Effects of changes of blood pressure, respiratory acidosis and hypoxia on blood flow in the sciatic nerve of the rat.

Abstract

SUMMARY1. Using the hydrogen clearance technique, we have measured blood flow in the sciatic nerves of healthy, anaesthetized rats at rest, at various arterial blood pressures, and during respiratory acidosis and hypoxia.-2. The majority of hydrogen clearance curves were bi-exponeiiinil. The slower component appears to reflect nerve blood flow more accurately than either the fast component or the composite value obtained from both components. 3. Mean nerve blood flow estimated from the slow component of the seventeen bi-exponential hydrogen clearance curves and from the seven mono-exponential curves was 15-8+ 1 1 ml min-100 g-1 (±S.E. of the mean). The mean value of the fast component of the bi-exponential curves was 118+ 6 ml min-100 g-' and that obtained from both components was 25-9 + 2-6 ml min-100 g-1.4. Sciatic nerve blood flow was measured over a range of arterial blood pressures of 60-160 mmHg. There is a curvilinear relationship between pressure and flow suggesting that the nerve vascular bed responds passively to changes in perfusion pressure.5. Respiratory acidosis resulted in no significant change in nerve blood flow. The mean flow was 15-5+ 1-9 ml min-100 g'l. During hypoxia, nerve blood flow decreased to 7-5+ 1-4 ml min' 100 g'1 as a result of a reduction in arterial blood pressure and an increase in vascular resistance. 6. These findings suggest that normal nerve blood flow is high in relation to metabolic activity, especially when compared with the brain.

Effect of the aldose reductase inhibitor fidarestat on experimental diabetic neuropathy in the rat

“…These changes are accompanied by normalisation morphometric alterations in both large and small DRG neurons in EDN. We used the H 2 -polarographic technique to measure NBF because of its ability to separate nutritive (capillary) from capacitative (arteriovenous) flow and its ability to measure NBF repeatedly under various physiological conditions [8]. Other techniques, such as 14 C-labelled iodoantipyrine require killing the animal for a single blood flow determination [21].…”

“…The following experiments were performed according to previously described methodology [8,10,20]. The rats were anaesthetised with an i.p.…”

“…pathway hyperactivity [1], myoinositol reduction [2,3], reduction in Na + , K + -ATPase activity [2,4], reduction in nerve blood flow (NBF) and oxygenation [5][6][7][8][9], reduction in nitric oxide (NO) or NO synthase (NOS) [5,10,11] and evidence of increased oxidative stress [11,12]. Recent work from several research centres has led to a more integrated and unified hypothesis on the pathogenesis of diabetic neuropathy [11,12].…”

Endoneurial blood flow in rat sciatic nerve during development.

“…The details of the procedure have been previously described (Low & Tuck, 1984). Briefly, rats were anaesthetized with Inactin (Byk Gulden, Konstanz, Germany; 100 mg kg-', i.P.…”

“…The rate of blood flow in adult mammalian sciatic nerve has been studied with H2 microelectrode polarography (Smith, Kobrine & Rizzoli, 1977;Low & Tuck, 1984), laser-Doppler flowmetry (Rundquist, Smith, Michel, Ask, Oberg & Rapoport, 1985;Takeuchi & Low, 1987), and rapidly diffusing radiotracers (Rundquist et al 1985; Sladky, Greenberg & Brown, 1985; Sugimoto, Monafo & Eliasson, 1986). The salient characteristics which emerge from these studies are: (1) even though endoneurial and sheath (epineurium and perineurium) blood flows are interconnected, the former can be measured separately; (2) endoneurial flow consists of a larger nutritive component and a smaller capacitative component; (3) there is no evidence of autoregulation of endoneurial blood flow (EBF); and (4) segmental endoneurial vasculature is nourished by axial vessels from adjoining segments and by transperineurial radial vessels arising from the sheath vasculature.…”