Changes in arterioles, arteries, and local perfusion of the brain stem during hemorrhagic hypertension

1996 ◽  
Vol 270 (4) ◽  
pp. H1350-H1354 ◽  
Author(s):  
K. Toyoda ◽  
K. Fujii ◽  
S. Ibayashi ◽  
S. Sadoshima ◽  
M. Fujishima
Keyword(s):  
Blood Flow ◽  
Brain Stem ◽  
Basilar Artery ◽  
Doppler Flowmetry ◽  
Large Arteries ◽  
Cerebrovascular Resistance ◽  
Cranial Window ◽  
Arterial Blood ◽  
The Brain

Cerebral arterioles have been regarded as the primary sites of autoregulatory responses, whereas the role of large arteries in the cerebral autoregulation is poorly understood. The goal of this study was to determine in vivo whether the basilar artery and its primary branches act as resistance vessels under hypotensive conditions by simultaneously measuring their diameters and local brain stem blood flow with laser-Doppler flowmetry. In 10 anesthetized rats, blood flow to the brain stem was well maintained during stepwise hemorrhagic hypotension when mean arterial blood pressure fell from 116 +/- 3 to 50 mmHg and decreased gradually between 50 and 30 mmHg. Diameter of the basilar artery (n = 10) and its large branches (n = 22), measured through an open cranial window, increased by 10% from the baseline value at 50 mmHg and reached their maximum at 30 mmHg (314 +/- 9 from 244 +/- 6 mum, and 149 +/- 4 from 117 +/- 3 mum, respectively). Small branches (n = 15) dilated to a larger extent compared with the larger arteries throughout hypotension and reached the maximum at 30 mmHg (69 +/- 3 from 48 +/- 2 mum). Below 30 mmHg, there was a steep fall in blood flow and reduction in diameter of all-sized arteries. Thus small vessels contribute to reductions in cerebrovascular resistance throughout the entire autoregulatory-range in the brain stem circulation. Large arteries, such as the basilar artery and its branches, also contribute to reductions in cerebrovascular resistance around the lower limits of cerebral blood flow autoregulation and may thus play a significant role in maintaining blood flow to the brain stem during severe systemic hypotension.

Role of ATP-sensitive potassium channels in brain stem circulation during hypotension

1997 ◽  
Vol 273 (3) ◽  
pp. H1342-H1346 ◽  
Author(s):  
K. Toyoda ◽  
K. Fujii ◽  
S. Ibayashi ◽  
T. Kitazono ◽  
T. Nagao ◽  
...  
Keyword(s):  
Brain Stem ◽  
Basilar Artery ◽  
Katp Channels ◽  
Vehicle Group ◽  
Sprague Dawley ◽  
Doppler Flowmetry ◽  
Cranial Window ◽  
Sprague Dawley Rats ◽  
The Brain

The basilar artery and its branch arterioles dilate actively in response to a marked decrease in blood pressure and maintain cerebral blood flow (CBF) to the brain stem. We tested the hypothesis that ATP-sensitive potassium (KATP) channels play a role in the autoregulatory responses of the brain stem circulation in vivo. In anesthetized Sprague-Dawley rats, local CBF to the brain stem was determined with laser-Doppler flowmetry, and diameters of the basilar artery and branch arterioles were measured through a cranial window during stepwise hemorrhagic hypotension. During topical application of 10(-6) and 10(-5) mol/l of glibenclamide, a selective KATP-channel blocker, the lower limit of CBF autoregulation shifted upward to 60-75 from 30-45 mmHg in the vehicle group. Glibenclamide significantly impaired the dilator response of small arterioles (baseline diameter 45 +/- 2 microns) throughout hypotension (P < 0.03) but did not impair the dilatation of the basilar artery (247 +/- 3 microns) or large arterioles (99 +/- 4 microns). Thus KATP channels appear to play an important role in the regulation of CBF to the the brain stem during hypotension by mediating the compensatory dilatation of small arterioles. In contrast, these channels may not be a major regulator of the vascular tone of larger arteries during hypotension.

scholarly journals Attenuation and Recovery of Brain Stem Autoregulation in Spontaneously Hypertensive Rats

