Mechanics of large and small cerebral arteries in chronic hypertension

1994 ◽  
Vol 266 (3) ◽  
pp. H1027-H1033 ◽  
Author(s):  
M. A. Hajdu ◽  
G. L. Baumbach
Keyword(s):  
Cerebral Artery ◽  
Posterior Cerebral Artery ◽  
Cerebral Arteries ◽  
Internal Diameter ◽  
Chronic Hypertension ◽  
External Diameter ◽  
Cross Sectional ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto

The goal of this study was to investigate factors that contribute to reductions in internal diameter of large and small cerebral arteries during chronic hypertension. We measured diameter of second- and third-order branches of the posterior cerebral artery in vitro during maximal dilation with EDTA in 6-mo-old stroke-prone spontaneously hypertensive rats (SHRSP, n = 7) and Wistar-Kyoto rats (WKY, n = 7). Cross-sectional area of the vessel wall, measured histologically, was not significantly different at 70 mmHg in SHRSP and WKY in large or small branches of posterior cerebral artery. In large branches of posterior cerebral artery, external and internal diameters were significantly less at 70 mmHg in SHRSP than in WKY, whereas external and internal diameters converged at 0 mmHg in the two groups of rats. In small branches, on the other hand, external and internal diameters were significantly less at all levels of intravascular pressure in SHRSP than in WKY. The stress-strain relation in posterior cerebral artery of SHRSP was shifted to the left in large branches and to the right in small branches, which indicates that distensibility was reduced in large cerebral arteries of SHRSP and increased in small cerebral arteries. These findings suggest that different mechanisms are responsible for impairment of maximal dilator capacity in large and small cerebral arteries of SHRSP: reduced distensibility in large arteries and remodeling with reduced external diameter in small arteries. Furthermore the findings provide additional support for the concept that hypertrophy may not be a primary factor in impaired maximal dilation.

Myogenic and structural properties of cerebral arteries from the stroke-prone spontaneously hypertensive rat

2003 ◽  
Vol 285 (4) ◽  
pp. H1489-H1494 ◽  
Author(s):  
Ashley S. Izzard ◽  
Delyth Graham ◽  
Matthew P. Burnham ◽  
Egidius H. Heerkens ◽  
Anna F. Dominiczak ◽  
...  
Keyword(s):  
Structural Properties ◽  
Spontaneously Hypertensive Rat ◽  
Cerebral Arteries ◽  
Systolic Pressure ◽  
Cross Sectional ◽  
Spontaneously Hypertensive ◽  
Hypertensive Rat ◽  
Constant Diameter ◽  
Strain Relationship

The aims of the study were to compare the myogenic and structural properties of middle cerebral arteries (MCAs) from the stroke-prone spontaneously hypertensive rat (SHRSP) with MCAs from the spontaneously hypertensive rat (SHR) before stroke development in SHRSP. Rats were fed a “Japanese” diet (low-protein rat chow and 1% NaCl in drinking water) for 8 wk, and cerebral arteries were studied in vitro at 12 wk using a pressure arteriograph. Systolic pressure was significantly increased in SHRSP compared with SHR at 12 wk. Between 60 and 180 mmHg, MCAs from SHR maintained an essentially constant diameter, i.e., displayed a “myogenic range,” whereas the diameter of MCAs from SHRSP progressively increased as a function of pressure. Passive lumen diameter of MCAs from SHRSP was reduced at high pressure, and wall thickness and wall/lumen were increased, compared with SHR. Wall cross-sectional area was also increased in MCAs from SHRSP compared with the SHR, indicating growth. The stress-strain relationship was shifted to the left in MCAs from SHRSP, indicating decreased MCA distensibility compared with SHR. However, collagen staining with picrosirius red revealed a redistribution of collagen to the outer half of the MCA wall in SHRSP compared with SHR. These data demonstrate impaired myogenic properties in prestroke SHRSP compared with SHR, which may explain stroke development. The structural differences in MCAs from SHRSP compared with SHR were a consequence of both growth and a reduced distensibility.

