Age-related ischemia in the brain following bilateral carotid artery occlusion--collateral blood flow and brain metabolism.

Cerebral blood flow (CBF) and cerebellar blood flow (CeBF) were measured and correlated with brain lactate, pyruvate and adenosine triphosphate concentrations from groups representing 3-week old suckling (n = 10), 18-22-week old adult (n = 9) and 70-week old aged (n = 7) Sprague-Dawley rats before and during bilateral carotid occlusion (BCO). The steal ratio, calculated as the ratio of %control CBF to %control CeBF, was 1.02 +/- 0.06 (mean +/- SEM) at 60 minutes of BCO in adult rats that exhibited normal levels of brain metabolites. By contrast, the ratios significantly decreased to 0.74 +/- 0.06 in suckling rats and 0.69 +/- 0.06 in aged rats with simultaneous increases by 2.4 to 2.9-fold of tissue lactate. Pyruvate and lactate/pyruvate ratio also increased by 1.4 to 1.8 times control in both suckling and aged rats. We conclude that there is age-related steal phenomenon occurring with blood flow during BCO. Ischemic derangement of the brain metabolism is in part related to poor blood supply from the posterior circulation in suckling and aged rats.