RESUMO
Non-competitive NMDA-receptor-antagonist drugs such as dizocilpine (MK801) induce behavioral changes and neurotoxicity that have made an impact in different fields of neuroscience. New approaches in research use transgenic mice to elucidate cellular mechanisms and circuits involved in the effects of these drugs. However, the neurodegeneration induced by these drugs has been extensively studied in rats, but the data in mice is limited. Therefore it is important to characterize if the neurotoxic pattern in mice corresponds to that of rats. A comparative analysis of the neurodegeneration induced by MK801 (10mg/kg) between Wistar rats, and CD-1, CF-1, and C57BL/6-129/Sv mice of both sexes, at different survival times (15, 24, 32, 48, 56 and 72 h) was analysed with the amino-cupric-silver and fluoro-jade B techniques. To compare different administration patterns, groups of mice received subchronic treatments with different doses (final doses of 20 and 40 mg/kg). Results showed that mice treated with MK801 presented different neurotoxic profiles, such as excitotoxic-like cell death in the retrosplenial cortex, terminal degeneration in CA1 and apoptotic-like degeneration in the olfactory bulb. Unlike rats, mice subjected to the same treatment failed to show neurodegeneration in corticolimbic areas such as piriform cortex and dentate gyrus. The amount of degeneration was lower in mice, and the subchronic administration of MK801 did not change the neurotoxic pattern. Additionally, mice lacked the sexually dimorphic response to MK801 toxicity observed in rats. Altogether these results indicate important species dissimilarities. Neurotoxicological studies aimed to explore pathways and mechanisms of MK801 toxicity should consider these differences when using mice as rodent models.
Assuntos
Maleato de Dizocilpina/toxicidade , Antagonistas de Aminoácidos Excitatórios/toxicidade , Doenças Neurodegenerativas/induzido quimicamente , Análise de Variância , Animais , Comportamento Animal , Modelos Animais de Doenças , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Doenças Neurodegenerativas/patologia , Doenças Neurodegenerativas/fisiopatologia , Neurônios/patologia , Ratos , Ratos Wistar , Fatores Sexuais , Fatores de TempoRESUMO
MK801, PCP, and ketamine are non-competitive NMDA receptor-antagonists drugs that in humans produce psychomimetic effects and neurocognitive disturbances reminiscent to those of schizophrenia. The administration of these drugs in animals has been used as a pharmacological model to study the NMDA receptor hypofunction-hypothesis of schizophrenia. In animals, the biological effect of MK801 is dose-dependent. Low doses induce behavioral disturbances and higher doses, in addition, promote neurotoxicity in many brain regions, particularly the granular retrosplenial cortex (RSG). The neurotoxic effect of MK801 is sexually dimorphic, being females markedly more sensitive than males; however, the involvement of gonadal hormones is elusive. Here we show that a single intraperitoneal injection of 5 mg/kg of MK801 induced overt neurodegeneration in RSG of female rats, including abundant somatic degeneration in layer 4, and somatodendritic and terminal degeneration in layers 1, 4, and 5. MK801-degeneration in males was scarce and mainly evidenced by the presence of few argirophilic somas in layer 4. Ovariectomized rats were not significantly different than intact females, while orchiectomized rats showed robust MK801-toxicity. Testosterone and dihydrotestosterone (DHT) inhibit MK801-toxicity in orchiectomized rats. In ovariectomized rats only DHT, but not testosterone, prevented MK801-induced degeneration, while in intact females, DHT was only partially protective. Treatment of intact males with estradiol benzoate significantly enhanced MK801-toxicity. Altogether, our experiments indicate that non-aromatizable androgens protect RSG from MK801-toxicity, while estrogens counteract this protection. Thus, the balance of androgens and estrogens delineate the sexual dimorphism of the RSG to the toxic effect of MK801.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Maleato de Dizocilpina/toxicidade , Hormônios Gonadais/farmacologia , Degeneração Neural/prevenção & controle , Neurônios/efeitos dos fármacos , Androgênios/administração & dosagem , Androgênios/farmacologia , Animais , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/patologia , Anticoncepcionais/administração & dosagem , Anticoncepcionais/farmacologia , Di-Hidrotestosterona/administração & dosagem , Di-Hidrotestosterona/farmacologia , Maleato de Dizocilpina/administração & dosagem , Estradiol/administração & dosagem , Estradiol/análogos & derivados , Estradiol/farmacologia , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Antagonistas de Aminoácidos Excitatórios/toxicidade , Feminino , Hormônios Gonadais/administração & dosagem , Injeções Intraperitoneais , Injeções Subcutâneas , Masculino , Degeneração Neural/induzido quimicamente , Neurônios/patologia , Orquiectomia , Ovariectomia , Ratos , Ratos Wistar , Fatores Sexuais , Propionato de Testosterona/administração & dosagem , Propionato de Testosterona/farmacologiaRESUMO
