Pflügers Archiv

, Volume 338, Issue 4, pp 335–346 | Cite as

Influence of hypothermia at different arterial CO2 pressures and local cooling of the spinal cervical cord on the activity of single phrenic motoneurons

  • K. H. Bock
  • W. Kindermann
  • K. Pleschka
Article

Summary

The discharges of single phrenic units were examined in anesthetized, paralyzed, vagotomized and artificially ventilated dogs during hypothermia and during local cooling of the cervical spinal cord. The following results were obtained for individual phrenic motoneurons during hypothermia. The average frequency of impulses during discharge decreased with decreasing blood temperature. This effect was in principle independent of the arterial CO2 pressure (PaCO2). In some animals recruitment of additional units occurred with falling blood temperature. The response of phrenic units to CO2 stimulation was qualitatively identical at normal and at decreased blood temperatures, but was less pronounced during hypothermia. However, the thresholds of activation by PaCO2 of single phrenic motoneurons were lowered by hypothermia. The results suggest that the observed changes of phrenic motoneuron responses induced by hypothermia are caused by temperature effects on the respiratory output at both the central and the spinal level. An inhibitory influence of lowered blood temperature on the respiratory center is indicated by the reduced response to CO2 stimulation. On the other hand, the recruitment of motor units during hypothermia suggests a stimulating effect of cold on the phrenic motoneurons. The reduced discharge frequency of the single units during hypothermia may be ascribed to effects at the central and spinal levels.

The effects of cold at the spinal level on the discharges of single phrenic units were evaluated by local cooling of the cervical spinal cord by about 4°C. During the experiments body temperature and PaCO2 were kept at normal levels. The results indicate that the frequency of the bursts of phrenic nerve discharge, which is equivalent to respiratory frequency, remained constant. The average impulse frequency within the single burst decreased significantly. Recruitment of additional units was frequently observed. It is suggested that the observed effects of local spinal cooling on phrenic nerve discharge are caused by a prolongation of the excitatory and inhibitory synaptic processes.

Key words

Phrenic Motoneurons Hypothermia CO2 Stimulus Local Spinal Cooling Respiratory Control 

