Effect of norepinephrine on rat basilar artery in vivo

1993 ◽  
Vol 264 (1) ◽  
pp. H178-H182 ◽  
Author(s):  
T. Kitazono ◽  
F. M. Faraci ◽  
D. D. Heistad
Keyword(s):  
Basilar Artery ◽  
Selective Inhibitor ◽  
K Channels ◽  
Cranial Window ◽  
Relaxing Factor ◽  
Endothelium Derived Relaxing Factor ◽  
Oxide Synthase ◽  
Dependent Mechanism ◽  
Direct Activator

In anesthetized rats, we used a cranial window to examine effects of topical norepinephrine on diameter of the basilar artery in vivo. Topical application of norepinephrine increased the diameter of the basilar artery. NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, inhibited vasodilatation to acetylcholine but did not attenuate dilator responses to norepinephrine. Indomethacin also did not attenuate vasodilatation in response to norepinephrine. Dilatation of the basilar artery to norepinephrine was inhibited by propranolol and the beta 1-antagonist atenolol but not by the beta 2-antagonist butoxamine. Thus dilatation of the basilar artery in response to norepinephrine is produced by activation of beta 1-receptors and is not mediated by endothelium-derived relaxing factor or prostanoids. Glibenclamide, a selective inhibitor of ATP-sensitive K+ channels, partially inhibited vasodilatation in response to norepinephrine. Forskolin, a direct activator of adenylate cyclase, also increased the diameter of the basilar artery, and glibenclamide attenuated the dilatation. Thus dilatation of rat basilar artery in response to norepinephrine is mediated, in part, by activation of ATP-sensitive K+ channels, and activation of these K+ channels may be achieved by an adenosine 3',5'-cyclic monophosphate-dependent mechanism.

Role of ATP-sensitive K+ channels in CGRP-induced dilatation of basilar artery in vivo

1993 ◽  
Vol 265 (2) ◽  
pp. H581-H585 ◽  
Author(s):  
T. Kitazono ◽  
D. D. Heistad ◽  
F. M. Faraci
Keyword(s):  
Basilar Artery ◽  
Minor Component ◽  
K Channels ◽  
Cranial Window ◽  
Calcitonin Gene ◽  
A Minor ◽  
Oxide Synthase ◽  
Camp Levels

Stimulation of adenylate cyclase appears to activate ATP-sensitive K+ channels in the basilar artery. We tested the hypothesis that calcitonin gene-related peptide (CGRP), which increases intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels, activates ATP-sensitive K+ channels and thereby causes vasodilatation. Using a cranial window in anesthetized rats, we examined responses of the basilar artery to CGRP in vivo. We also examined responses of the artery to another vasoactive peptide, vasoactive intestinal peptide (VIP). Topical application of CGRP (10(-11) to 10(-8) M) increased diameter of the basilar artery. Responses of the basilar artery to CGRP were almost abolished by a CGRP1 receptor antagonist, CGRP-(8-37). Vasodilatation in response to VIP was much smaller than that produced by CGRP. Dilator responses of the basilar artery to 10(-9) and 10(-8) M CGRP were inhibited by glibenclamide (10(-6) M), a selective inhibitor of ATP-sensitive K+ channels, by 69 +/- 19 and 41 +/- 9%, respectively. NG-nitro-L-arginine methyl ester (10(-5) M), an inhibitor of nitric oxide synthase, did not attenuate dilator response to 10(-8) M CGRP but inhibited responses to 10(-9) M CGRP by 34 +/- 12%. Indomethacin did not alter dilator responses to CGRP. These findings suggest that a minor component of CGRP-induced dilatation of the basilar artery is mediated by endothelium-derived relaxing factor. Vasodilatation in response to CGRP appears to be mediated primarily by direct activation of CGRP1 receptors on vascular muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional activity of Ca2+-dependent K+ channels is increased in basilar artery during chronic hypertension

