Evaluation of in vivo brain site perfusion with the push-pull cannula

The effect of tissue site perfusion with push-pull cannulas on the integrity of brain tissue was evaluated during in vivo studies in conscious New Zealand rabbits. The mean rate of perfusion-induced tissue disruption was 1.09 microgram tissue wet wt/min as estimated from the perfusate levels of endogenous nervous system specific proteins (S-100 and 14-3-2). The level of intravenously injected 125I-labeled bovine serum albumin recovered in perfusate samples indicated that approximately 2.0 nl serum/min penetrated the vascular barrier into the perfused tissue site. The appearance of intraventricularly injected solutes in perfusate samples was subjected to regression analysis. It was demonstrated that nonspecific variations in the appearance of one substance in the perfusate could be controlled for by a regression on the levels of another concurrently recovered inert substance. The experiments demonstrate that tissue site perfusion can provide useful access to brain extracellular fluid when suitable controls are incorporated for recovery variation and blood-brain barrier seepage.