scholarly journals “True Fetal Posterior Cerebral Artery”: Rare Variant Mimics AVM on MRI

Neurographics ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 71-74
Author(s):  
E.L. Perez ◽  
A. Wang ◽  
P. Meyers
Keyword(s):  
Cerebral Artery ◽  
Posterior Cerebral Artery ◽  
Cerebral Arteries ◽  
Cerebral Vasculature ◽  
Brain Arteriovenous Malformation ◽  
Cross Sectional ◽  
Cross Sectional Imaging ◽  
Anterior Choroidal ◽  
Rare Anatomic Variant ◽  
Choroidal Artery

A “true fetal posterior cerebral artery” is an extremely rare anatomic variant of the cerebral vasculature in which 2 independent posterior cerebral arteries are present; 1 arises from a persistent large primitive anterior choroidal artery and a second arises in the usual fashion. This case report demonstrates this diagnosis made using cerebral angiography in a young woman with nonspecific headaches whose MR imaging brain scan was originally interpreted as a brain arteriovenous malformation or dural arteriovenous fistula. Given the rarity of a true fetal posterior cerebral artery, awareness of this entity may make it discernible on cross-sectional imaging. In addition, it is important to be able to recognize this angiographically because this variant supplies posterior cerebral structures and should not be embolized.

Spontaneous vasomotion in pressurized cerebral arteries from genetically hypertensive rats

1988 ◽  
Vol 254 (1) ◽  
pp. H28-H33 ◽  
Author(s):  
G. Osol ◽  
W. Halpern
Keyword(s):  
Contractile Activity ◽  
Cerebral Arteries ◽  
Potassium Conductance ◽  
Physiological Saline ◽  
Spontaneously Hypertensive ◽  
Genetically Hypertensive Rats ◽  
Physiological Saline Solution ◽  
Wistar Kyoto ◽  
Rhythmic Contractile Activity

Resistance-sized branches of posterior cerebral arteries from Wistar-Kyoto (WKY), spontaneously hypertensive (SHR), spontaneously hypertensive stroke-prone (SHRSP), and antihypertensive-treated SHRSP (SHRSP-TRT) rats were studied in vitro. After the rats were killed, arterial segments were excised, mounted on microcannulas, and pressurized. After equilibration, intravascular pressure was increased in a stepwise fashion from 30 to 150-200 mmHg. All vessels developed a myogenic tone, which resulted in diameter reductions of 31-37% at 100 mmHg when compared with fully relaxed diameters [approximately 200 micron in 1 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid]. Differences in the extent of tone were not significant between animal groups (P greater than 0.05). Rhythmic vasomotion was present in 94% SHRSP and 100% SHRSP-TRT, 83% SHR, and only 6% of the WKY arteries. At higher pressures, the amplitude of the diameter oscillations decreased and frequency increased. Vasomotion was unaltered by tetrodotoxin or indomethacin, but could be abolished by cooling to 34 degrees C, ouabain (a depolarizing solution containing 125 mM K+), potassium-free physiological saline solution, or by calcium entry blockade with diltiazem or MnCl2. In normally quiescent WKY arteries, vasomotion, which was qualitatively similar to that observed in the hypertensive strains, could be induced by the addition of 5 mM tetraethylammonium chloride. Thus intrinsic oscillations in membrane calcium and potassium conductance may underlie the rhythmic contractile activity of rat cerebral arteries. This property appears to have a major genetic component, the expression of which is relatively independent of blood pressure history and is not related to the myogenic properties of the preparation.

scholarly journals Loss of cerebrovascular Shaker-type K+ channels: a shared vasodilator defect of genetic and renal hypertensive rats