Deposition of fibrillar amyloid beta (fAbeta) plays a critical role in Alzheimer's disease (AD). We have shown recently that fAbeta-induced dystrophy requires the activation of focal adhesion proteins and the formation of aberrant focal adhesion structures, suggesting the activation of a mechanism of maladaptative plasticity in AD. Focal adhesions are actin-based structures that provide a structural link between the extracellular matrix and the cytoskeleton. To gain additional insight in the molecular mechanism of neuronal degeneration in AD, here we explored the involvement of LIM kinase 1 (LIMK1), actin-depolymerizing factor (ADF), and cofilin in Abeta-induced dystrophy. ADF/cofilin are actin-binding proteins that play a central role in actin filament dynamics, and LIMK1 is the kinase that phosphorylates and thereby inhibits ADF/cofilin. Our data indicate that treatment of hippocampal neurons with fAbeta increases the level of Ser3-phosphorylated ADF/cofilin and Thr508-phosphorylated LIMK1 (P-LIMK1), accompanied by a dramatic remodeling of actin filaments, neuritic dystrophy, and neuronal cell death. A synthetic peptide, S3 peptide, which acts as a specific competitor for ADF/cofilin phosphorylation by LIMK1, inhibited fAbeta-induced ADF/cofilin phosphorylation, preventing actin filament remodeling and neuronal degeneration, indicating the involvement of LIMK1 in Abeta-induced neuronal degeneration in vitro. Immunofluorescence analysis of AD brain showed a significant increase in the number of P-LIMK1-positive neurons in areas affected with AD pathology. P-LIMK1-positive neurons also showed early signs of AD pathology, such as intracellular Abeta and pretangle phosphorylated tau. Thus, LIMK1 activation may play a key role in AD pathology.
Assuntos
Fatores de Despolimerização de Actina/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/toxicidade , Degeneração Neural/induzido quimicamente , Neurônios/efeitos dos fármacos , Fragmentos de Peptídeos/toxicidade , Proteínas Quinases/metabolismo , Doença de Alzheimer/complicações , Análise de Variância , Animais , Western Blotting/métodos , Estudos de Casos e Controles , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Córtex Cerebral/citologia , Interações Medicamentosas , Embrião de Mamíferos , Inibidores Enzimáticos/farmacologia , Imunofluorescência/métodos , Hipocampo/citologia , Humanos , Quinases Lim , Degeneração Neural/metabolismo , Fosforilação/efeitos dos fármacos , Ratos , Fatores de TempoRESUMO
The neurotoxic effect following a single intraperitoneal injection of MK-801 (10 mg/kg) in adult female Wistar rats at different survival times was studied with the 1994 version of de Olmos' Amino-Cupric-Silver (A-Cu-Ag) technique for detection of neural degeneration. In addition to the well documented somatodendritic degeneration observable in cortical olfactory structures, dentate gyrus, retrosplenial and sensory cortices, we detected this type of neuronal degeneration also in the main olfactory bulb, motor and anterior cingulate cortices, thalamus and cerebellum. Terminal degeneration, not reported by previous authors, was detected in cortical olfactory structures, hippocampal formation, sensory, infralimbic, prelimbic, agranular insular, ectorhinal, perirhinal and lateral orbital cortices. These results demonstrate that the A-Cu-Ag procedure is more efficient than other silver methods for detecting the degeneration induced by MK-801. In fact, the use of the A-Cu-Ag method has made it possible to infer the connectional relations between the damaged cell bodies and corresponding terminal degeneration. Our results also indicate that the A-Cu-Ag technique may be a suitable method for the staining of neurons undergoing apoptotic-like degeneration. The probable degenerative mechanism of MK-801 in the main olfactory system is discussed.
