Effect of sympathetic stimulation on permeability of the blood-brain barrier to albumin during acute hypertension in cats.

Abstract

Most studies of effects of neural stimuli on the cerebral circulation have focused on changes in cerebral blood flow (CBF). Effects of sympathetic nerves on permeability of the blood-brain barrier (BBB) to albumin were examined by a quantitative method, and changes in blood flow were related to changes in permeability of the BBB. Permeability of the BBB was evaluated by measuring the accumulation of 131I-labeled serum albumin (RISA) in brain. RISA was injected i.v. and the ratio of brain RISA to blood RISA was used as an index of permeability of the BBB. In normotensive cats, the BBB index in the cerebrum was 0.12 .+-. 0.04% (mean .+-. SE). During acute hypertension produced by i.v. norepinephrine, the BBB index in the cerebrum increased to 0.91 .+-. 0.20% (P < 0.05). Sympathetic stimulation during hypertension attenuated the increase in BBB index: the BBB index was 0.38 .+-. 0.10% and 1.01 .+-. 0.26% on the stimulated and unstimulated sides of the cerebrum, respectively (P < 0.05). CBF increased more than 3-fold during severe hypertension; sympathetic stimulation attenuated the increase in flow. Increases in flow, disruption of the BBB and responses to sympathetic stimulation were largest in cortical grey matter. Disruption of the BBB during hypertension was minimal in subcortical grey and white matter and sympathetic stimulation had no detectable effect in these areas. Acute hypertension increases the permeability of the BBB to albumin and sympathetic stimulation reduces disruption of the barrier. The regions of the brain most susceptible to disruption of the BBB were most responsive to the protective effect of sympathetic stimulation.