Cerebral circulation: humoral regulation and effects of chronic hypertension.

New concepts have emerged in recent years concerning regulation of cerebral circulation. The purpose of this review is to summarize briefly several of these concepts. First, humoral mechanisms may have important effects on cerebral blood vessels and blood flow to choroid plexus. Recent evidence suggests that several vasoactive peptides may have major effects on fluid and ion balance in the brain by altering blood flow to the choroid plexus and possibly the production of cerebrospinal fluid. Second, chronic hypertension produces structural remodeling and hypertrophy of cerebral blood vessels and a shift in the relationship of cerebral blood flow to systemic blood pressure. Third, endothelium-dependent responses of cerebral arterioles to receptor and nonreceptor mediated agonists are impaired during chronic hypertension. Alterations in endothelium-dependent responses of cerebral arterioles during chronic hypertension appears to be due to release of an endothelium-derived contracting factor.