RESUMO
BACKGROUND: In addition to the hippocampus, the dorsolateral caudate nucleus (CN) and the pars reticularis of the substantia nigra (SNr) are among the most vulnerable brain areas to ischemia. A possible association of the neuronal injury in these two subcortical nuclei has been proposed, the primary damage affecting the CN GABAergic neurons innervating the SNr, and secondarily the SNr neurons as a result of an imbalance of GABAergic and glutamatergic input to the SNr. Progesterone (P(4)) exerts a GABAergic action on the central nervous system (CNS) and is known to protect neurons in the cat hippocampus from the damaging effect of acute global cerebral ischemia (AGCI). The effects of AGCI on the neuronal populations of the CN and SNr, in addition to the possible neuroprotective effects of P(4), were assessed in cats in the present study. METHODS: Ovariectomized adult cats were treated subcutaneously (s.c.) with either P(4) (10 mg/kg/day) or corn oil during the 7 days before and 7 days after being subjected to a period of AGCI by 15 min of cardiorespiratory arrest followed by 4 min of reanimation. After 14 days of survival, animals were sacrificed and their brains perfused in situ with phosphate-buffered 10% formaldehyde for histologic examination. RESULTS: ACGI resulted in an intense glial reaction in the CN and a significant loss (43%) of medium-sized neurons of the CN, but no difference was found in the densities of SNr neurons between controls and ischemic oil- and P(4)-treated cats. Progesterone treatment completely prevented CN neuronal loss. CONCLUSIONS: The overall results point to the higher vulnerability of CN neurons to ischemia as compared to neurons in the SNr and show the protective effects of P(4) upon CN neuronal damage after ischemia.
Assuntos
Isquemia Encefálica/patologia , Núcleo Caudado/patologia , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Progesterona/farmacologia , Substância Negra/patologia , Animais , Isquemia Encefálica/fisiopatologia , Gatos , Núcleo Caudado/efeitos dos fármacos , Feminino , Parada Cardíaca , Neurônios/metabolismo , Fármacos Neuroprotetores/administração & dosagem , Ovariectomia , Progesterona/administração & dosagem , Distribuição Aleatória , Substância Negra/efeitos dos fármacosRESUMO
Background. Barbiturates, benzodiazepines, and synthetic steroids having anesthetic properties, by enchacing the inhibitory GABAergic neurotransmission to the neruronal circuits of cerebral structures vulnerable to ischemia, reduce the damage induced by this condition. Some endogenous steroids resulting from progesterone (P4) biotransformation in the brain exert GABAaergic effects, thus inhibiting neuronal excitability. Hence, P4 administration both before and after an experimentally induced ischemic episode may prevent or decrease the ischemic cerebral damage. Methods. Ovariectomized adult cats were treated sc with either P4 (10 mg/kg/day) or corn oil during 7 days before and 7 days after being subjected to a period of acute global cerebral ischemia by 15 min of cardiorespiratory arrest followed by 4 min of reanimation. After 14 days of survival, animals were sacrificed and the brains perfused in situ and formalin-fixed for histological examination. Results. Acute global cerebral ischemia resulted in a severe loss of neurons (54-85 percent), mainly in CA1 and CA2 subfields of oil-treated cats. Progesterone significantly reduced the neuronal loss in those areas (21-49 percent). Conclusions. Overall results suggest that progesterone exerts protective effects against the neuronal cerebral damage induced by acute global cerebral ischemia
Assuntos
Animais , Feminino , Gatos , Hipocampo/irrigação sanguínea , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Ataque Isquêmico Transitório/patologia , Ataque Isquêmico Transitório/prevenção & controle , Fármacos Neuroprotetores/uso terapêutico , Progesterona/uso terapêuticoRESUMO
Electroencephalographic and clinical signs of epileptoid activity have been associated with the administration offentanyl during surgery in patients. These phenomena have been in turn related to changes in metabolic rate, oxygen consumption, and blood flow in specific brain structures both in humans and experimental animals. However, direct evidence showing changes in neuronal firing in specific brain regions during fentanyl-induced epileptoid activity has not been reported. Eight adult male cats with chronically implanted bipolar electrodes in the mesencephalic reticular formation, hippocampus, amygdala, and parieto-occipital cortex were included in the study. Different treatments i.e., vehicle-fentanyl or diazepam-fentanyl, were administered to the experimental animals at 7-day intervals under neuromuscular blockade and assisted ventilation. Electroencephalographic (EEG) seizures, grouped and isolated spikes, and significant increases of multineuronal activity (MUA) were elicited by fentanyl, 50 µg/kg iv, in these brain structures. Both EEG and MUA changes reached their