Assuntos
Encefalopatias/induzido quimicamente , Encéfalo/patologia , Maleato de Dizocilpina/toxicidade , Antagonistas de Aminoácidos Excitatórios/toxicidade , Degeneração Neural/induzido quimicamente , Animais , Apoptose , Encéfalo/efeitos dos fármacos , Encefalopatias/patologia , Cobre , Feminino , Ratos , Ratos Wistar , Prata , Coloração e Rotulagem/métodos , Fatores de TempoRESUMO
The strain and sex of a species under investigation may influence the animal's physiological response to a variety of stimuli. Strain and sex differences are important considerations when evaluating animal models. In the rodent MK-801 model of schizophrenia, degenerative changes occur widely in the main olfactory system and in a number of cortical brain regions. In the present report, we compare the effects of MK-801 neurotoxicity in two strains of female rats and also two lines within each strain. The magnitude and regional extent of the neurodegeneration detected with the amino-cupric-silver method varied markedly both between the Sprague-Dawley and Wistar rat strains and also between two lines derived from each strain. For example, terminal degeneration occurred in layer VI of somatosensory cortex and the central extended amygdala in Sprague-Dawley but not Wistar rats. Moreover, MK-801 treatment led to somatodendritic degeneration in the dentate gyrus of the dorsal hippocampus and basolateral amygdala in Wistar rats from Charles River Laboratories but not those from Ferreyra Institute. There are thus both strain and intrastrain differences in the magnitude of the neurodegenerative response to MK-801 treatment. The differing neurotoxicity of MK-801 between rat strains and between lines within a strain may reflect genetic variation and/or differences in hepatic biotransformation and thus the bioavailability of the drug between strains and lines within a strain.
Assuntos
Encefalopatias/genética , Maleato de Dizocilpina/toxicidade , Antagonistas de Aminoácidos Excitatórios/toxicidade , Predisposição Genética para Doença , Degeneração Neural/genética , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Encefalopatias/induzido quimicamente , Encefalopatias/patologia , Cobre , Modelos Animais de Doenças , Maleato de Dizocilpina/administração & dosagem , Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Feminino , Degeneração Neural/induzido quimicamente , Degeneração Neural/patologia , Ratos , Ratos Sprague-Dawley/genética , Ratos Wistar/genética , Prata , Especificidade da Espécie , Coloração e Rotulagem/métodosRESUMO
We evaluated serotonergic hindbrain groups of cells for their involvement in the generation and inhibition of sodium appetite. For that purpose, we analyzed the number of Fos-immunoreactive (Fos-ir) cells and double-labeled Fos-serotonin (5-HT)-ir neurons within different nuclei of the hindbrain raphe system and the area postrema (AP). Sodium depletion and sodium appetite were induced by peritoneal dialysis. Twenty-four hours after peritoneal dialysis, a 2% NaCl solution intake test was given to peritoneal dialyzed animals [PD-with access (PD-A) group] and to control dialyzed animals [CD-with access (CD-A) group]. Two additional groups of animals received either peritoneal dialysis or control dialysis but were not given access to the 2% NaCl [CD-no access (CD-NA) group or PD-no access (PD-NA) group]. The number of Fos-ir neurons within different nuclei of the raphe system was increased in spontaneous and induced sodium ingestion of CD-A and PD-A groups compared with the CD-NA and PD-NA groups. The PD-NA group had significantly fewer double-labeled cells along the raphe system compared with the animals in near-normal sodium balance (CD-NA and CD-A) or in the process of restoring sodium balance by consuming NaCl (PD-A). The AP of the PD-A group showed a significant increase in the number of Fos-ir and Fos-5-HT-ir cells compared with the PD-NA and CD groups. Our results suggest that serotonergic pathways with cell bodies in the AP and the raphe system are involved in the control of sodium appetite.