INTRAUTERINE HYPOXIA-ISCHEMIA INCREASES N-METHYL-D-ASPARTATE-INDUCED CGMP FORMATION AND GLUTAMATE ACCUMULATION IN CULTURED RAT CEREBELLAR GRANULE CELLS

Effects of intrauterine hypoxia-ischemia (HI) on brain functional deve lopment in the term rat were examined in cerebellar granule cell cultu res obtained from an in utero HI model. On gestation d 17, HI conditio ns were achieved by complete clamping of the uterine vasculature for d esignated durations followed by removal of the clamps to permit reperf usion. Sham operation (surgery without vasculature clamping) was perfo rmed as the control. After surgery, the uterine horns were returned to dam's abdomen to let the pups deliver naturally. Severe HI insult fro m the surgical manipulation was evident in that the lactate levels of fetal brain increased, and fetal blood pH decreased with the duration of vasculature clamping up to 1 h. The experimental KI insult up to 1 h did not affect fetal survival rate, but retarded growth of fetuses o r newborns was observed in the 1 h HI group. N-Methyl-D-aspartate (NMD A)- and kainate (KA)-stimulated cGMP formation and glutamate accumulat ion were measured in cerebellar granule cell cultures from 8-d-old pup s suffering from various durations of antenatal HI insult. NMDA (100 m u M)-induced elevation of cGMP was further augmented by a 10-35-min HI insult as compared with the control cells (62.4-78.2 versus 49 pmol/m g protein). In the presence of L-N-G-monomethyl-arginine (L-NMMA, 150 mu M), a nitric oxide synthase inhibitor, NMDA-induced cGMP formation was blocked, and the blockade of cGMP formation by L-NMMA (10 mu M) co uld be reversed by simultaneous application of 1 mM arginine in both c ontrol and HI cells. Antenatal HI insult (20-35 min) also augmented NM DA-, but not KA-, stimulated accumulation of extracellular glutamate. The hypersensitive response in NMDA-induced glutamate accumulation cou ld be suppressed by 150 mu M L-NMMA. The overall results suggest that antenatal HI occurring in the last half of gestation may result chroni cally in adverse effects on NMDA receptor-mediated neurotransmission a nd that nitric oxide is possibly involved in these effects.