Interdependency of local capillary density, blood flow, and metabolism in rat brains

Abstract

Previous investigations have established a strong correlation between local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU). In the present study the relationship between density of perfused brain capillaries and LCBF or LCGU was investigated in conscious and anesthetized rats. Perfused capillaries were stained by labeling the plasma with the gamma globulin-coupled fluorochromes, fluorescein isothiocyanate (FITC) and lissamine-rhodamine B 200 (RB 200). The density of perfused capillaries was determined in 12 different brain structures by fluorescence microscopy of embedded brain sections following coronal sectioning in a cryostat. Significant differences were found among brain structures investigated; the lowest density of perfused capillaries was found in the white matter (e.g., corpus callosum 162 fragments/mm2), whereas the highest values were determined in the structures of the auditory system (e.g., inferior colliculus 810 fragments/mm2). LCBF and LCGU were measured in two separate groups of rats using standard autoradiographic methods. In all three experimental groups, the same structures were identified and measured with a high degree of accuracy and local resolution. Density of perfused capillaries correlated well with LCBF (r = 0.93) and even better with LCGU (r = 0.97). In addition to the relationship between LCGU and LCBF established by earlier studies, these data show the intimate interrelationship between LCGU, density of perfused capillaries, and LCBF.

Microvessel density estimation in the human brain by means of dynamic contrast‐enhanced echo‐planar imaging

“…As indicated in Table 2, our MVD estimates are comparable to histologic values for rat brain given by Klein and coworkers (19). Moreover, assuming that the rat brain histologic data provide a reasonable approximation for humans, our data imply that N U may be the better estimator of the MVD, as also suggested by Eq.…”

“…Combining Eq. [18] with the expression (6) ⌬R* 2 Ϸ 4 3 f␥B 0 ⌬ , [19] then gives the criterion 3⌬R* 2 4 f␥B 0 0 Ͼ Ͼ1. [20] Here B 0 is the magnitude of the main field, and ␥ ϭ 2.675 ϫ 10 8 s -1 /T is the proton gyromagnetic ratio.…”

Functional neuroimaging of normal human sleep by positron emission tomography

“…On top of these local processes, CBF is also regulated by general factors such as perfusion pressure (autoregulation; Paulson et al 1990), PCO 2 and PO 2 and possibly a neurogenic tone (Lou et al 1987). A local static factor such as capillary density is also functionally related to rCBF: the higher the capillary density, the higher the rCBF (Klein et al 1986;Borowsky and Collins 1989;Kuchinsky 1997). During cerebral activation, there is a transient uncoupling between the local metabolic rates for oxygen (CMRO 2 ) and rCBF.…”

Simulation study of brain blood flow regulation by intra-cortical arterioles in an anatomically accurate large human vascular network: Part I: Methodology and baseline flow

“…In particular, regional differences in BOLD reactivity between rest (baseline) and active neuronal states, for example between primary and association cortex, have been observed (Ances et al, 2008) but are poorly understood. Regional differences in the baseline cerebral blood flow (CBF) have also been observed (Klein et al, 1986), as well as regional differences in CBF and BOLD reactivity when hemodynamic variations independent of neural activity are induced (e.g. by hypercapnia, acetazolamide) (Davis et al, 1998;Rostrup et al, 2000;Ances et al, 2008).…”