1997 ◽  
Vol 272 (3) ◽  
pp. H1287-H1291 ◽  
Author(s):  
R. Paterno ◽  
D. D. Heistad ◽  
F. M. Faraci
Keyword(s):  
Arterial Pressure ◽  
Basilar Artery ◽  
Vessel Diameter ◽  
Chronic Hypertension ◽  
Spontaneously Hypertensive ◽  
K Channels ◽  
Cranial Window ◽  
Wistar Kyoto ◽  
Oxide Synthase

We examined the hypothesis that activity of Ca2+-dependent K+ channels is increased in the basilar artery during chronic hypertension. Diameter of the basilar artery was measured using a cranial window in anesthetized normotensive Wistar-Kyoto rats (WKY, arterial pressure = 109 +/- 3 mmHg, mean +/- SE) and stroke-prone spontaneously hypertensive rats (SHRSP, arterial pressure = 179 +/- 4 mmHg). Responses of the basilar artery to topical application of tetraethylammonium ion (TEA), an inhibitor of Ca2+-dependent K+ channels, were examined in WKY and SHRSP. Vessel diameter decreased by 2 +/- 1 and 4 +/- 0.1% in WKY and by 7 +/- 2 and 18 +/- 1% in SHRSP (P < 0.05 vs. WKY) in response to 10(-4) and 10(-3) M TEA, respectively. Similar results were obtained using iberiotoxin (10(-8) and 10(-7) M), a highly selective inhibitor of Ca2+-dependent K+ channels. In contrast to constrictor responses to TEA and iberiotoxin, constrictor responses of the basilar artery in response to serotonin and U-46619 were similar in WKY and SHRSP. In WKY rats that were made chronically hypertensive (arterial pressure = 172 +/- 6 mmHg) after treatment for 4 wk with N(G)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, constriction of the basilar artery in response to TEA was also enhanced. These findings suggest that activity of Ca2+-dependent K+ channels is enhanced in the basilar artery in vivo in two models of chronic hypertension. Thus Ca2+-dependent K+ channels in the basilar artery may be activated during chronic hypertension, perhaps as a response to elevation of intracellular concentration of Ca2+.

Effect of nitric oxide and potassium channel agonists and inhibitors on basilar artery diameter

1997 ◽  
Vol 272 (1) ◽  
pp. H256-H262 ◽  
Author(s):  
C. G. Sobey ◽  
F. M. Faraci
Keyword(s):  
Nitric Oxide ◽  
Sodium Nitroprusside ◽  
Basilar Artery ◽  
Selective Inhibitor ◽  
No Production ◽  
No Donor ◽  
K Channels ◽  
Cranial Window ◽  
Endogenous Production ◽  
Direct Activator

The first goal of this study was to examine the hypothesis that dilatation of the basilar artery in response to activation of ATP-sensitive K+ channels is mediated by nitric oxide (NO). Diameter of the basilar artery (209 +/- 5 microns, mean +/- SE) was measured using a cranial window in anesthetized rats. Aprikalim (a direct activator of ATP-sensitive K+ channels) dilated the basilar artery under control conditions. Inhibition of endogenous NO production with NG-nitro-L-arginine (L-NNA, 10(-4) M) did not alter responses to aprikalim. The second goal was to determine whether vasodilatation in response to NO is dependent on activation of calcium-activated K+ channels. Tetraethylammonium (TEA, 10(-3) M), an inhibitor of calcium-activated K+ channels, did not affect dilator responses to sodium nitroprusside (an NO donor) under control conditions. Responses to nitroprusside (10(-8) and 10(-7) M) were augmented more than twofold during application of L-NNA. In the presence of L-NNA, the augmented portion of the response to nitroprusside was inhibited by TEA and iberiotoxin (5 x 10(-8) M, a highly selective inhibitor of calcium-activated K+ channels), but it was not inhibited by glibenclamide (10(-6) M), an inhibitor of ATP-sensitive K+ channels. These findings suggest that dilator responses of the basilar artery to an activator of ATP-sensitive potassium channels are not mediated by NO. Calcium-activated K+ channels may not normally contribute to dilator responses of the basilar artery to nitroprusside. The effects of TEA and iberiotoxin suggest that when endogenous production of NO is inhibited, sodium nitroprusside causes the opening of calcium-activated K+ channels, contributing to an augmented vasodilator response.