1998 ◽  
Vol 18 (3) ◽  
pp. 305-310 ◽  
Author(s):  
Kazunori Toyoda ◽  
Kenichiro Fujii ◽  
Setsuro Ibayashi ◽  
Takanari Kitazono ◽  
Tetsuhiko Nagao ◽  
...  
Keyword(s):  
Brain Stem ◽  
Basilar Artery ◽  
Antihypertensive Treatment ◽  
Spontaneously Hypertensive Rats ◽  
Hypertensive Rats ◽  
Doppler Flowmetry ◽  
Spontaneously Hypertensive ◽  
Large Arteries ◽  
Cranial Window ◽  
Severe Hypotension

Cerebral large arteries dilate actively around the lower limits of CBF autoregulation, mediated at least partly by nitric oxide, and maintain CBF during severe hypotension. We tested the hypothesis that this autoregulatory response of large arteries, as well as the response of arterioles, is altered in spontaneously hypertensive rats (SHR) and that the altered response reverts to normal during long-term antihypertensive treatment with cilazapril, an angiotensin-converting enzyme inhibitor. In anesthetized 6- to 7-month-old normotensive Wistar-Kyoto rats (WKY), 4- and 6- to 7-month-old SHR without antihypertensive treatment, and 6- to 7-month-old SHR treated with cilazapril for 10 weeks, local CBF to the brain stem was determined with laser—Doppler flowmetry and diameters of the basilar artery and its branches were measured through a cranial window during stepwise hemorrhagic hypotension. The lower limit of CBF autoregulation shifted upward in untreated SHR to 90 to 105 mm Hg from 30 to 45 mm Hg in WKY, and it reverted to 30 to 45 mm Hg in treated SHR. In response to severe hypotension, the basilar artery dilated by 21 ± 6% (mean ± SD) of the baseline internal diameter in WKY. The vasodilation was impaired in untreated SHR (10 ± 8% in 4-mo-old SHR and 4 ± 5% in 6- to 7-month-old SHR), and was restored to 22 ± 10% by treatment with cilazapril ( P < 0.005). Dilator responses of branch arterioles to hypotension showed similar attenuation and recovery as that of the basilar artery. The data indicate that chronic hypertension impairs the autoregulatory dilation of the basilar artery as well as branch arterioles and that antihypertensive treatment with cilazapril restores the diminished dilation toward normal.

Effect of Aging on Regulation of Brain Stem Circulation During Hypotension

1997 ◽  
Vol 17 (6) ◽  
pp. 680-685 ◽  
Author(s):  
Kazunori Toyoda ◽  
Kenichiro Fujii ◽  
Yutaka Takata ◽  
Setsuro Ibayashi ◽  
Megumi Fujikawa ◽  
...  
Keyword(s):  
Brain Stem ◽  
Basilar Artery ◽  
Aged Rats ◽  
Adult Rats ◽  
Doppler Flowmetry ◽  
Cranial Window ◽  
Large Branch ◽  
Small Branch ◽  
Age Related ◽  
The Brain

This study was designed to determine age-related changes in autoregulatory responses of the brain stem circulation in vivo. In anesthetized adult (4 to 6 months, n = 8) and aged (24 to 26 months, n = 7) Sprague-Dawley rats, local CBF to the brain stem was determined with laser-Doppler flowmetry and diameters of the basilar artery and its branches were measured through an open cranial window during stepwise hemorrhagic hypotension. In aged rats, the lower limit of CBF auto-regulation shifted upward to 60 to 75 mm Hg from 30 to 45 mm Hg in adult rats. Dilator responses of the basilar artery (baseline diameter: 254 ± 15 μm), large branch (109 ± 23 μm), and small branch (44 ± 10 μm) to hypotension were much smaller in aged rats than in adult rats. The maximum change in diameter of the basilar artery during profound hypotension was significantly smaller in aged rats (11 ± 8%) than that in adult ones (23 ± 12%, P < 0.05); that of the large branch was 12 ± 8% versus 33 ± 17% ( P < 0.005); and that of the small branch was 17 ± 7% versus 40 ± 13% ( P < 0.0005), suggesting greater attenuation of the responses in the smaller vessels. Thus, this study provides direct evidence that aging diminishes the compensatory dilatation of brain stem arterioles and arteries during hypotension and modifies the autoregulatory plateau of CBF, which seems to increase the risk of the brain stem ischemia during hypotensive conditions.

