The functional role of the alpha-1 adrenergic receptors in cerebral blood flow regulation

Cerebral vasculature is richly innervated by the α-1 adrenergic receptors similar to that of the peripheral vasculature. However, the functional role of the α-1adrenergic receptors in cerebral blood flow (CBF) regulation is yet to be established. The traditional thinking being that during normotension and normocapnia sympathetic neural activity does not play a significant role in CBF regulation. Reports in the past have stated that catecholamines do not penetrate the blood brain barrier (BBB) and therefore only influence cerebral vessels from outside the BBB and hence, have a limited role in CBF regulation. However, with the advent of dynamic measurement techniques, beat-to-beat CBF assessment can be done during dynamic changes in arterial blood pressure. Several studies in the recent years have reported a functional role of the α-1adrenergic receptors in CBF regulation. This review focuses on the recent developments on the role of the sympathetic nervous system, specifically that of the α-1 adrenergic receptors in CBF regulation.