Intrauterine hypoxia-ischemia reduces phosphoinositide hydrolysis stimulated by metabotropic glutamate receptor agonists in cultured rat cerebellar granule cells

Intrauterine hypoxia-ischemia alters nitric oxide synthase expression and activity in fetal and neonatal rat brains

The effects of intrauterine hypoxia-ischemia (HI) on nitric oxide synthase (NOS) activity and on expression of NOS isoforms were investigated in fetal and neonatal rat brains. Rat fetuses were subjected to either a 30-min intrauterine HI insult or a sham operation (SH) on gestational day 17 (G17). NOS activity in the homogenate of the rat brain was detectable on G17 and increased with age. NOS activity in the HI group was 20-30% higher than in the SH group from 6 to 48 h after the HI, but was 30% lower than in the SH group from postnatal day 8 to 14. Expression of the inducible NOS (iNOS) mRNA, as examined by RT-PCR, was increased as compared to the SH group from 6 to 24 h after the HI surgery. Expression of the constitutive neuronal NOS (nNOS) mRNA was reduced in the HI group from 24 h after the HI surgery up to postnatal day 14. Immunoblotting data have shown that alterations in NOS isoform protein expression caused by the intrauterine HI were consistent with the mRNA expression data. The overall results indicate that prenatal HI has long-lasting effects on function and expression of NOS in fetal and neonatal rat brains and that the altered NOS activity may be associated with prenatal HI-induced neurological abnormalities.

Prenatal ischemia reduces neuronal injury caused by neonatal hypoxia-ischemia in rats

To determine whether 'ischemic tolerance', first described in adult rodents, exists in fetal and neonatal rats, a comparison of brain injury was made between two groups of rat pups following neonatal hypoxia-ischemia (HI). One group of rat pups had previously been subjected to HI in utero (HI + HI); the other had been subjected to a sham operation (SH + HI). Brain infarct size and neuronal injury were measured 24 h after the neonatal HI insult. As indicated by 2,3,5-triphenyltetrazolium chloride staining and pathological examination, cerebral damage was significantly less in the HI+ HI group than in the SH + HI group. Induction of heat shock protein 70 (hsp70) was immunohistochemically detectable in both groups 24 h after the neonatal HI, and was proportional to the extent of tissue damage. The ischemic tolerance phenomenon observed in immature rats does not appear to be a result of induction of hsp70.