Pflügers Archiv

, Volume 344, Issue 4, pp 327–337 | Cite as

Effects of exposure to hot environments on total and regional blood flow in the brain and spinal cord of the sheep

  • J. R. S. Hales


In conscious adult sheep, normal blood flow rate (ml 100 g−1 min−1) differed markedly in different regions of the brain and spinal cord. In mild heat stress there was no significant change in total or regional blood flow in the brain or spinal cord. In severe heat stress body temperature increased at a rate of approximately 2°C per hour, until a total change of approximately 2.4°C had occurred. Vigorous panting resulted in severe respiratory alkalosis. Brain and spinal cord blood flow declined to approximately 70% of control levels, the change being greatest in the pons and medulla oblongata and least in the cerebellum. It is suggested that a much greater fall in blood flow was prevented by a stimulatory effect of increased body temperature counteracting depressant effects of hypocapnia and possibly other factors. There does not appear to be any blood flow through arteriovenous anastomoses in the brain. Oxygen consumption by the cerebral hemispheres either remained unchanged or decreased slightly.

Key words

Brain Blood Flow Brain Oxygen Consumption Brain AVA's Hyperthermia Sheep Brain 


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  1. 1.
    Alexander, G., Bell, A. W., Hales, J. R. S.: Effect of cold exposure on tissue blood flow in the new-born lamb. J. Physiol. (Lond.)234, 65–77 (1973).Google Scholar
  2. 2.
    Colton, J. S., Frankel, H. M.: Cerebrovascular response to CO2 during hyperthermia. Amer. J. Physiol.223, 1041–1043 (1972)Google Scholar
  3. 3.
    Cranston, W. I., Rosendorff, C.: Local blood flow, cerebrovascular autoregulation and CO2 responsiveness in the rabbit hypothalamus. J. Physiol. (Lond.)215, 577–590 (1971)Google Scholar
  4. 4.
    Dawes, J. D. K., Prichard, M. M. L.: Studies of the vascular arrangements of the nose. J. Anat. (Lond.)87, 311–322 (1953)Google Scholar
  5. 5.
    Demers, Von H. G., Spaich, P., Usinger, W.: Der Hirnkreislauf bei erhöhter Körpertemperatur. Verh. dtsch. Ges. Kreisl.-Forsch.35, 340–343 (1969)Google Scholar
  6. 6.
    Forrester, A. C., McDowall, D. G., Harper, A. M., Nisbet, H. I. A.: Cerebral blood flow during hypothermia with control of arterial carbon dioxide tension. Proc. 3 rd World Congr. on Anaes., Brazil 1964, pp. 129–134 (1964)Google Scholar
  7. 7.
    Forsyth, R. P., Hoffbrand, B. I.: Redistribution of cardiac output after sodium pentobarbital anesthesia in the monkey. Amer. J. Physiol.218, 214–217 (1970)Google Scholar
  8. 8.
    Forsyth, R. P., Nies, A. S., Wyler, F., Neutze J. Kelmon, K. L.: Normal distribution of cardiac output in the unanesthetized, restrained rhesus monkey. J. appl. Physiol.25, 736–741 (1968)Google Scholar
  9. 9.
    Fujishima, M., Scheinberg, P., Busto, R.: Cerebral cortical blood flow. Variable effects of hypoxia in the dog. Arch. Neurol. (Chic.)25, 160–167 (1971)Google Scholar
  10. 10.
    Hales, J. R. S.: Determination of the effect of climatic stress on regional brain and spinal cord blood flow, using radioactive microspheres. Proc. Aust. physiol. pharmacol. Soc.2, No. 1, 45–46 (1971)Google Scholar
  11. 11.
    Hales, J. R. S.: Chronic catheterization for sampling venous blood from the brain of the sheep. Pflügers Arch.337, 81–85 (1972)Google Scholar
  12. 12.
    Hales, J. R. S.: Physiological responses to heat. In: MTP international review of science, Physiology Series 1, vol. 7, pp. 107–162, Ed. D. Robertshaw. London: Butterworths 1973Google Scholar
  13. 13.
    Hales, J. R. S.: Radioactive microsphere measurement of cardiac output and regional tissue blood flow in the sheep. Pflügers Arch.344, 119–132 (1973)Google Scholar
  14. 14.
    Hales, J. R. S.: Effects of exposure to hot environments on the regional distribution of blood flow and on cardiorespiratory function in sheep. Pflügers Arch.344, 133–148 (1973)Google Scholar
  15. 15.
    Hales, J. R. S., Brown, B. W., Mattner, P. E.: Blood flow in brain, liver, fat and muscle, measured by microsphere and iodoantipyrine techniques. Int. Res. Commun. Syst.1, No. 11-1-4 (1973)Google Scholar
  16. 16.