Role of ATP-sensitive potassium channels in the basilar artery

1993 ◽  
Vol 264 (1) ◽  
pp. H8-H13 ◽  
Author(s):  
F. M. Faraci ◽  
D. D. Heistad
Keyword(s):  
Potassium Channels ◽  
Basilar Artery ◽  
Cranial Window ◽  
Basal Tone ◽  
Dependent Inhibition ◽  
Baseline Diameter ◽  
Direct Activator ◽  
Sustained Increase

This study examined the hypothesis that activation of ATP-sensitive potassium channels produces vasodilation and contributes to dilator responses of the basilar artery to acetylcholine in vivo. Diameter of the basilar artery (baseline diam = 245 +/- 14 microns, means +/- SE) was measured through a cranial window in anesthetized rats. RP52891 (1 microM), a direct activator of ATP-sensitive potassium channels, increased the diameter of the basilar artery by 33 +/- 5%. Glibenclamide (1 microM), an inhibitor of ATP-sensitive potassium channels, did not alter baseline diameter but abolished responses of the basilar artery to RP52891. Topical application of acetylcholine (10 microM) for 3 min produced peak dilatation of 33 +/- 6% at 30 s and produced a sustained increase in diameter of 17 +/- 4%. Glibenclamide did not inhibit dilator responses of the basilar artery to acetylcholine. Nitro-L-arginine methyl ester (10 and 100 microM), which inhibits synthesis of endothelium-derived relaxing factor (EDRF), produced concentration-dependent inhibition of dilatation of the basilar artery in response to acetylcholine. Thus ATP-sensitive potassium channels are functional but do not appear to influence basal tone of the basilar artery. Dilator responses of the basilar artery to acetylcholine are dependent on formation of EDRF but not dependent on activity of glibenclamide-sensitive potassium channels.

Subarachnoid hemorrhage inhibition of endothelium-derived relaxing factor in rabbit basilar artery

1988 ◽  
Vol 69 (2) ◽  
pp. 247-253 ◽  
Author(s):  
Kazuhiro Hongo ◽  
Neal F. Kassell ◽  
Tadayoshi Nakagomi ◽  
Tomio Sasaki ◽  
Tetsuya Tsukahara ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Basilar Artery ◽  
Selective Inhibitor ◽  
Isometric Tension ◽  
The Other ◽  
Content Type ◽  
Relaxing Factor ◽  
Endothelium Derived Relaxing Factor ◽  
Fine Print

✓ Vascular contractions in response to KCl and serotonin (5-hydroxytryptamine, 5-HT) in rabbit basilar artery were studied in vitro using an isometric tension-measurement technique. Hemoglobin ( 10−5 M) markedly augmented contractions induced by 5-HT (10−9 to 10−6 M) and slightly augmented those induced by KCl (20 to 80 mM) in arteries with intact endothelium. On the other hand, the augmentation induced by hemoglobin was almost abolished in arteries that were chemically denuded of endothelial cells by pretreatment with saponin. Since hemoglobin is known to be a selective inhibitor of endothelium-derived relaxing factor (EDRF), it is possible that the augmentation of contraction by hemoglobin in endothelium-intact arteries was mediated via an inhibition of spontaneously released EDRF. The effect of subarachnoid hemorrhage (SAH) on spontaneously released EDRF was investigated by injecting 5 ml of blood into the cisterna magna and sacrificing the rabbits 2 days later. Arteries after SAH showed a significant reduction in hemoglobin-induced augmentation compared to that seen in control arteries with intact endothelium. This result suggests that spontaneously released EDRF is significantly reduced after SAH. It is concluded that EDRF is released spontaneously in the rabbit basilar artery and that inhibition of its release might be involved in pathogenesis of cerebral vasospasm.

