The microcirculation of rat circumventricular organs and pituitary gland

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Abstract

Blood volume, blood flow, and blood-to-tissue transfer of an amino acid in circumventricular organs, such as the median eminence and subfornical organ, and the pituitary gland of conscious rats were measured by using quantitative autoradiographic techniques and computerassisted processing of the tissue images. Retained erythrocyte and plasma volumes observed in circumventricular organs and the anterior and neural lobes of the pituitary gland were dissimilar but in all cases greater by several times than those in cerebral grey matter; these findings suggest the presence of a dense network of high-resistance microvessels in circumventricular organs. The rate of capillary blood flow in the subfornical organ and median eminence was similar to that of grey matter, whereas blood flow in the pituitary neural lobe was several times higher than in grey matter. Thus the apparent velocity of intracapillary blood flow is much higher in the neural lobe than in the subfornical organ. Blood-to-tissue transfer of a small neutral amino acid, alpha-aminoisobutyric acid, was 200 to 700 times more rapid in circumventricular organs and pituitary neural lobe than in the inferior colliculus and caudate nucleus, structures having a blood-brain barrier (BBB). Morphometric analyses indicated that capillary volume and surface area were two times larger in the neural lobe than in the subfornical organ. Moreover, capillaries of the neural lobe and subfornical organ had numerous endothelial fenestrations and cytoplasmic pits or vesicles, whereas capillaries of the inferior colliculus had no fenestrations and fewer vesicles. These studies demonstrate quantitative differences in the microcirculatory systems not only between circumventricular organs and BBB structures but also among circumventricular organs.

References (37)

  • M. Castel et al.

    The movement of lanthanum across diffusion barriers in choroid plexus of the cat

    Brain Res

    (1974)
  • P.M. Gross

    The subfornical organ as a model of neurohumoral integration

    Brain Res Bull

    (1985)
  • W.P. Koella et al.

    Extra-blood-brain-barrier structures

    nt Rev Neurobiol

    (1967)
  • I.G. Akmayev

    Morphological aspects of the hypothalamichypophyseal system III. Vascularity of the hypothalamus, with special reference to its quantitative aspects

    Z Zellforsch

    (1971)
  • T. Bär

    The Vascular System of the Cerebral Cortex

    (1980)
  • R.G. Blasberg et al.

    Transport of alpha-aminoisobutyric acid across brain capillary and cellular membranes

    J Cereb Blood Flow Metab

    (1983)
  • R. Blasberg et al.

    Concurrent measurements of blood flow and transcapillary transport in avian sarcoma virus-induced experimental brain tumors: implications for chemotherapy

    J Pharmacol Exp Ther

    (1984)
  • M.W.B. Bradbury

    The Concept of a Blood-Brain Barrier

    (1979)
  • K.R. Brizzee

    A comparison of cell structure in the area postrema, supraoptic crest, and intercolumnar tubercle with notes on the neurohypophysis and pineal body in

    J Comp Neurol

    (1954)
  • R.D. Broadwell et al.

    Entry of peroxidase into neurons of the central nervous system from extracerebral and cerebral blood

    J Comp Neurol

    (1976)
  • K.L. Bruning et al.
  • J.F. Christ

    Nerve supply, blood supply and cytology of the neurohypophysis

  • J.E. Cremer et al.

    Relationship between extraction and metabolism of glucose, blood flow, and tissue blood volume in regions of rat brain

    J Cereb Blood Flow Metab

    (1983)
  • E.W. Dempsey et al.

    An electron microscopic study of the blood-brain barrier in the rat, employing silver nitrate as a vital stain

    J Biaphys Biochem Cytol

    (1955)
  • A. Ermisch et al.

    Blood-brain barrier and peptides

    J Cereb Blood Flow Metab

    (1985)
  • J.D. Fenstermacher et al.

    Blood-brain barrier

  • J.T. Fitzsimons

    The Physiology of Thirst and Sodium Appetite

  • C. Goochee et al.

    Application of computer-assisted image processing to autoradiographic methods for studying brain functions

    Trends Neurosci

    (1984)
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