    Hales, J. R. S., Findlay, J. D.: Respiration in the ox: Normal values and the effects of exposure to hot environments. Resp. Physiol.4, 333–352 (1968)Google Scholar
  17. 17.
    Harper, A. M.: The inter-relationship between aPCOM2 and blood pressure in the regulation of blood flow through the cerebral cortex. Acta neurol. scand.41, (Suppl. 14), 94–103 (1965)Google Scholar
  18. 18.
    Harper, A. M., Glass, H. I.: Effect of alterations in the arterial carbon dioxide tension on the blood flow through the cerebral cortex at normal and low arterial blood pressure. J. Neurol. Neurosurg. Psychiat.28, 449–452 (1965)Google Scholar
  19. 19.
    Heyman, A., Patterson, J. L., Nichols, F. T.: The effects of induced fever on cerebral functions in neurosyphilis. J. clin. Invest.29, 1335–1341 (1950)Google Scholar
  20. 20.
    Iriki, M., Riedel, W., Simon, E.: Regional differentiation of sympathetic activity during hypothalamic heating and cooling in anesthetized rabbits. Pflügers Arch.328, 320–331 (1971)Google Scholar
  21. 21.
    Kennady, J. C., Taplin, G. V.: Shunting in cerebral microcirculation. Amer. Surg.33, 763–771 (1967)Google Scholar
  22. 22.
    King, B. D., Sokoloff, L., Wechsler, R. L.: The effect of l-epinephrine and l-norepinephrine upon cerebral circulation and metabolism in man. J. clin. Invest.31, 273–279 (1952)Google Scholar
  23. 23.
    Klosovskii, B. N.: Blood circulation in the brain. Jerusalem: Israel Program for Scientific Translations (1963)Google Scholar
  24. 24.
    Landau, W. M., Freygang, W. H., Roland, L. P., Sokoloff, L., Kety, S. S.: The local circulation of the living brain; values in the unanesthetized and anesthetized cat. Trans. Amer. neurol. Ass.80, 125–129 (1955)Google Scholar
  25. 25.
    Lassen, N. A., Feinberg, I., Lane, M. H.: Bilateral studies of cerebral oxygen uptake in young and aged normal subjects and in patients with organic dementia. J. clin. Invest.39, 491–500 (1960)Google Scholar
  26. 26.
    Nemoto, E. M., Frankel, H. M.: Cerebrovascular response during progressive hyperthermia in dogs. Amer. J. Physiol.218, 1060–1064 (1970)Google Scholar
  27. 27.
    Nemoto, E. M., Frankel, H. M.: Cerebral oxygenation and metabolism during progressive hyperthermia. Amer. J. Physiol.219, 1784–1788 (1970)Google Scholar
  28. 28.
    Neutze, J. M., Wyler, F., Rudolph, A. M.: Use of radioactive miscrospheres to assess distribution of cardiac output in rabbits. Amer. J. Physiol.215, 486–495 (1968)Google Scholar
  29. 29.
    Olesen, J.: The effect of intra-carotid epinephrine, norepinephrine and angiotensin on the regional cerebral blood flow in man. Neurology (Minneap.)22, 978–987 (1972)Google Scholar
  30. 30.
    Ranson, S. W., Clark, S. L.: The anatomy of the nervous system. Philadelphia-London: W. B. Saunders Co. 1947Google Scholar
  31. 31.
    Robertshaw, D., Whittow, G. C.: The effect of hyperthermia and localized heating of the anterior hypothalamus on the sympathoadrenal system of the ox (Bos taurus). J. Physiol. (Lond.)187, 351–360 (1966)Google Scholar
  32. 32.
    Rosomoff, H. L., Holaday, D. A.: Cerebral blood flow and cerebral oxygen consumption during hypothermia. Amer. J. Physiol.179, 85–88 (1954)Google Scholar
  33. 33.
    Roth, J. A., Greenfield, A. J., Kaihara, S., Wagner, H. N.: Total and regional cerebral blood flow in unanesthetized dogs. Amer. J. Physiol.219, 96–101 (1970)Google Scholar
  34. 34.
    Rudolph, A. M., Heymann, M. A.: The circulation of the foetus in utero. Methods for studying distribution of blood flow, cardiac output and organ blood flow. Circulat. Res.21, 163–184 (1967)Google Scholar
  35. 35.
    Smith, A. L., Pender, J. W., Alexander, S. C.: Effects of PCO 2 on spinal cord blood flow. Amer. J. Physiol.216, 1158–1163 (1969)Google Scholar
  36. 36.
    Tschetter, T. H., Klassen, A. C., Resch, J. R.: Regional cerebral blood flow in dogs using a particle-distribution method. Proc. Soc. exp. Biol. Med. (N.Y.)131, 1244–1249 (1969)Google Scholar

Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • J. R. S. Hales
    • 1
  1. 1.Division of Animal Physiology, Ian Clunies Ross Animal Research Laboratory, ProspectC.S.I.R.O.Australia

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