2009 ◽  
Vol 297 (1) ◽  
pp. H293-H303 ◽  
Author(s):  
Ann A. Tobin ◽  
Biny K. Joseph ◽  
Hamood N. Al-Kindi ◽  
Sulayma Albarwani ◽  
Jane A. Madden ◽  
...  
Keyword(s):  
Cerebral Arteries ◽  
Chronic Hypertension ◽  
Mrna Levels ◽  
Hypertensive Rats ◽  
Western Blots ◽  
Spontaneously Hypertensive ◽  
Rat Models ◽  
Middle Cerebral Arteries ◽  
Wistar Kyoto ◽  
Renal Hypertensive Rats

The cerebral arteries of hypertensive rats are depolarized and highly myogenic, suggesting a loss of K+ channels in the vascular smooth muscle cells (VSMCs). The present study evaluated whether the dilator function of the prominent Shaker-type voltage-gated K+ (KV1) channels is attenuated in middle cerebral arteries from two rat models of hypertension. Block of KV1 channels by correolide (1 μmol/l) or psora-4 (100 nmol/l) reduced the resting diameter of pressurized (80 mmHg) cerebral arteries from normotensive rats by an average of 28 ± 3% or 26 ± 3%, respectively. In contrast, arteries from spontaneously hypertensive rats (SHR) and aortic-banded (Ao-B) rats with chronic hypertension showed enhanced Ca2+-dependent tone and failed to significantly constrict to correolide or psora-4, implying a loss of KV1 channel-mediated vasodilation. Patch-clamp studies in the VSMCs of SHR confirmed that the peak K+ current density attributed to KV1 channels averaged only 5.47 ± 1.03 pA/pF, compared with 9.58 ± 0.82 pA/pF in VSMCs of control Wistar-Kyoto rats. Subsequently, Western blots revealed a 49 ± 7% to 66 ± 7% loss of the pore-forming α1.2- and α1.5-subunits that compose KV1 channels in cerebral arteries of SHR and Ao-B rats compared with control animals. In each case, the deficiency of KV1 channels was associated with reduced mRNA levels encoding either or both α-subunits. Collectively, these findings demonstrate that a deficit of α1.2- and α1.5-subunits results in a reduced contribution of KV1 channels to the resting diameters of cerebral arteries from two rat models of hypertension that originate from different etiologies.

Rapid baroreceptor resetting is unaltered by chronic hypertension in rats

1989 ◽  
Vol 256 (4) ◽  
pp. H1228-H1235 ◽  
Author(s):  
M. C. Andresen ◽  
M. Y. Yang
Keyword(s):  
Aortic Distensibility ◽  
Chronic Hypertension ◽  
Spontaneously Hypertensive ◽  
Pressure Threshold ◽  
Blood Pressures ◽  
Wistar Kyoto ◽  
Strain Threshold ◽  
Simultaneous Discharge

This study compares rapid baroreceptor resetting in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Single-fiber baroreceptor activity and aortic diameter were measured in in vitro preparations. Baroreceptor pressure threshold (Pth) and suprathreshold pressure sensitivity were measured during periods after various levels of conditioning mean arterial pressure (cMAP). The ability of a baroreceptor to reset was expressed as the resetting ratio (delta Pth/delta cMAP). Rapid resetting was successfully characterized in 30 baroreceptors (18 SHR and 12 WKY). SHR blood pressures were higher, and aortic distensibility was lower than in WKY. SHR baroreceptors showed signs of chronic resetting, i.e., elevated Pth (105.4 vs. 88.5 mmHg, SHR and WKY, respectively) and decreased suprathreshold sensitivity (0.92 vs. 1.42 spikes.s.-1.mmHg-1, SHR and WKY, respectively), but their resetting ratios were similar to WKY (0.260 and 0.237, SHR and WKY, respectively). Characterization of rapid resetting of more than one baroreceptor from single animals reveals that the resetting ratio can vary by greater than 50% within animals. During simultaneous discharge-diameter recordings, the strain threshold was better correlated to cMAP than Pth. We conclude that the ability of baroreceptors to rapidly reset is unaltered by chronic hypertension or chronic baroreceptor resetting, and we hypothesize that rapid resetting is probably a result of an intrinsic neural property rather than vessel mechanics.

scholarly journals Territorial location of cerebral infarcts on imaging in patients with first ever stroke with diabetes

