Blood-brain barrier: endogenous modulation by adrenal-cortical function.

The blood-brain barrier restricts the passage of molecules from the blood to the brain. The permeability of the barrier to iodine-125-labeled bovine serum albumin was examined in rats that had undergone adrenalectomy, adrenal demedullation, and corticosterone replacement. Adrenalectomy, but not adrenal demedullation, increased the permeability of brain tissue to the isotopically labeled macromolecule; corticosterone replacement reversed this effect. These results indicate that the blood-brain barrier may be hormonally regulated; that is, the pituitary-adrenal axis may physiologically modulate the permeability of the brain microvasculature to macromolecules.