Acute compensation to abrupt occlusion of rat femoral artery is prevented by NO synthase inhibitors

1994 ◽  
Vol 267 (6) ◽  
pp. H2523-H2530 ◽  
Author(s):  
J. L. Unthank ◽  
J. C. Nixon ◽  
M. C. Dalsing
Keyword(s):  
Femoral Artery ◽  
Arterial Occlusion ◽  
Artery Occlusion ◽  
No Synthase ◽  
Artery Blood Flow ◽  
Relaxing Factor ◽  
Femoral Artery Occlusion ◽  
Before And After ◽  
Endothelium Derived Relaxing Factor ◽  
Oxide Synthase

The hemodynamic significance of endothelium-derived relaxing factor (EDRF)-mediated mechanisms in vascular responses to abrupt rat femoral artery occlusion was investigated. Temporary arterial occlusion was produced before and after inhibition of nitric oxide synthase by N omega-nitro-L-arginine methyl ester (L-NAME) or NG-monomethyl-L-arginine (L-NMMA). Iliac artery blood flow and arterial pressures proximal and distal to the occlusion were measured. Normal vascular compensation included a return of resistance to preocclusion levels and a rise in distal pressure to a plateau within 5 min postocclusion. After treatment with L-NAME and L-NMMA, postocclusion resistance remained elevated by 53 and 36%, respectively. Collateral dilation after occlusion, as indicated by the rise in distal pressure, was prevented by L-NAME but not L-NMMA. Increases in adrenergic tone and mean arterial pressure by phenylephrine did not prevent compensation, suggesting the effects of L-NAME and L-NMMA did not result from elevated sympathetic activation or pressure. The results are consistent with the hypothesis that the stimulated release of endothelium-derived relaxing factor mediates the acute vascular compensation to abrupt arterial occlusion.

Regulation of native collateral vessel dilation after coronary occlusion in the dog

1994 ◽  
Vol 266 (2) ◽  
pp. H769-H778 ◽  
Author(s):  
K. G. Lamping ◽  
E. N. Bloom ◽  
D. G. Harrison
Keyword(s):  
Potassium Channels ◽  
Coronary Occlusion ◽  
Fluorescence Angiography ◽  
Collateral Vessel ◽  
K Channels ◽  
Relaxing Factor ◽  
Anesthetized Dogs ◽  
Endothelium Derived Relaxing Factor ◽  
Baseline Diameter

The purpose of this study was to examine mechanisms involved in the response of native collaterals to coronary occlusion. In anesthetized dogs native collaterals were identified as vessels coursing between the left anterior descending and left circumflex arteries using fluorescence angiography. After a left anterior descending occlusion in 12 dogs, collaterals < 100 microns in diameter progressively dilated by 21 +/- 4% (n = 12) 1 min after occlusion and by 39 +/- 6% 15 min after occlusion. Collaterals > 100 microns in diameter did not dilate after coronary occlusion. NG-nitro-L-arginine (1 mg/min intracoronary) caused constriction under basal conditions in collaterals < 100 microns but did not prevent the dilation of collaterals after occlusion. In contrast, glibenclamide (10(-5) M), an inhibitor of ATP-sensitive potassium channels, had no effect on baseline diameter of collaterals < 100 microns diameter but completely prevented dilation of collaterals after occlusion. We conclude that collaterals are not maximally dilated immediately after a coronary occlusion but rather progressively dilate for at least 15 min after an occlusion. This dilation of native collaterals after an occlusion is not mediated by release of an endothelium-derived relaxing factor derived from L-arginine but is mediated by activation of ATP-sensitive K+ channels.