2014 ◽  
Vol 2 (1) ◽  
pp. 16-20
Author(s):  
Nirmalendu Bikash Bhowmik ◽  
Mohammad Saifuddin ◽  
Rajib Bhadra ◽  
Md Rashedul Islam ◽  
Rumana Habib ◽  
...  
Keyword(s):  
Middle Cerebral Artery ◽  
Cerebral Artery ◽  
Parietal Lobe ◽  
Posterior Cerebral Artery ◽  
Cerebral Arteries ◽  
Arterial System ◽  
Peripheral Vascular ◽  
Cross Sectional ◽  
The Mean ◽  
First Time

Aims: The study was aimed to evaluate vascular territories of infarcts involved in patients with stroke for the first time with diabetes on CT and/ or MRI of brain. Methodology: This cross sectional descriptive study was carried on a total of 100 adult patients with first ever stroke consecutively reported in the Department of Neurology, BIRDEM General Hospital, Dhaka, over a period of six months. Results: The mean age was 61.45 years and majority (35%) belongs to age group of 50-59. Ten (10%) subjects had age above 80 years. Male were 68% and 32% were female. Majority (89%) of the subjects had hemiplegia following acute stroke. Aphasia (71%), headache (39%), convulsion (23%), vomiting (18%) and cranial nerve palsy (17%) were also found. Additional preexisting risk factors were hypertension (72%), dyslipidaemia (59%), smoking (56%) and alcohol abuse (2%). Among the study subjects the diabetic complications were peripheral vascular disease (4% ), neuropathy (8%), nephropathy( 9%)and retinopathy(25%). CT scan and/ or MRI brain showed parietal lobe lesion in 57% cases. Majority (76%) had infarcts in middle cerebral artery territory. Involvement of anterior and posterior cerebral artery territory was found in 7% and 5% subjects respectively. Vertebro-basilar arterial system involvement was observed in 6% cases. 4% subjects had involvement of both middle and posterior cerebral arteries. Both anterior and posterior arterial territory infarcts were found in 2% cases. Conclusions: In conclusion most of the diabetic subjects with first ever ischemic stroke had involvement of middle cerebral artery. DOI: http://dx.doi.org/10.3329/bccj.v2i1.19951 Bangladesh Crit Care J March 2014; 2 (1): 16-20

Doppler evaluation of the posterior cerebral artery in fetuses with transposition of great arteries

2020 ◽  
Vol 48 (5) ◽  
pp. 504-508
Author(s):  
Ya Tan ◽  
Shi Zeng ◽  
YuShan Liu ◽  
HuaYu Tang ◽  
BaiHua Zhao
Keyword(s):  
Cerebral Artery ◽  
Pulsatility Index ◽  
Posterior Cerebral Artery ◽  
Cerebral Arteries ◽  
Peak Systolic Velocity ◽  
Transposition Of Great Arteries ◽  
Velocity Time Integral ◽  
Time Integral ◽  
Diastolic Velocity ◽  
Doppler Evaluation

AbstractObjectiveTo observe Doppler ultrasound changes in the two segments of the posterior cerebral artery (PCA) in fetuses with transposition of the great arteries (TGA).MethodsThe peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility index (PI), and velocity-time integral (VTI) of the two segments of PCA (the first segment: PCAS1, the second segment: PCAS2) and of the middle cerebral artery (MCA) were compared in TGA fetuses and normal fetuses. The abnormality rate between the PCAS1-PI and MCA-PI was compared in TGA fetuses.ResultsThe PCAS1-PI and MCA-PI were smaller in the TGA fetuses than in the controls (all P < 0.05), but the PCAS2-PI was unchanged (P > 0.05). The MCA-VTI, PCAS1-VTI, and PCAS2-VTI were larger in the TGA fetuses (all P < 0.05). In the TGA fetuses, the abnormality rate of the PCAS1-PI was significantly higher than that of the MCA-PI (P < 0.05).ConclusionIn fetuses with TGA, there were hemodynamic differences between the two segments of the posterior cerebral arteries. Moreover, PCAS1 exhibited signs of vasodilatation more obviously than did the MCA in fetuses with TGA.

