ELECTROPHYSIOLOGY OF THE CIRCUMVENTRICULAR ORGANS

Since the first anatomical description of the circumventricular organs (CVOs) as a structurally distinct group of regions in the central ner vous system (CNS), considerable information has implicated these struc tures as physiologically significant autonomic control centers located at the blood-brain interface. Specialized features of these structure s, such as their extensive vasculature, lack of the normal blood-brain barrier (BBB) (i.e., capillaries have a fenestrated endothelium), and dense aggregations of a variety of peptidergic receptors, support an involvement of the CVOs in communication between the circulation and t he CNS. The two best understood examples of CVOs with the ability to s ense circulating substances impermeable to the BBB are the subfornical organ (SFO) and the area postrema (AP). Specifically, the ability of numerous peptides to influence CNS function, as the result of actions on the neural substrate of these structures has been especially well d ocumented. Considerable anatomical, biochemical, pharmacological, and physiological evidence has implicated these structures as CNS sites at which angiotensin (ANG), atrial natriuretic peptide (ANP), vasopressi n (VP), and endothelin (ET) act to influence neuroendocrine and other more classical autonomic functions. In the following sections, we revi ew neurophysiological studies which have provided new and exciting ins ights regarding the specific neural pathways and cellular mechanisms t hrough which CVO neurons are able to exert their profound influences o ver central autonomic control. (C) 1996 Academic Press, Inc.