Parallel changes of blood flow and heterogeneity of capillary
plasma perfusion in rat brains during hypocapnia.
Vogel, Johannes, Roger Abounader, Helmut Schr[diaeresis]ock, Karin
Zeller, Roman Duelli, and Wolfgang Kuschinsky.
Department of Physiology, University of Heidelberg, Heidelberg,
Germany
APStracts 2:0505H, 1995.
Plasma perfusion patterns were investigated in brain capillaries
during decreased ce rebral blood flow induced by hyperventilation.
Anesthetized rats were decapitated 3-4 seconds after an i.v. bolus
injection of Evans blue. The measured steep increase of the arterial
dye concentration at this moment ensures that different capillary
plasma transit times are reflected in different intracapillary dye
concentrations. The observed heterogeneity of capillary plasma
transit time was expressed as coefficient of varia tion (SD/mean) of
the intracapillary dye concentrations. For comparison, cerebral blood
flow was determined at comparable pCO2 values in a second
experimental group. At arterial pCO2 values between 40 and 25 mmHg
the cerebral blood flow and the coefficient of variation of the
intracapillary dye concentration decreased with decreasing pCO2
whereas at pCO2 values below 25 mmHg cerebral blood flow and
coefficient of variation did not correlate with the arterial pCO2.
However, it cannot be excluded that the coefficient of variation of
the intracapillary dye concentration increases between 25 and 14 mmHg
and decreases between 14 and 10 mmHg. It is concluded that the
reduction of cerebral blood flow measured during moderate hypocapnia
is paralleled by a decreased heterogeneity of the brain capillary
perfu sion. During severe hypocapnia this relationship is lost
indicating a potential distur bance of the cerebral microcirculation.
Received 22 June 1995; accepted in final form 1 November 1995.
APS Manuscript Number H572-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95