Hypoxic fetal programming of the sympathetic nervous system

Abstract

The link between intra uterine growth restriction (IUGR) and increased risk of adult cardiovascular disease in the offspring is well established. Chronic hypoxia in utero (CHU) is a well established cause of IUGR, and using in vitro methods, has been shown to cause endothelial dysfunction and sympathetic hyperinnervation in the offspring. Our aim is to assess the impact of CHU upon sympathetic nerve activity. We have made direct recordings of MSNA from arteries supplying the Spinotrapezius muscle under Alfaxan anaesthesia in Normal (N, n=7) and CHU rats (n=6), discriminating single unit activity from multiunit recordings. Arterial blood pressure, measured from the femoral artery, was similar in N and CHU rats (N:123±3, CHU: 119±5, mmHg). All single units (N=17, CHU=26) had cardiac and respiratory rhythmicity. Mean firing rates were similar (N: 0.48±0.09, CHU: 0.52±0.1, Hz). Further analysis showed that high frequency doublets and triplets of activity (>20hz) were more common in CHU. This may suggest increased release of Neuropeptide Y from sympathetic varicosities, and hence, impact upon cardiovascular health. Recordings during baro- and chemoreceptor stimulation are under analysis.