Regional blood flow in the brain and spinal cord of hypothermic rats

1989 ◽  
Vol 257 (3) ◽  
pp. H785-H790
Author(s):  
T. Sakamoto ◽  
W. W. Monafo
Keyword(s):  
Spinal Cord ◽  
Blood Flow ◽  
Brain Stem ◽  
Regional Blood Flow ◽  
Experimental Conditions ◽  
Pentobarbital Sodium ◽  
Arterial Blood ◽  
Group A ◽  
Group B ◽  
The Brain

[14C]butanol tissue uptake was used to measure simultaneously regional blood flow in three regions of the brain (cerebral and cerebellar hemispheres and brain stem) and in five levels of the spinal cord in 10 normothermic rats (group A) and in 10 rats in which rectal temperature had been lowered to 27.7 +/- 0.3 degrees C by applying ice to the torso (group B). Pentobarbital sodium anesthesia was used. Mean arterial blood pressure varied minimally between groups as did arterial pH, PO2, and PCO2. In group A, regional spinal cord blood flow (rSCBF) varied from 49.7 +/- 1.6 to 62.6 +/- 2.1 ml.min-1.100 g-1; in brain, regional blood flow (rBBF) averaged 74.4 +/- 2.3 ml.min-1.100 g-1 in the whole brain and was highest in the brain stem. rSCBF in group B was elevated in all levels of the cord by 21-34% (P less than 0.05). rBBF, however, was lowered by 21% in the cerebral hemispheres (P less than 0.001) and by 14% in the brain as a whole (P less than 0.05). The changes in calculated vascular resistance tended to be inversely related to blood flow in all tissues. We conclude that rBBF is depressed in acutely hypothermic pentobarbital sodium-anesthetized rats, as has been noted before, but that rSCBF rises under these experimental conditions. The elevation of rSCBF in hypothermic rats confirms our previous observations.

scholarly journals Role of Nitric Oxide in Regulation of Brain Stem Circulation during Hypotension

1997 ◽  
Vol 17 (10) ◽  
pp. 1089-1096 ◽  
Author(s):  
Kazunori Toyoda ◽  
Kenichiro Fujii ◽  
Setsuro Ibayashi ◽  
Tetsuhiko Nagao ◽  
Takanari Kitazono ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Brain Stem ◽  
Topical Application ◽  
Basilar Artery ◽  
Group Versus ◽  
Control Group ◽  
Cranial Window ◽  
Severe Hypotension ◽  
The Brain

We tested the hypothesis that nitric oxide (NO) plays a role in CBF autoregulation in the brain stem during hypotension. In anesthetized rats, local CBF to the brain stem was determined with laser-Doppler flowmetry, and diameters of the basilar artery and its branches were measured through an open cranial window during stepwise hemorrhagic hypotension. During topical application of 10−5 mol/L and 10−4 mol/L Nω-nitro-L-arginine (L-NNA), a nonselective inhibitor of nitric oxide synthase (NOS), CBF started to decrease at higher steps of mean arterial blood pressure in proportion to the concentration of L-NNA in stepwise hypotension (45 to 60 mm Hg in the 10−5 mol/L and 60 to 75 mm Hg in the 10−4 mol/L L-NNA group versus 30 to 45 mm Hg in the control group). Dilator response of the basilar artery to severe hypotension was significantly attenuated by topical application of L-NNA (maximum dilatation at 30 mm Hg: 16 ± 8% in the 10−5 mol/L and 12 ± 5% in the 10−4 mol/L L-NNA group versus 34 ± 4% in the control group), but that of the branches was similar between the control and L-NNA groups. Topical application of 10−5 mol/L 7-nitro indazole, a selective inhibitor of neuronal NOS, did not affect changes in CBF or vessel diameter through the entire pressure range. Thus, endothelial but not neuronal NO seems to take part in the regulation of CBF to the the brain stem during hypotension around the lower limits of CBF autoregulation. The role of NO in mediating dilatation in response to hypotension appears to be greater in large arteries than in small ones.

scholarly journals New optical method for analyzing cortical blood flow heterogeneity in small animals: validation of the method

