Autoradiographic localization and characterization of natriuretic peptide binding sites in the rat central nervous system

Atrial natriuretic factor (ANF), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are members of a family of natriuretic peptides that may be involved, among other functions, in the maintenance of proper fluid and electrolyte balance and blood pressure control, as both circulating hormones and neuropeptides. The studies presented in this thesis were undertaken primarily to provide a deeper insight into the mechanisms of action of natriuretic peptides on the central nervous system (CNS). Using autoradiographic and cross-linking techniques, the precise cellular localization, specificity, and subtypes of natriuretic peptide binding sites in selected areas of the rat CNS were established. ANF binding sites are evident primarily on the basolateral plasmalemma of the epithelial cells in the choroid plexus and on plasmalemma of axons, dendrites, and astrocytes in the areas postrema. This cellular localization is consistent with the notion that circulating natriuretic peptides may exerts their effects via a CNS locus. Furthermore, evidence is provided that ANF binding sites are not only specific to ANF, but also to BNP, whereas CNP exhibits a distinct receptor selectivity. Finally, these studies provide a regional localization of three subtypes of natriuretic peptide receptor. In contrast to binding sites with characteristics of natriuretic peptide receptors A and B, which are detected in a number of CNS areas, natriuretic peptide receptor C is detected in only a few CNS structures. These studies are expected to contribute to a better understanding of the mechanism of natriuretic peptides action on the CNS