogênica da adrenalina, em cäes anestesiados pela quetamina. Para tal, foram utilizados 30 cäes adultos, machos e fêmeas, considerados sadios, com pesos compreendidos entre 7 e 14kg. Estes foram divididos em 3 grupos de 10 animais (G1, G2 e G3). Aos cäes de G1 foi administrada, por via intravenosa, adrenalina em doses de 3, 6, 9, 12 e 15µg/kg, em intervalos de 10 minutos. Deste grupo, foram colhidos o tempo de duraçäo do efeito da catecolamina (TA), estabelecido pela contagem da freqüência cardíaca e o número total de batimentos cardíacos de origem ectópica, produzidos pela adrenalina (ESV). Aos animais do G2, foi administrada soluçäo salina a 0,9 porcento, na dose de 0,2ml/kg, por via intravenosa, seguida, 10 minutos após, da injeçäo, pela mesma via, de quetamina, na dose de 2mg/kg. Decorridos 5 minutos, iniciou-se a infusäo contínua de quetamina, por via intravenosa, na dose de 0,2mg/kg/min. Aguardou-se 5 minutos e iniciou-se a adminstraçäo de adrenalina e colheita das variáveis, conforme protocolado para o G1. Aos animais do G3, aplicou-se a mesma metodologia, substituindo-se o placebo pela levomepromazina, administrada por via intravenosa, na dose de 1mg/kg. A análise dos resultados mostrou que a levomepromazina reduz a duraçäo do efeito da catecolamina e minimiza o aparecimento de batimentos cardíacos de origem ectópica. Os achados permitiram concluir que a levomepromazina é útil no bloqueio da arritmia produzida pela adrenalina em cäes anestesiados pela quetamina.
Assuntos
Animais , Masculino , Feminino , Cães , Antipsicóticos/farmacologia , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/veterinária , Coração , Epinefrina/efeitos adversos , Inibidores Enzimáticos/farmacologia , Metotrimeprazina/farmacologia , Fenciclidina/farmacologia , Vasoconstritores/efeitos adversos , Anestesia/veterináriaRESUMO
The present study examined the effects of 0.1% dimethyl sulfoxide (DMSO) on nicotinic acetylcholine receptors (nAChR) from mouse muscle and Torpedo californica electrocytes. Receptors were expressed in Xenopus laevis oocytes and studied with voltage-clamp. When applied simultaneously with acetylcholine, DMSO did not inhibit current amplitude of either receptor. Preincubation with DMSO for 1 min reduced current amplitude by approximately 50% from oocytes expressing electrocyte receptor. Preincubation did not affect the muscle receptor. With electric organ membranes, 0.1% DMSO did not block either [alpha-(125)I]bungarotoxin binding to the nAChR agonist site or [3H]phencyclidine binding to its high affinity site on resting or desensitized receptor. These data suggest that DMSO might be affecting the electrocyte receptor through a second messenger system.
Assuntos
Anti-Inflamatórios/farmacologia , Dimetil Sulfóxido/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Receptores Nicotínicos/fisiologia , Administração Tópica , Animais , Bungarotoxinas/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Radioisótopos do Iodo , Camundongos , Oócitos/química , Oócitos/fisiologia , Técnicas de Patch-Clamp , Fenciclidina/farmacologia , Ensaio Radioligante , Torpedo , Trítio , Xenopus laevisRESUMO
The propionyl-CoA condensing enzyme which catalyzes the first step in the biosynthesis of 2-methylbutyrate and 2-methylvalerate by Ascaris muscle appears to exist in at least three forms in the mitochondria of this parasitic nematode. Two forms, A and B, were separated by ion exchange chromatography on CM-Sephadex. Chromatography on phosphocellulose resulted in the recovery of one minor peak (I) and two major peaks with activity (II and III). A and B as well as I, II, and III differed in their specific activities. Forms B and III were the most retained by their resins, and were the most active forms of the enzyme in each case. Inhibition studies with metabolites from Ascaris mitochondria indicate that CoASH, a product of the condensation reaction, and acetyl-CoA are effective inhibitors of the condensing and thiolytic activities of the Ascaris enzyme, respectively. Incubation of the active enzyme form B for 2 h with 0.1 mM CoASH at room temperature under nitrogen caused the loss of 92% of the propionyl-CoA condensing activity and 67% of the thiolase activity when assayed in standard mixtures. The propionyl-CoA condensing enzyme exhibited a hyperbolic dependence of the condensation velocity to changes in substrate concentration. However, in the presence of CoASH the Michaelis-Menten kinetics was transformed into a sigmoidal kinetics indicating a deviation from a simple product inhibition. Inactivation of the most active forms of the enzyme with CoASH was accompanied by (a) a change in the chemical reactivity of the protein toward p-chloromurcuribenzoate, (b) a change in the uv-visible spectrum of the protein, and (c) a change in the elution patterns from both CM-Sephadex and phosphocellulose column chromatography, where-upon one, two, or more protein peaks were obtained. The several protein peaks resolved by rechromatography of the [14C]CoASH-inactivated enzyme III on phosphocellulose had different CoASH contents. The elution positions were correlated with the less active forms (I and II) having increased [14C]CoASH activities. Similarly, the two peaks isolated upon rechromatography of the CoASH-partially inactivated enzyme B on CM-Sephadex had different isotope contents and the elution position of enzyme A corresponded to the less active form. The results described indicate that the CoASH modification of Ascaris propionyl-CoA condensing enzyme may be responsible for the existence of several forms of the enzyme and might represent a mode of control by chemically modulating the amount of the active forms of the enzyme.
Assuntos
Oxirredutases do Álcool/metabolismo , Ascaris/enzimologia , Mitocôndrias Musculares/enzimologia , Acetil-CoA C-Acetiltransferase/metabolismo , Animais , Ascaris/efeitos dos fármacos , Coenzima A/farmacologia , Ativação Enzimática/efeitos dos fármacos , Isoenzimas/metabolismo , Cinética , Mitocôndrias Musculares/efeitos dos fármacos , Nitrogênio/farmacologia , Fenciclidina/análogos & derivados , Fenciclidina/farmacologiaRESUMO
The effect of vesicular acetylcholine (ACh) transport blocker 2-(4-phenylpiperidino)cyclohexanol (AH-5183) on the subcellular storage and release of ACh was studied in rat brain cortical slices. AH-5183 reduced the release of ACh from cortical slices stimulated by tityustoxin and ouabain. Tissue stimulated in the presence of AH-5183 contained more ACh in both the nerve terminal synaptic vesicles and cytoplasmic fraction than did tissue stimulated in drug's absence. Thus, AH-5183 blocked the tityustoxin and ouabain induced release of ACh from both cytoplasmic and vesicular pools. AH-5183 also depressed the spontaneous release of ACh from incubated slices and, in this condition, the drug had no effect in the subcellular distribution of ACh. It is suggested that AH-5183 interferes with the process of ACh release independent of its blocking action on ACh transport into the synaptic vesicles.