2000 ◽  
Vol 279 (3) ◽  
pp. H1291-H1298 ◽  
Author(s):  
Istvan Schiszler ◽  
Minoru Tomita ◽  
Yasuo Fukuuchi ◽  
Norio Tanahashi ◽  
Koji Inoue
Keyword(s):  
Blood Flow ◽  
Mean Transit Time ◽  
Region Of Interest ◽  
Brain Parenchyma ◽  
Sprague Dawley ◽  
Doppler Flowmetry ◽  
Cranial Window ◽  
Brain Surface ◽  
Fine Glass ◽  
The Brain

In pentobarbital-anesthetized male Sprague-Dawley rats, a small cranial window was trephined, and the cortex was transilluminated with a fine glass fiber inserted into the brain parenchyma. The light intensity at the surface area of 2 × 2 mm was recorded during intracarotid injection of 25 μl of carbon black (CB) solution. The region of interest (ROI) was divided into a 50 × 50 matrix, and the mean transit time of CB transport was calculated in each matrix element. We found rapid transits of CB along the microvasculature, with considerable heterogeneity in the avascular area, and heterogeneous efficiency in autoregulatory capacity in the ROI during hypotension. The method was validated by comparison with laser-Doppler flowmetry. The average mean difference was 0.03 ± 0.05%. Five percent CO2 inhalation increased the flow by 85%, but heterogeneously. We concluded that the technique is exclusively sensitive to indicator transits in a very small area on the brain surface with potential usefulness in detecting regional heterogeneity in blood flow.

scholarly journals Role of the basilar artery in regulation of blood flow to the brain stem in rats.

Stroke ◽  
1991 ◽  
Vol 22 (6) ◽  
pp. 763-767 ◽  
Author(s):  
K Fujii ◽  
D D Heistad ◽  
F M Faraci
Keyword(s):  
Blood Flow ◽  
Brain Stem ◽  
Basilar Artery ◽  
The Brain

The influence of nitric oxide synthase 1 on blood flow and interstitial nitric oxide in the kidney

2001 ◽  
Vol 281 (1) ◽  
pp. R91-R97 ◽  
Author(s):  
Masao Kakoki ◽  
Ai-Ping Zou ◽  
David L. Mattson
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Renal Cortex ◽  
In Vivo Microdialysis ◽  
Sprague Dawley ◽  
Selective Inhibitors ◽  
Renal Vasculature ◽  
Doppler Flowmetry ◽  
Arterial Blood

The role of nitric oxide (NO) produced by NO synthase 1 (NOS1) in the renal vasculature remains undetermined. In the present study, we investigated the influence of systemic inhibition of NOS1 by intravenous administration of N ω-propyl-l-arginine (l-NPA; 1 mg · kg−1 · h−1) and N 5-(1-imino-3-butenyl)-l-ornithine (v-NIO; 1 mg · kg−1 · h−1), highly selective NOS1 inhibitors, on renal cortical and medullary blood flow and interstitial NO concentration in Sprague-Dawley rats. Arterial blood pressure was significantly decreased by administration of both NOS1-selective inhibitors (−11 ± 1 mmHg with l-NPA and −7 ± 1 mmHg with v-NIO; n = 9/group). Laser-Doppler flowmetry experiments demonstrated that blood flow in the renal cortex and medulla was not significantly altered following administration of either NOS1-selective inhibitor. In contrast, the renal interstitial level of NO assessed by an in vivo microdialysis oxyhemoglobin-trapping technique was significantly decreased in both the renal cortex (by 36–42%) and medulla (by 32–40%) following administration of l-NPA ( n = 8) or v-NIO ( n = 8). Subsequent infusion of the nonspecific NOS inhibitor N ω-nitro-l-arginine methyl ester (l-NAME; 50 mg · kg−1 · h−1) to rats pretreated with either of the NOS1-selective inhibitors significantly increased mean arterial pressure by 38–45 mmHg and significantly decreased cortical (25–29%) and medullary (37–43%) blood flow. In addition, l-NAME further decreased NO in the renal cortex (73–77%) and medulla (62–71%). To determine if a 40% decrease in NO could alter renal blood flow, a lower dose ofl-NAME (5 mg · kg−1 · h−1; n = 8) was administered to a separate group of rats. The low dose of l-NAME reduced interstitial NO (cortex 39%, medulla 38%) and significantly decreased blood flow (cortex 23–24%, medulla 31–33%). These results suggest that NOS1 does not regulate basal blood flow in the renal cortex or medulla, despite the observation that a considerable portion of NO in the renal interstitial space appears to be produced by NOS1.

