POTENTIAL MECHANISMS OF THE AGE-RELATED-CHANGES IN THE BLOOD-BRAIN-BARRIER

A variety of age-related changes in the blood-brain barrier transport processes have been identified. These include reduced hexose and butyr ate transport, reduced choline transport, reduced triiodothyronine tra nsport without a change in the transport of neutral and basic amino ac ids. The potential mechanisms underlying these age-related changes inc lude hemodynamic alterations in the cerebral circulation of aged rats, notably increased occurrence of arteriovenous shunting. Additional ag e-related changes in cerebral microvessels include alterations in prot ein composition, and increased accumulation of lipid peroxidation bypr oducts, along with changes in membrane fluidity of isolated cerebral m icrovessels. In addition, neurotransmitter activity notably beta adren ergic neurotransmission, is significantly reduced in cerebral microves sels of aged rats. These alterations taken together may account for so me of the age-related changes in the blood-brain barrier.