Sex-specific differences in cerebral arterial myogenic tone in hypertensive and normotensive rats

2006 ◽  
Vol 290 (3) ◽  
pp. H1081-H1089 ◽  
Author(s):  
Jamila Ibrahim ◽  
Ann McGee ◽  
Delyth Graham ◽  
John C. McGrath ◽  
Anna F. Dominiczak
Keyword(s):  
Blood Flow ◽  
Cerebral Arteries ◽  
Systemic Blood Pressure ◽  
Limiting Factors ◽  
Myogenic Tone ◽  
Spontaneously Hypertensive ◽  
Cerebrovascular Events ◽  
Middle Cerebral Arteries ◽  
Wistar Kyoto ◽  
Strain Dependent

Cerebral blood flow (CBF) is maintained constant despite changes in systemic blood pressure (BP) through multiple mechanisms of autoregulation such as vascular myogenic reactivity. Our aim was to determine myogenic characteristics of cannulated middle cerebral arteries (MCA) in male and female stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) at 12 wk of age under pressurised no-flow conditions. MCA pressure-diameter relationships (20–200 mmHg) were constructed in active (with calcium) and passive (without calcium) conditions, and myogenic and mechanical properties were determined. Myogenic reactivity in WKY ( P < 0.05) and SHRSP ( P < 0.05) males was impaired compared with their female counterparts. Comparison of SHRSP with WKY in males revealed similar myogenic reactivity, but in females SHRSP exhibited augmented myogenic reactivity ( P < 0.05). In both sexes, myogenic tone yielded at lower pressure in SHRSP compared with WKY vessels (120–140 vs. 140–180 mmHg). Stress-strain relationships and elastic moduli in WKY rats showed that vessels were stiffer in females than in males. Conversely, in SHRSP, male vessels were stiffer than female vessels. Comparison of strains in males indicated that stiffness was increased in SHRSP compared with WKY vessels, whereas the converse was observed in females. These findings demonstrate that MCA myogenic and distensibility characteristics exhibit significant sex- and strain-dependent differences. Inappropriate myogenic adaptation and augmented vascular stiffness, particularly in male SHRSP, are potential limiting factors in blood flow autoregulation and may increase the predisposition for stroke-related cerebrovascular events.

Distensibility of the Left Atrial Wall in Spontaneously Hypertensive Rats Compared with That in Normotensive Wistar-Kyoto Rats

1980 ◽  
Vol 59 (s6) ◽  
pp. 361s-363s
Author(s):  
S.-E. Ricksten ◽  
T. Yao ◽  
B. Ljung ◽  
P. Thorean
Keyword(s):  
Left Atrial ◽  
Spontaneously Hypertensive Rats ◽  
Relative Length ◽  
Hypertensive Rats ◽  
Atrial Wall ◽  
Cross Sectional ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto Rats ◽  
Left Atrial Wall ◽  
Wistar Kyoto

1. The cardiac mechanoreceptors, which in rats are mainly located in the left atrial wall, are reset in spontaneously hypertensive rats. The atrial pressure has to be almost twice as high in spontaneously hypertensive rats as in normotensive controls to produce similar receptor activations, as is apparent from previous studies. 2. The present study was performed to investigate whether this resetting is due to decreased distensibility of left atrial walls in the spontaneously hypertensive rats. 3. Static load-length relationships were investigated in vitro on left atrial strips, and pressure-volume relationships were studied on isolated left atria from spontaneously hypertensive and normotensive Wistar-Kyoto rats. 4. The force per cross-sectional area exerted during a relative length increase of 80% was significantly greater in spontaneously hypertensive rats. The dynamic but not the static distensibility was significantly lower in these animals. 5. The decreased dynamic distensibility of left atrial walls in spontaneously hypertensive rats can at least partly explain the resetting of atrial receptor function.

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