Hormonal influence on water permeability across the blood-brain barrier.

We have shown that steroid manipulations may influence the rate of flux of water across the blood-brain barrier. Such changes are regionally variable and are best seen in the cerebral cortex. Administration of dexamethasone produced decreased water permeability while withdrawal of dexamethasone and ethinyloestradiol resulted in increased permeability. Increased water content in cerebral cortex was demonstrated after steroid withdrawal and ethinyloestradiol administration. We believe that these experimental findings may have relevance in the clinical situation and may help in understanding the pathogenesis of some types of brain oedema. One such example is benign intracranial hypertension where brain swelling is seen typically in young obese females and is also associated with the contraceptive pill, pregnancy and corticosteroid withdrawal.