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

• Published in: Journal of comparative neurology (1911) Vol. 306; no. 1; p. 83
• Main Authors: Gross, P M, Wall, K M, Wainman, D S, Shaver, S W
• Format: Journal Article
• Language: English
• Published: United States 01-04-1991
• Subjects: Animals; Capillaries - anatomy & histology; Capillaries - physiology; Consciousness; Glucose - metabolism; Male; Medulla Oblongata - blood supply; Medulla Oblongata - metabolism; Medulla Oblongata - physiology; Rats - anatomy & histology; Rats - physiology; Rats, Inbred Strains; Regional Blood Flow; Vagus Nerve - physiology
• ISSN: 0021-9967
• DOI: 10.1002/cne.903060107

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), plasma flow, and tissue glucose metabolism (range of 0.48-0.71 mumol.g-1.min-1) were linearly related in the dorsal vagal complex. The most striking quantitative difference among structures in this brain region were the rates of transcapillary influx and derived permeability X surface area (PS) products of [14C]AIB, which has physicochemical properties resembling those of hormones. PS products for AIB were negligible in most medullary gray matter regions (less than 1 microliter.g-1.min-1, indicative of blood-brain barrier properties), but were 20-59X and 99-402X higher in NTS subnuclei and area postrema, respectively. An extraordinary feature of the microcirculation in area postrema was the long-duration transit of tracer sucrose and blood, a characteristic that would amplify the sensing ability of area postrema as it monitors the composition of the circulation.