Regional response of cerebral blood volume to graded hypoxic hypoxia in rat brain

Abstract

These findings imply that hypoxic hypoxia significantly raises CBV in different brain areas, in proportion to the severity of the insult. These results support the notion that the vasodilatory effect of hypoxia is deleterious in patients with reduced intracranial compliance.

Assessment of vascular reactivity in rat brain glioma by measuring regional blood volume during graded hypoxic hypoxia

“…Considering that pixels with high BV (i.e., BV413.3 ml.100g-1) were excluded (see Materials and Methods section), the present changes in BV in the contralateral tissue should involve parenchymal arterioles and venules. The BV response to hypoxic hypoxia in this region ( þ 28714% of control value at FiO 2 of 0.12) was close to that reported in normal rats ( þ 38725%) (Julien-Dolbec et al, 2002). In brain tumour, there is a large heterogeneity in vessel morphology (number, size, connections).…”

“…However, our control values of BV in the contralateral region (2.270.6 ml.100 g À1 ) were notably smaller than those found in normal rat striatum using the same technique (3.170.7 ml.100 g À1 ) (Julien-Dolbec et al, 2002). Similar findings concerning local cerebral blood flow were noted between normal rats and rats with brain glioma (Aizawa et al, 1990).…”

“…First, despite epinephrine, the highest level of hypoxic hypoxia (FiO 2 of 0.10) was associated with hypocapnia and with a decrease in MABP, which a priori, might interfere with BV changes. However, as discussed elsewhere (Julien-Dolbec et al, 2002), the influence of these two parameters on BV changes is likely minor compared to that of severe hypoxia hypoxia, and should not invalid the comparison between regions of the response to hypoxia. Second, the relationship between DR 2 * and BV postulates that the contrast agent must be confined within the vascular space.…”

“…One way to explore the cerebrovascular reactivity is to measure blood volume (BV) response to hypoxic hypoxia (low PaO2), which is a potent vasodilator in brain (Kontos et al, 1978). We recently measured regional cerebral BV response to hypoxic hypoxia in normal rats, using susceptibility contrast magnetic resonance imaging (MRI) (Julien-Dolbec et al, 2002). By measuring BV response to hypoxic hypoxia in a model of rat brain glioma, our goal was to assess overall vessel reactivity to hypoxia in those tumours and to determine possible differences in responsiveness between intratumoral, peritumoral and nontumoral areas.…”

Cerebral blood flow and BOLD fMRI responses to hypoxia in awake and anesthetized rats

“…A hypoxia-induced CBF increase of ~80% (measured using butanol indicatorfractionation method) was reported in choral hydrate-anesthetized rats with an arterial pO 2 of 49 mm Hg (Shockley and LaManna, 1988). A hypoxia-induced CBF increase was reported in mechanically ventilated animals that were anesthetized with thiopental (Julien-Dolber et al, 2002). These differences in findings could be due to the use of different anesthetics, the duration of hypoxic exposure, or other methodological details.…”