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References

  1. Adrian, E. D., Bronk, D. W.: The discharge of impulses in motor nerve fibres. Part I. Impulses in single fibres of the phrenic nerve. J. Physiol. (Lond.)66, 81–101 (1928).Google Scholar
  2. Brendel, W.: Die Bedeutung der Hirntemperatur für die Kältegegenregulation. I. Der Einfluß der Hirntemperatur auf den respiratorischen Stoffwechsel des Hundes in thermoindifferenter Umgebung. Pflügers Arch. ges. Physiol.270, 607–627 (1960).Google Scholar
  3. Dittler, R.: Über die funktionelle Verknüpfung der Atemzentren und das Verhalten der Zwerchfellaktionsströme bei zentraler Kühlung. Zbl. Physiol.26, 1175–1178 (1913).Google Scholar
  4. Dittler, R., Garten, S.: Die zeitliche Folge der Aktionsströme in Phrenicus und Zwerchfell bei der natürlichen Innervation. Z. Biol.58, 420–450 (1912).Google Scholar
  5. Gesell, R., Atkinson, A. K., Brown, R. C.: The gradation of intensity of inspiratory contractions. Amer. J. Physiol.131, 659–673 (1941).Google Scholar
  6. Gill, P. K.: The effects of end-tidal CO2 on the discharge of individual phrenic motoneurones. J. Physiol. (Lond.)168, 239–257 (1963).Google Scholar
  7. Gill, P. K., Kuno, M.: Properties of phrenic motoneurones. J. Physiol. (Lond.)168, 258–273 (1963a).Google Scholar
  8. Gill, P. K., Kuno, M.: Excitatory and inhibitory actions on phrenic motoneurones. J. Physiol. (Lond.)168, 274–289 (1963b).Google Scholar
  9. Golovin, A. P.: Changes in respiration and arterial pressure produced by the perperfusion of a cold fluid through the cerebral ventricles. In: P. M. Starkov: The problem of acute hypothermia, p. 53. London: Pergamon Press 1960.Google Scholar
  10. Hess, R.: Untersuchungen über das Ursprungsgebiet des primären Atmungsrhythmus. Pflügers Arch. ges. Physiol.243, 259–282 (1940).Google Scholar
  11. Higashi, K.: Experimental studies on the cooling irrigation of cerebral ventricular system. Arch. Jap. Chir.26, 624 (1957).Google Scholar
  12. Klussmann, F. W.: Der Einfluß der Temperatur auf die afferente und efferente motorische Innervation des Rückenmarks. I. Temperaturabhängigkeit der afferenten und efferenten Spontantätigkeit. Pflügers Arch.305, 295–315 (1969).Google Scholar
  13. Koizumi, K.: Tetanus and hyperresponsiveness of the mammalian spinal cord produced by strychnine, guanidine and cold. Amer. J. Physiol.183, 35–43 (1955).Google Scholar
  14. Kosaka, M., Simon, E., Thauer, R., Walther, O. E.: Effect of thermal stimulation of spinal cord on respiratory and cortical activity. Amer. J. Physiol.217, 858–863 (1969).Google Scholar
  15. Mitchell, R. A., Loeschcke, H. H., Severinghaus, J. W., Richardson, B. W., Massion, W. H.: Regions of respiratory chemosensitivity on the surface of the medulla. Ann. N.Y. Acad. Sci.109, 661–681 (1963).Google Scholar
  16. Nicholson, H. C.: Localization of the central respiratory mechanism as studied by local cooling of the surface of the brain stem. Amer. J. Physiol.115, 402–409 (1936).Google Scholar
  17. Nicholson, H. C., Brezin, D.: Alteration of the actions of various respiratory modifiers by local cooling of the floor of the 4th ventricle. Amer. J. Physiol.118, 441–451 (1937).Google Scholar
  18. Nunn, J. F., Bergman, N. A., Bunatyan, A., Coleman, A. J.: Temperature coefficients for PCO2 and PO2 of blood in vitro. J. appl. Physiol.20, 23–26 (1965).Google Scholar
  19. Pierau, F. K., Klee, M. R., Klussmann, F. W.: Effects of local hypo- and hyperthermia on mammalian spinal motoneurones. Fed. Proc.28, 1006–1010 (1969).Google Scholar
  20. Pierau, F. K., Klussmann, F. W.: Spinal excitation and inhibition during local spinal cooling and warming. J. Physiol. (Paris)63, 380–382 (1971).Google Scholar
  21. Pitts, R. F.: Excitation and inhibition of phrenic motor neurones. J. Neurophysiol.5, 75–88 (1942a).Google Scholar
  22. Pitts, R. F.: The basis of repetitive activity in phrenic motoneurones. J. Neurophysiol.6, 439–454 (1943).Google Scholar
  23. Pleschka, K.: Der Einfluß der Temperatur auf die elektrische Aktivität des Nervus phrenicus. Untersuchungen am aufgeschnittenen Regelkreis. I. Hypothermine. Pflügers Arch.308, 333–356 (1969).Google Scholar
  24. Pleschka, K., Albers, C., Heerd, E.: Der Einfluß der Temperatur auf die CO2-Schwelle des Atemzentrums. Pflügers Arch. ges. Physiol.286, 142–158 (1965).Google Scholar
  25. Rau, B.: Der Einfluß der Rückenmarkstemperatur auf die Entladungsfrequenz und die recurrente Hemmung tonischer Motoneurone. Inaugural-Dissertation, Gießen 1970.Google Scholar
  26. Rosenthal, T. B.: The effect of temperature on the pH of blood and plasma in vitro. J. biol. Chem.173, 25–30 (1948).Google Scholar
  27. Schläfke, M., Loeschke, H. H.: Lokalisation eines an der Regulation von Atmung und Kreislauf beteiligten Gebietes an der ventralen Oberfläche der Medulla oblongata durch Kälteblockade. Pflügers Arch. ges. Physiol.297, 201–220 (1967).Google Scholar

Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • K. H. Bock
    • 1
  • W. Kindermann
    • 1
  • K. Pleschka
    • 1
  1. 1.W. G. Kerckhoff-Institut der Max-Planck-GesellschaftBad Nauheim

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