Abstract
The blood-brain barrier (B-BB) in 3-month-old rats was opened unilaterally by infusing 1.8 m l(+)arabinose in water into the internal carotid artery through a catheter in the external carotid. Two poorly penetrating uncharged test radiotracers of differing molecular weight and size, [ 14C]sucrose (340 daltons, radius 5 Å) and [ 3H]inulin (5500 daltons, radius 15 Å), were simultaneously injected i.v. in untreated rats, or in rats at 1, 30, or 50 min after infusion of hypertonic arabinose solution. Evans-blue solution was injected 5 min prior to osmotic treatment as a visual indicator of barrier integrity. In regions of uninfused control brains, the [ 14C]sucrose permeability-surface area ( PA) product approximated 10 −5 s −1, whereas PA was not measurable for [ 3H]inulin. In arabinose-infused animals, PA products on the ipsilateral hemisphere for both [ 14C]sucrose and [ 3H]inulin were markedly elevated 6 min after infusion, but decreased by 35 and 55 min. In nearly all regions, statistically significant differences were not found between 6-min [ 14C]sucrose- and [ 3H]inulin-PA values ( P > 0.05). However, at 35 and 55 min in most regions, the PA for [ 3H]inulin was significantly lower ( P < 0.05) than PA for [ 14C]sucrose. The results indicated that the B-BB closed more rapidly to larger than to smaller molecules after osmotic treatment and were consistent with a pore model for osmotic B-BB opening.
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