Maternal hypertension during pregnancy modifies the response of the immature brain to hypoxia-ischemia: Sequential MRI and behavioral investigations

Hypoxic-ischemic (HI) brain injury occurring during the perinatal period is still a major cause of mortality and morbidity. We assessed the impact of maternal hypertension, the most common medical disorder of pregnancy, on the anatomical and functional consequences of HI insult in the immature brain. Rat pups from spontaneously hypertensive (SHR) and normotensive (Wistar Kyoto - WKY) dams were subjected to HI brain damage at postnatal day 7 (P7). Brain lesion and functional deficits were analyzed from 10 min to 35 days after HI, using magnetic resonance imaging (MRI), sensorimotor and cognitive tests. MRI data revealed that SHR pups displayed less brain damage than WKY, attested by an initial smaller lesion followed by a reduced tissue loss at chronic stage (57.1±21.6 and 31.1±27% ipsilateral hemisphere atrophy in WKY and SHR, respectively). Behavioral analyses showed less HI-induced behavioral deficits in motor coordination (rotarod test) and spatial learning (Morris watermaze test) in pups from hypertensive dams compared to those from normotensive ones. The data suggest that maternal hypertension causes prenatal stress that may render the immature brain more resistant to subsequent hypoxia-ischemia, related to a preconditioning phenomenon. (authors)