In Vivo Real-Time Study of Drug Effects on Carotid Blood Flow in the Ovine Fetus

The ability of an organism to maintain a constant blood flow to the brain in response to sudden surges in systemic blood pressure (BP) is known as cerebral autoregulation (CAR), which occurs in the carotid artery. In contrast to full-term neonates, preterm neonates are unable to reduce the cerebral blood flow (CBF) in response to increased systemic BP. In preterm neonates, this exposes the fragile cerebral vessels to high perfusion pressures, leading to their rupture and brain damage. Ex vivo studies using wire myography have demonstrated that carotid arteries from near-term fetuses constrict in response to the activation of adrenergic alpha1 receptors. This response is blunted in the preterm fetus. Thus, to examine the role of alpha1-AR in vivo, presented here is an innovative approach to determine the effects of drugs on a carotid arterial segment in vivo in an ovine fetus during the developmental progression of gestation. The presented data demonstrate the simultaneous measurement of fetal blood flow and blood pressure. The perivascular delivery system can be used to conduct a long-term study over several days. Additional applications for this method could include viral delivery systems to alter the expression of genes in a segment of the carotid artery. These methods could be applied to other blood vessels in the growing organism in utero as well as in adult organisms.