Subregional topography of capillaries in the dorsal vagal complex of rats: II. Physiological properties

The differentiated cytoarchitecture, neurochemistry, and capillary organization of the rat dorsal vagal complex prompted this comprehensive investigation of microvascular physiology in 11 subdivisions of area postrema, 5 subnuclei of nucleus tractus solitarii (NTS), the dorsal motor nucleus of the vagus nerve, and 4 other gray matter structures in the dorsal medulla oblongata. Microvascular exchangeable volume (residual plasma volume), capillary blood and plasma flow, and unidirectional transfer constants for a tracer amino acid, [14C]alpha-aminoisobutyric acid (AIB), varied considerably among the structures analyzed. Exchangeable volume, largest in area postrema medial zones (about 29 microliters.g-1) and smallest in medullary gray matter (7-11 microliters.g-1), correlated directly with subregional densities of capillaries and rates of tissue glucose metabolism. Capillary blood flow (range of 1,430-2,147 microliters.g-1.min-1),…