Project Details


Cerebral 02 delivery is controlled by both cerebral blood flow and
the number of perfused capillaries. Control of the number of
perfused cerebral capillaries, in contrast to cerebral blood flow,
has not been extensively studied under 02 supply-limited
conditions. From our previous work, we know that only about half
of the available cerebral capillaries are perfused at rest and this
reserve can be utilized during 02 supply stress. Both central and
peripheral adrenergic neurons can alter cerebral 02 delivery.
Their influence on cerebral 02 delivery appears more important
under conditions of 02 lack. We intend to study the effects of
various means of reducing 02 supply (anemia, hypoxia, carbon
monoxide, hypocapnia) on the perfusion of cerebral capillaries and
sympathetic influence on the control of 02 delivery in conscious
rats. The primary hypothesis of this grant is: Central and
peripheral noradrenergic neurons decrease cerebral 02 delivery by
reducing alterations in diffusion distance and cerebral blood flow
during 02 supply stress. We also intent to study the relative
importance of the cerebral capillary response to 02 lack. To
perform these studies, we have developed a method to determine
perfused and total capillary density on a regional basis in
conscious rat brain. A fluorescent dye is injected to reveal the
perfused vessels. The tissue is then stained to reveal the total
network. This method, when coupled with measurements of cerebral
blood flow with iodoantipyrine and cerebral 02 extraction with
microspectrophotometry, will give a complete picture of the
cerebral response to 02 supply changes. The importance of
peripheral sympathetic innervation, central noradrenergic neurons
and the arterial chemoreceptors in the control of cerebral
capillary perfusion under conditions of reduced 02 supply will be
assessed. This will be determined in experiments involving
ablation of the cervical sympathetic ganglia and arterial
chemoreceptors. We will study the effects of blockade of central
and peripheral adrenoceptors. The importance of changes in
intercapillary distance on tissue oxygenation will also be assessed
through increases and decreases in cerebral capillary density.
Cerebral 02 supply can be controlled at both the arteriolar and
capillary level. Through study of the sympathetic nervous system's
influence on these two levels of control, we hope to gain a better
understanding of its normal control of cerebral 02 supply.
Effective start/end date4/1/893/31/92


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $131,678.00


  • Medicine(all)
  • Neuroscience(all)

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