[Comparative analysis of cerebral blood flow autoregulation in pregnant and nonpregnant rats]

It is known, that disturbances in functioning of cerebral blood flow autoregulation during pregnancy may cause severe neurological complications in case of hypertensive episodes. The aim of this study was comparison of autoregulatory responses of cerebral blood flow in pregnant and nonpregnant rats and analysis of their possible mechanisms. Experiments were carried out on two groups of nonpregnant white rats, and two groups of late-pregnant. All test on autoregulation of cerebral blood flow were provided in conditions of acute experiment under chloral hydrate anesthesia. Gradual changes in systemic arterial pressure were caused by occlusion of abdominal aorta by means of catheter with inflatable tip. The local cerebral blood flow was registered using Hydrogen Clearance technique. Before beginning of autoregulatory tests two groups of animals were treated with nitric oxide synthase inhibitor L-NAME. It was established that in late-pregnancy the cerebral blood flow autoregulatory curve in comparison with nonpregnant animals is shifted to the low levels of systemic arterial pressure. Inhibition of nitric oxide synthase by L-NAME caused the shift of autoregulatory curve to the high levels of systemic arterial pressure in both nonpregnant and pregnant animals. Besides, the differences in autoregulatory responses between nonpregnant and pregnant animals taking place in untreated by L-NAME groups were completely eliminated. These finding allow concluding that in late-pregnancy the shift of cerebral blood flow autoregulatory curve to low levels of systemic arterial pressure is caused by increased production of nitric oxide.