Perinatal hypoxia ischemia (HI) is a frequent cause of neonatal brain injury. This study aimed at describing molecular changes during the first 48 h after exposure of the neonatal rat brain to HI. Twelve-day-old rats were subjected to unilateral carotid artery occlusion and 90 min of 8% O 2 , leading to neuronal damage in the ipsilateral hemisphere only. Phosphorylated-Akt levels were decreased from 0.5 to 6 h post-HI, whereas the level of phosphorylated extracellular signal-related kinases (ERK)1/2 increased during this time frame. Hypoxia-inducible factor (HIF)-1␣ protein increased with a peak at 3 h after HI. mRNA expression for IL-␤ and tumor necrosis factor-␣ and -␤ started to increase at 6 h with a peak at 24 h post-HI. Expression of heat shock protein 70 was increased from 12 h after HI onwards in the ipsilateral hemisphere only. Surprisingly, HI changed the expression of cytokines, HIF1-␣ ,and P-Akt to the same extent in both the ipsi-as well as the contralateral hemisphere, although neuronal damage was unilateral. Exposure of animals to hypoxia without carotid artery occlusion induced similar changes in cytokines, HIF-1␣, and P-Akt. We conclude that during HI, hypoxia is sufficient to regulate multiple molecular mediators that may contribute, but are not sufficient, to induce long-term neuronal damage. A commonly used neonatal rat model to investigate hypoxic-ischemic brain damage is the Vannucci-Rice model. This model implicates unilateral common carotid artery ligation followed by inhalation of 8% O 2 for 1-2 h. This procedure leads to cerebral damage restricted to the hemisphere ipsilateral to the occluded artery (4).Early after induction of cerebral damage, death, and survival, kinase signalling pathways are known to be activated, including the phosphatidyl-inositol 3 kinase/Akt (PI3-K/Akt) and the ERK1/2 pathways. The phosphorylated forms of these kinases have been shown to be up-regulated after HI in vivo as well as in vitro and are thought to be involved in neuronal cell apoptosis (5-7). Activation of the PI3-K/Akt and the ERK1/2 signaling routes enhance translation of the transcription factor HIF-1␣ (8 -10). In addition, reduced cellular oxygen levels increase the stability of HIF-1␣ protein. More than 40 genes containing the promoter sequence for HIF-1␣ have been identified. Most of these genes play a key role in neuroprotective processes such as angiogenesis/vascular remodeling, erythropoiesis, glucose transport, glycolysis, iron transport, and cell proliferation/neuronal survival (11). Increased HIF-1␣ levels therefore regulate adaptation of the cell to a hypoxic environment (12). Another factor induced after HI that has been implicated in both cellular protection and damage, is HSP70. HSP70 is a chaperone molecule, which is induced in cells after stress such as heat, stretch, or hypoxia (13,14). Intracellular HSP70 is thought to protect cells by binding to denatured proteins, thereby preventing further denaturation or degradation of the proteins. In addition, there is evidence that...

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In this study, we tested the hypothesis that combined inhibition of nNOS and iNOS will reduce neuronal damage and the inflammatory response induced by perinatal hypoxia-ischaemia (HI). In 12-day-old rats, HI was induced by right carotid artery occlusion followed by 90 min of 8% O₂. Immediately upon reoxygenation, the rats were treated with NOS inhibitors (n = 24) or placebo (n = 24). Neuropathology was scored at 6 weeks after HI on a 4-point scale (n = 12 per group). The expression of heat shock protein 70 (HSP70) and mRNA expression for cytokines were measured 12 h after HI (n = 12 per group). Histopathological analysis showed that the ipsilateral hemisphere in the NOS inhibition group was less damaged than in the placebo group (p < 0.05). HI induced a significant increase in HSP70 levels (p < 0.05) in the ipsilateral hemispheres, which tended to be lower in the NOS inhibition group (p = 0.07). HI induced an increase in mRNA expression for IL-1β, TNF-α and TNF-β, but there was no difference between the ipsi- and contralateral hemispheres. Combined inhibition of nNOS and iNOS did not induce any change in cytokine expression. We conclude that the long-term neuroprotective effects of combined nNOS and iNOS inhibition were not achieved by an altered cytokine response.