Cortical cerebral blood flow cycling: anesthesia and arterial blood pressure

1995 ◽  
Vol 268 (2) ◽  
pp. H569-H575 ◽  
Author(s):  
S. C. Jones ◽  
J. L. Williams ◽  
M. Shea ◽  
K. A. Easley ◽  
D. Wei
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Pressure Change ◽  
Sprague Dawley ◽  
Doppler Flowmetry ◽  
Blood Withdrawal ◽  
Cranial Window ◽  
Arterial Blood ◽  
Mean Pressure

Cycling of various cerebral metabolic substances, arterial vascular diameter, and flow has been noted by many workers at a frequency near 0.1 Hz. Suspicion that this phenomenon is dependent on the type of anesthesia led us to investigate the occurrence of cerebral blood flow (CBF) cycling with different anesthetics. Fifteen Sprague-Dawley rats were anesthetized with either pentobarbital (n = 5, 40–50 mg/kg), alpha-chloralose (n = 5, 60 mg/kg), or halothane (n = 5, 1–0.5%). Body temperature was maintained at 37 degrees C. Femoral arterial and venous catheters were placed, and a tracheotomy was performed, permitting artificial ventilation with 30% O2–70% N2. A closed cranial window was formed over a 3-mm diameter craniotomy. Mean arterial pressure (MABP), arterial partial pressures of CO2 and O2 (PaCO2 and PaO2), and pH were controlled and stabilized at normal values. CBF was determined using laser Doppler flowmetry. To induce cycling, MABP was transiently and repeatedly lowered by exsanguination. Fast Fourier analysis of selected 64-s flow recordings (n = 38) was performed. CBF cycling was observed, independent of the type of anesthesia, in all animals. In 36 epochs, cycling was induced when MABP was reduced to a mean pressure of 65 +/- 1.5 mmHg. The mean frequency and amplitude were 0.094 +/- 0.003 Hz and 6.6 +/- 0.5%, respectively. Cycling occurred without blood withdrawal in two epochs. With the use of the blood-withdrawal epochs (n = 36), all three anesthetics shared a common linear slope between amplitude and blood pressure (P < 0.02) and blood pressure change (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Effect of Renin on Brain Arterioles and Cerebral Blood Flow in Rabbits

1996 ◽  
Vol 16 (4) ◽  
pp. 714-719 ◽  
Author(s):  
Roman L. Haberl ◽  
Pamla J. Decker-Hermann ◽  
Klaus Hermann
Keyword(s):  
Blood Flow ◽  
Renin Angiotensin System ◽  
Rabbit Brain ◽  
Angiotensin I ◽  
Doppler Flowmetry ◽  
Cranial Window ◽  
Brain Surface ◽  
Pial Vessel ◽  
The Brain ◽  
Stimulation Of

There is evidence of an intrinsic renin–angiotensin system in the brain. The goal of the study was to determine whether stimulation of endogenous angiotensin production by applying renin to the brain surface has an effect on pial arteriolar caliber and CBF. Pial vessel diameters were measured through a closed cranial window in anesthetized rabbits. Percent changes of blood flow in the cortical area under the cranial window were simultaneously measured by laser-Doppler flowmetry. Topical application of 0.01–0.1 U/ml renin induced maximum dilation of 18.9 ± 4% (mean ± SD) of pial arterioles within 2 min. Arteriolar calibers thereafter decreased slowly. Flow gradually increased to peak at 38 ± 15% 50 min after renin application. Angiotensin I levels in jugular blood, as measured by radioimmunoassay, increased to a peak 40 min after topical renin application. Angiotensin II levels in jugular blood and both angiotensin I and II levels in blood samples from the femoral artery did not change. Diameter and flow changes were inhibited by intravenous pretreatment with the converting enzyme blocker captopril (10 mg/kg body wt i.v.). Captopril did not affect the vasodilation and flow increase in response to hypercapnia. Topically applied Captopril (10−5 M) blocked renin-induced arteriolar dilation. We conclude that renin increases pial arteriolar diameters and cortical blood flow in the rabbit brain. Stimulation of angiotensin production is likely to be a mediator of this response.

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