The intracarotid 133xenon injection method for measurement of cerebral blood flow (CBF) in rats: evaluation of the effect of bolus volume.

It is assumed that the cerebral microcirculation is not perturbed by the intraarterial injection used in determination of cerebral blood flow (CBF) with the intraarterial 133Xenon technique (and in various assessments of blood brain barrier (BBB) permeability). The application of these techniques to the rat, where the injectate is large compared to normal blood flow, places this problem is focus and it has been claimed that since large intracarotid injections increased cerebral venous outflow, the CBF must also increase. We investigated this problem in the rat by means of the intraarterial 133Xenon injection technique, using a saline bolus injected in less than 1 sec and found that CBF was unaltered at bolus volumes between 10 and 100 microliters. Furthermore, injection of 100-200 microliters saline during washout detection did not change the slope of the semilogarithmic wash-put curves. It is concluded that in spite of large intracarotid injections the CBF remained constant and that the hemodilution produced by the saline bolus is not sufficient to influence CBF. Consequently, estimations of CBF yield valid results in the present rat preparation.