Preventive effects of exogenous phospholipases on inhibition by ferrous ions of [3H]MK-801 binding in rat brain synaptic membranes

Protective role of pentobarbital pretreatment for NMDA-R activated lipid peroxidation is derived from the synergistic effect on endogenous anti-oxidant in the hippocampus of rats

We have attempted to explore the neuroprotective effectiveness of PBT by measuring anti-oxidant ability in the hippocampus of rats in a freely moving state. Anti-oxidant ability was examined utilizing the principle that blood-brain barrier-permeable nitroxide radicals (PCAM) injected i.p. lose their paramagnetism in an exponential decay correlated with anti-oxidant ability in the brain. The half-life of PCAM was used as the indicator of the hippocampal anti-oxidant ability. While the half-life was statistically prolonged when infused with 0.1mM NMDA without PBT, the half-life was almost the same as in the control when infused with NMDA under anesthesia with PBT. In addition, the half-life under only PBT anesthesia was the shortest of all the groups. Our findings, therefore, suggested that PBT anesthesia not only suppresses NMDA-R activated free radical generation but also synergistically enhances the increased basal endogenous anti-oxidant ability in the hippocampus.

Possible correlation between abilities of a variety of polyamines to increase activator protein-1 DNA binding and to inhibit [3H]spermidine transport in nuclear fractions of murine brain

The addition of a number of natural and synthetic polyamines significantly increased activator protein (AP1) DNA binding in nuclear extracts of murine whole brain, which occurred in a manner positively correlated with their potencies to inhibit temperature-dependent transport of [3H]spermidine in brain nuclear fractions. These results suggest that polyamines may affect gene transcription by AP1 complex after incorporation into the nucleus in rodent brain.

Blockade by ferrous iron of Ca2+ influx through N-methyl-D-aspartate receptor channels in immature cultured rat cortical neurons

Rat cortical neurons cultured for 3 days in vitro were loaded with the fluorescent indicator fluo-3 for assessment of intracellular free calcium ion (Ca2+) concentrations with the aid of a confocal laser-scanning microscope. In the absence of added MgCl2, the addition of NMDA induced a rapid but sustained increase in the number of fluorescent neurons in a concentration-dependent manner at a concentration range of 1-100 micro m with the increase by KCl being transient. The addition of FeCl2, but not FeCl3, markedly inhibited the increase by NMDA in a reversible manner at concentrations of 10-200 micro m, without affecting that by KCl. Extensive analyses revealed clear differentiation between inhibitions by ferrous iron and other channel blockers known to date. The inhibition by FeCl2 was completely prevented by the addition of two different iron chelators. Exposure to NMDA alone did not lead to cell death in immature cultured neurons, however, while further addition of FeCl2 invariably induced neuronal cell death 24 h after exposure. These results give support to our previous proposal that NMDA receptor complex may contain a novel site sensitive to blockade by ferrous iron in rat brain.

Nitric oxide and hydroxyl radicals initiate lipid peroxidation by NMDA receptor activation

In this experiment, we used direct electron paramagnetic resonance (EPR) spectra to measure lipid peroxidation by hydroxyl radical (.OH), nitric oxide (.NO) and lipid radical (.L). NMDA-receptor associated lipid peroxidation is thought to act through .OH in induction of neurotoxicity. The origin of .OH generation was found to arise mainly from peroxynitrite anion produced from O(2)(-) and .NO rather than from Fenton's reaction. This study verified that .OH generation from interactive reactions between .NO and O(2)(-) initiates NMDA-induced lipid peroxidation of PC12 cells.