Role of inwardly rectifying K+ channels in K+-induced cerebral vasodilatation in vivo

2000 ◽  
Vol 279 (6) ◽  
pp. H2704-H2712 ◽  
Author(s):  
Sophocles Chrissobolis ◽  
James Ziogas ◽  
Yi Chu ◽  
Frank M. Faraci ◽  
Christopher G. Sobey
Keyword(s):  
Basilar Artery ◽  
Channel Activity ◽  
Atpase Inhibitor ◽  
Kir Channel ◽  
Cerebral Vasodilatation ◽  
Nos Inhibitor ◽  
Oxide Synthase ◽  
Inwardly Rectifying

We tested whether activation of inwardly rectifying K+ (Kir) channels, Na+-K+-ATPase, or nitric oxide synthase (NOS) play a role in K+-induced dilatation of the rat basilar artery in vivo. When cerebrospinal fluid [K+] was elevated from 3 to 5, 10, 15, 20, and 30 mM, a reproducible concentration-dependent vasodilator response was elicited (change in diameter = 9 ± 1, 27 ± 4, 35 ± 4, 43 ± 12, and 47 ± 16%, respectively). Responses to K+ were inhibited by ∼50% by the Kir channel inhibitor BaCl2 (30 and 100 μM). In contrast, neither ouabain (1–100 μM, a Na+-K+-ATPase inhibitor) nor N G-nitro-l-arginine (30 μM, a NOS inhibitor) had any effect on K+-induced vasodilatation. These concentrations of K+ also hyperpolarized smooth muscle in isolated segments of basilar artery, and these hyperpolarizations were virtually abolished by 30 μM BaCl2. RT-PCR experiments confirmed the presence of mRNA for Kir2.1 in the basilar artery. Thus K+-induced dilatation of the basilar artery in vivo appears to partly involve hyperpolarization mediated by Kir channel activity and possibly another mechanism that does not involve hyperpolarization, activation of Na+-K+-ATPase, or NOS.

Effects of NG-substituted arginines on coronary vascular function after endotoxin

1993 ◽  
Vol 75 (1) ◽  
pp. 424-431 ◽  
Author(s):  
M. J. Winn ◽  
B. Vallet ◽  
N. K. Asante ◽  
S. E. Curtis ◽  
S. M. Cain
Keyword(s):  
Nitric Oxide ◽  
Vascular Function ◽  
Endotoxic Shock ◽  
No Synthase ◽  
Relaxing Factor ◽  
Nos Inhibitors ◽  
Nos Inhibitor ◽  
Endothelium Derived Relaxing Factor ◽  
Constrictor Response

We investigated the responses of canine coronary rings to endothelium-derived relaxing factor-nitric oxide- (EDRF-NO) dependent agonists and NO synthase (NOS) inhibitors 3 h after endotoxic shock was induced in dogs by lipopolysaccharide infusion (LPS; 2 mg/kg). EDRF-NO-dependent relaxation to thrombin [control maximum response produced after administration of thrombin (Emax) was -85.2 +/- 7.0% of the constrictor response produced by the thromboxane analogue U-46619], acetylcholine (control Emax -88.4 +/- 3.4%), or bradykinin (control Emax -80.5 +/- 2.2%) was not inhibited by LPS (Emax thrombin -75.9 +/- 9.5%; Emax acetylcholine -90.2 +/- 2.4%; Emax bradykinin -91.6 +/- 3.4%). The NOS inhibitor NG-monomethyl-L-arginine (L-NMMA) (10(-6)-3 x 10(-4) M) caused constriction of rings with endothelium (Emax 36.3 +/- 5.6%), an effect that was greater after LPS (Emax 59.2 +/- 4.1%; P < 0.05). D-NMMA had no effect in control, but it increased tension after LPS (Emax 20.8 +/- 9.7%). Contrary to expectations, L- and D-NMMA relaxed endothelium-denuded rings (-30.4 +/- 8.7% L-NMMA; -45.1 +/- 11.7% D-NMMA; P < 0.05). However, neither agent caused relaxation after in vivo LPS (10.2 +/- 3.4% L-NMMA; 8.9 +/- 5.2% D-NMMA). N omega-nitro-L-arginine-methylester (L-NAME) and nitro-L-arginine (10(-6)-3 x 10(-4) M) increased tension (Emax 82.3 +/- 23.9 and 73.1 +/- 8.8%, respectively) but only when endothelium was present, and the increases were no greater in LPS-treated groups than in controls (with LPS: Emax L-NAME 87.3 +/- 16.5%; Emax nitro-L-arginine 65.7 +/- 3.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

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