maximal values within 6 min of fentanyl administration, and then diminished as time elapsed. Diazepam, 100, 200, or 400 µg/kg, but not 50 µg/kg iv, significantly reduced or prevented the fentanyl-induced epileptoid EEG activity and MUA increases. The present results show that both entanyl- induced epileptoid EEGactivity as wel as the concomitant increase in MUA of brain subcortical structures are part of the same epileptogenic phenomenon, mainly generated at limbic structures. In addition, the effects of fiazepamagainst both epileptoid EEG activity and increase of MUA of brain subcortical structures support the use of benzodiazepine as premedicants for fentanyl anesthesia in order to prevent or to reduce epileptoid phenomena that can results from opioid administration during the anesthetic procedures
Assuntos
Gatos , Animais , Masculino , Gatos/fisiologia , Cérebro/ultraestrutura , Diazepam/farmacocinética , Eletroencefalografia/métodos , Epilepsia/induzido quimicamente , Fentanila , Mesencéfalo/fisiologia , Sistema Límbico/fisiologiaRESUMO
Se estudiaron los efectos de la administración de la mezcla de alfaxalona-acetato de alfadolona (27.07 uM/Kg-7.68 uM/Kg) sobre el daño neurológico consecutivo a la isquemia cerebral global aguda provocada por paro cardiorespiratorio (CRA) de 8 min de duración en gatos
Assuntos
Animais , Isquemia Encefálica , Sistema Nervoso Central/efeitos dos fármacos , Córtex Cerebral , Eletroencefalografia , Parada Cardíaca , Formação ReticularRESUMO
La correlación entre el tiempo de paro cardiorrespiratorio (10 min.) inducido experimentalmente en gatos con las modificaciones concomitantes de pH (0.16 unidades/min), déficit de exceso de base (0.97 mEp/L/min) y otros componentes sanguíneos, así como el análisis de regresión de los valores del déficit del exceso de base durante el paro cardiorrespiratorio permitieron calcular la dosis de bicarbonato de sodio adecuada para la corrección inmediata de la acidosis metabólica durante los procedimientos de reanimación correspondientes tras cinco minutos de paro cardiorrespiratorio en gatos, aunque también provocó hipopotasemia y hiperosmolaridad. En condiciones similares, la dosis de bicarbonato de sodio calculada sin tomar en cuenta la relación entre tiempo de paro cardiorrespiratorio y déficit de exceso de base fue insuficiente para normalizar el pH. Los resultados indican la importancia de dichos factores y la posibilidad de predeterminar la dosis adecuada de bicarbonato de sodio para el tratamiento del paro cardiorrespiratorio
Assuntos
Gatos , Animais , Acidose/sangue , Bicarbonatos/uso terapêutico , Parada Cardíaca Induzida , Acidose/tratamento farmacológicoRESUMO
La ingestión y la succión de leche indujeron sincronización del EEG (6-10 cps, 150-180 v) en el área parietooccipital y el hipocampo coincidente con inhibición de la actividad multiunitaria (MUA) de la formación reticular mesencefálica, el hipocampo dorsal y los núcleos hipotalámicos ventromedial y paraventricular. las proporciones de sincronización EEG variaron en diferentes animales (20 gatas lactantes) de 2 por ciento a 60 por ciento del tiempo total de succión, o de 3 por ciento a 77 por ciento del tiempo total de ingestión de leche. La presencia y la magnitud de la sincronización EEG durante la succión no tienen relación con el rendimiento lácteo, pero parecen estar relacionadas con el estado de ánimo de las gatas, espontáneo o inducido por fármacos. Los cambios del EEG y la MUA provocados por la succión son idénticos a las manifestaciones electrográficas de la "conducta de relajación" de los gatos durante ingestión de leche, acicalamiento, estimulación perineal o acariciamiento; de este modo, puede concluirse que son parte de la reacción integral de las gatas lactantes ante los estímulos de la succión, los cuales producen "conducta de relajación""
Assuntos
Gatos , Animais , Eletroencefalografia , Leite/fisiologia , Relaxamento , Comportamento de SucçãoRESUMO
Se investigaron los efectos de diferentes dosis de diacepam (0.1,0.3,1.0,3.0 mg/kg IM) o metocarbamol (30,100,300 mg/kg IM) en diez gatos que mostraban comportamiento aprensivo y escasas proporciones de sincronización del EEG parietal y parietooccipital durante la ingestión de leche, un signo electrografico confiable de la "conducta de relajación" en el gato. Las proporciones de sincronización del EEG parietal y parietooccipital aumentaron significativamente luego de la administración de estos fármacos; al parecer este efecto del diacepam se relaciona principalmente con los efectos del fármaco sobre la conducta que también suprimió el comportamiento aprensivo. El efecto del metocarbamol, aumentó de la sincronización del EEG durante la ingestión de leche, podría ser causado principalmente por cambios del estado de ánimo resultantes de la relajación muscular. Estos hallazgos deben considerarse para el análisis de los mecanismos nerviosos que relacionan el estado de ánimo, el tono muscular y los signos electrográficos de la "conducta de relajación