Inibição do receptor de glutamato do tipo NMDA em um modelo de hipóxia-isquemia prenatal: avaliação morfofuncional do cerebelo / Inhibition of glutamate NMDA receptor in a prenatal hipoxia-ischemia model: morphofunctional analises of cerebellum

Lesões sistêmicas peri e pré-natais alteram o desenvolvimento do SNC, levando a problemas cognitivos e motores em crianças que podem perdurar por toda a vida. Um tipo particular de lesão é a hipóxia-isquemia (HI), caracterizada pela interrupção momentânea ou permanente do fluxo sanguíneo. Um dos mecanismos propostos para as lesões decorrentes da HI é a excitotoxicidade glutamatérgica. O uso de inibidores da neurotransmissão glutamatérgica tem sido estudados em diversos modelos de HI. Neste trabalho, avaliamos os efeitos morfofuncionais da administração de um antagonista não-competitivo do receptor de glutamato NMDA sobre o desenvolvimento do cerebelo. Ratas no 18º dia de gestação foram anestesiadas, os cornos uterinos expostos e as 4 artérias uterinas obstruídas por 45 minutos (Grupo H). Animais controle tiveram os úteros expostos, sem a obstrução (Grupo S). Após a cirurgia a gestação prosseguiu. Somente animais nascidos a termo foram utilizados. Um dia após o nascimento, metade de cada ninhada foi designada para receber MK801, 0,3mg/kg/dia, (grupos SM e HM) e a outra metade recebeu solução salina (grupos SS e HS), por 5 dias. Após anestesia e perfusão-fixação com paraformaldeído 4% aos 9, 23, 30 e 60 dias pós-natais, cortes parassagitais do cerebelo foram obtidos em criótomo e submetidos à imunohistoquímica para calbindina, GFAP, GLAST, PDGFRα e MBP. A partir de 45 dias de vida, os animais foram testados em vários de testes comportamentais: labirinto em cruz elevado (LCE), campo vazado (CV), ROTAROD, teste de caminhada sobre barras (ladder test) e teste do comprimento da passada (stride length). Aos 9 dias, a espessura da árvore dendrítica era menor nos animais SM, HS/HM, demonstrando efeitos deletérios tanto do MK801 quanto da HI. Menor número de células PDGFRα+ foi observado nos animais HS/HM, sem efeitos da administração de MK801. Aos 23 dias, maior número de células PDGFRα+ foi observado nos animais HM comparado aos outros 3 grupos, indicando efeito ...

Peri and prenatal systemic lesions alter CNS development leading to motor and cognitive problems in children that might persist throughout life. A particular kind of injury, the hypoxic ischemic (HI), is characterized by a permanent or temporary blockage of blood flow. One of the proposed mechanisms downstream from a HI event is called glutamatergic excitotoxicity. The administration of glutamate inhibitors has been studied in HI models for several years. In this work, we evaluated the effects of administration of a non-competitive antagonist of glutamate receptor, NMDA, on cerebellar development and behavioral tests of HI animals. Pregnant rats in the 18th gestational day were anesthetized, the uterine horns were exposed and the four uterine arteries were clamped for 45 minutes (group H). Sham controls had the uterine horns exposed, but no arteries were clamped (group S). Gestation proceeded after surgery. Only full term animals were used. One day after birth half the animals was assigned to receive either SALINE (groups SS and HS) or MK801 (groups SM and HM). Animals were anesthetized and perfused with 4% paraformaldehyde at 9, 23, 30 and 60 days of age. Parasagittal cerebellar sections were submitted to Calbindin, GFAP, GLAST, PDGFRα and MBP immunohistochemistry. Beginning at P45 animals were subjected to a battery of behavioral tests: elevated plus maze (EPM), hole board (HB), ROTAROD, ladder test and stride length. At P9 the dendritic tree of Purkinje cells were thinner in SM, HS/HM animals, indicating that both HI and MK801 are deleterious regarding this Purkinje cell differentiation. A lower number of PDGFRα+ cells was observed in HS/HM animals, with no effects of MK801 administration. At P23 a greater number of PDGFRα+ cells was found in HM animals when compared to the other 3 groups, demonstrating a neuroprotector effect of MK801. A lower number of myelinated fibers (MBP+) was observed in HS animals at P9, and MK801 administration reverse this ...

Motor and electrographic response of refractory experimental status epilepticus in rats and effect of calcium channel blockers.

Effects of various calcium channel inhibitors have been studied in lithium-pilocarpine model of status epilepticus. Status epilepticus was induced by administration of lithium chloride (3 meq/kg) followed 21 hr later by pilocarpine (30 mg/kg). Diltiazem (5 and 10 mg/kg) was not effective in delaying onset of convulsions. Verapamil (20 mg/kg) showed protection against lithium-pilocarpine-induced convulsions. The dihydropyridine nifidepine (2.5 and 5 mg/kg) did not show any protection in this model. Amlodipine (5 and 10 mg/kg) as partially protective. Flunarizine (10 and 20 mg/kg) delayed the onset of forelimb clonus and rearing and only 60% of the rats underwent status in the 20 mg/kg group. Pre-treatment of MK-801 led to a potentiation of the antiseizure activity of calcium channel inhibitors. The percent increase in amplitude at various time points with amlodipine pretreatment was significant only at the 30th min recording, and at the rest of the time frames was practically similar as the controls. It can be concluded that the anticonvulsant action of MK-801 can be enhanced by centrally acting calcium channel inhibitors.