ABSTRACT
Objective:To investigate the blocking effect of non-competitive N-methyl-D-aspartic acid(NMDA) receptor antagonist Memantine on glutamate abnormal signal transmission in immature white matter induced by ischemia in vitro and in vivo. Methods:The oligodendrocyte (OL) precursor oxygen glucose deprivation (OGD) cell models of 2-day-old newborn rats were prepared and divided into the normal control group, the OGD group and the Memantine group.The extracellular glutamate level of the OL precursor was measured by high performance liquid chromatography, while the concentration of intracellular calcium and the apoptosis rate of OL precursor were detected by flow cytometry.The animal models of ischemic periventricular leukomalacia (PVL) were established and divided into the sham group, the PVL group and the Memantine group.The pathological evaluation of white matter was performed under light microscope.The positive OL expression rate of myelin basic protein(MBP) was detected by immunohistoche-mistry.The myelination of white matter was evaluated under electron microscope.Results:Compared with the normal control group in vitro, the OGD group had a higher extracellular glutamate level of the OL precursor [(24.60±2.42) μmol/L vs.(9.49±1.08) μmol/L, t=9.28, P<0.01], a higher intracellular calcium concentration [(32.9±6.9)% vs.(6.9±3.5)%, t=4.41, P<0.01], a higher apoptosis rate of the OL precursor [(24.77±2.05)% vs.(6.65±1.39)%, t=15.01, P<0.01]. After treatment with Memantine, the extracellular glutamate level [(14.70±1.70) μmol/L, t=5.68, P<0.01], the intracellular calcium concentration [(23.1±2.0)%, t=6.13, P<0.01], and the apoptosis rate of the OL precursor [(11.80±2.06)%, t=5.18, P<0.01] decreased significantly.Compared with the sham group in vivo, the white matter of the PVL group showed mild or severe pathological changes, and the PVL group had a lower MBP-positive OL expression rate in the white matter [(5.94±1.37)% vs.(15.40±3.22)%, t=4.63, P<0.01]less myelin sheaths (4.00±1.00 vs.14.67±2.70, t=6.11, P<0.01) and thinner myelin sheaths [(33.83±3.21) nm vs.(79.67±6.45) nm , t=10.43, P<0.01]. After the treatment with Memantine, the number of myelin sheaths (10.30±1.50, t=6.01, P<0.01), the thickness of myelin sheaths [(57.21±4.05) nm, t=7.47, P<0.01], and the pathological changes in the white matter of newborn rats ( Z=88.479, P<0.01) all improved markedly, and the MBP positive OL expression rate in the cerebral white matter [(11.02±1.35)%, t=4.40, P<0.05] also increased significantly. Conclusions:Ischemia-induced abnormal signal transmission of glutamate in immature white matter is the important pathway leading to ischemic PVL.Memantine can effectively block the abnormal signal transmission and thus may probably provide a new approach for the effective prevention and treatment of PVL in premature infants.