Heterogeneity of local cerebral blood flow-PaCO2 sensitivity in neonatal dogs.

Local cerebral blood flow (1-CBF) sensitivity to changes in arterial carbon dioxide tension (PaCO2) was measured in nitrous oxide-anesthetized newborn puppies using a quantitative autoradiographic technique and [14C]antipyrine as a tracer. 1-CBF was determined in four experimental groups at PaCO2 levels of 22, 34, 48, and 65 Torr, respectively. All seven brain areas studied demonstrated 1-CBF sensitivity to altered PaCO2. There were no significant differences (P greater than 0.05) in three subcortical white matter regions (frontal, parietal, occipital) in either 1-CBF or 1-CBF-CO2 sensitivity. With the exception of the thalamus, a reciprocal relationship existed between changes in local cerebral vascular resistance and blood flow. In the thalamus, 1-CBF increased at a greater rate than the 1-CVR reduction. The results show that CBF is heterogeneous in different brain areas of the neonatal dog at normocapnia and that differences in 1-CBF-CO2 sensitivity exist.