UMLS:C0406810 - FACTA Search

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Query: UMLS:C0406810 (NAME)
13,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5-hydroxytryptamine (5-HT) has been reported to show some effects in respiratory tissues by activation of different subtype receptors. It has been demonstrated that 5-HT2 receptor activation causes in vivo and in vitro airways contraction and enhances effects of cholinergic nerve-mediated responses, whereas 5-HT1 receptor activation seems to be related to a relaxant effect. Moreover, in isolated guinea pig ascendens colon preparations 5-HT1 activation causes relaxation by involvement of nitric oxide (NO). The aim of this study was to investigate the effects of 5-HT1 receptor activation in guinea pig trachea as well as NO probable role in this activation. In tissues pretreated with both ketanserin (10 microM), an antagonist of 5-HT2 receptors, and ondansetron (10 microM), an antagonist of 5-HT3 receptors, 5-HT (from 10 nM to 10 mM) relaxed guinea pig trachea precontracted with acetylcholine (ACh, 100 microM). Carboxamidotryptamine (5-CT, from 10 nM to 10 mM), an agonist of 5-HT1 receptors, as well relaxed guinea pig trachea precontracted with ACh (100 microM). A pretreatment with NAN-190 (from 10 nM to 100 microM), a 5-HT1A selective antagonist, reduced the 5-HT and 5-CT relaxant effects but only at very high concentrations. Finally, a pretreatment with L-nitro-arginine-methyl-ester (L-NAME, 1 mM), an inhibitor of NO-synthase, and L-arginine (L-ARG, 1 mM), a precursor of NO synthesis, did not modify 5-HT and 5-CT responses in guinea pig trachea. In conclusion, this study suggests a 5-HT relaxant activity in guinea pig trachea via a 5-HT1 receptor activation without any NO pathway involvement. However, further investigations are needed to clarify which 5-HT1 receptor subtype is involved in 5-HT relaxant effect.
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PMID:Effects of in vitro 5-HT1 receptor activation in guinea pig trachea. 869 22

1. The function of endogenous nitric oxide (NO) at the level of vascular smooth muscle, was assessed in a popular experimental model of accelerated atherosclerosis, the cholesterol-fed rabbit. 2. Endothelium-dependent vasorelaxation in response to acetylcholine (ACh, 1 microM) was significantly impaired in the carotid artery from rabbits maintained on a 1% (W/W) cholesterol diet for 8-10 weeks. Furthermore, the ability of an inhibitor of nitric oxide synthase (NOS), NG-nitro-L-arginine methyl ester (L-NAME, 1-300 microM), to enhance the contractile reactivity to a submaximal concentration of noradrenaline (NA, 3 microM), was significantly attenuated in hypercholesterolaemia. 3. A significant linear correlation between the maximal contractile effect of L-NAME (300 microM) and maximal vasorelaxation to ACh (1 microM) was determined in the carotid artery from control rabbits. In contrast, no such linear correlation was found in the carotid artery from hypercholesterolaemic rabbits. 4. We conclude that there are lesions both in agonist-stimulated, endogenous NO-dependent vasorelaxation and in the regulation of vasoconstrictor reactivity by endogenous NO in the hypercholesterolaemic rabbit carotid artery. Furthermore, the normal linear relationship between the contractile effect of L-NAME and vasorelaxation to ACh is lost after cholesterol-feeding.
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PMID:Investigation of endogenous nitric oxide vascular function in the carotid artery of cholesterol-fed rabbits. 873 Jul 41

1. The canine isolated spleen was perfused at constant flow with warmed (37 degrees C) Krebs solution while the splenic arterial perfusion pressure (SAPP) and spleen weight were recorded continuously. An augmented smooth muscle tone was maintained by a continuous intra-arterial infusion of noradrenaline (0.01-0.1 mumol min-1) throughout the experiment. 2. Intra-arterial infusion of indomethacin (5.6 microM) significantly elevated (P < 0.05) the augmented vascular tone and the subsequent infusion of L-NAME (10 microM) further raised this vascular tone significantly (P < 0.01). 3. The splenic vasoconstrictor response to L-NAME was significantly (P < 0.05) reduced by the subsequent infusion of L-arginine (300 microM) but not of D-arginine (300 microM). 4. Neither L-NAME nor D-NAME had any effect on the basal vascular tone or the spleen weight in conditions of either basal or augmented tone. 5. Bolus injection of acetylcholine, substance P, sodium nitroprusside and isoprenaline caused short-lasting reductions in the SAPP. 6. The splenic vasodilator responses to ACh and SP, but not those to SNP and ISO, were significantly (P < 0.05) reduced by the infusion of L-NAME (10 microM), methylene blue (30 microM) but not of D-NAME (10 microM). 7. The reductions in the vasodilator responses to ACh and SP caused by L-NAME were partially reversed by L-arginine (300 microM), but not by D-arginine (300 microM). 8. The results demonstrate the contribution of nitric oxide (NO) release to the maintenance of the augmented splenic vascular tone and also the contribution of NO to the splenic vasodilator responses to ACh and SP.
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PMID:Involvement of nitric oxide in the smooth muscle tone of the isolated canine spleen and the responses to acetylcholine and substance P. 873 29

In addition to stretch, some hormones and neurotransmitters influence atrial natriuretic factor (ANF) secretion from the mammalian heart. In the present study, we investigated the effect of specific inhibition of nitric oxide/endothelium-derived relaxing factor (NO/ EDRF) on release of ANF from the isolated spontaneously beating heart during basal conditions and in response to arginine vasopressin (AVP; 3 x 10(-8) M), acetylcholine (ACh; 10(-6) M), and angiotensin II (ANG II; 4 x 10(-7) M) to determine whether NO is involved as a mediator of basal and hormone-modulated secretion of ANF. Basal secretion from control hearts remained stable for the duration of the experiment. Intracoronary perfusion of the heart with AVP, ACh, and ANG II reduced ANF secretion significantly by 58 +/- 4, 51 +/- 6, and 26 +/- 8%, respectively, independently of concomitant changes in coronary flow and heart rate. The NO donor sodium nitroprusside (SNP, 10(-4) M) inhibited ANF secretion comparably to AVP and ACh. The effect of SNP was not affected by inhibition of NO synthase activity with NG-nitro-L-arginine methyl ester (L-NAME; 3 x 10(-5) M). Similarly, L-arginine, (3 x 10(-4) M) but not its stereoisomer D-arginine (3 x 10(-4) M), significantly reduced ANF secretion. Subsequent perfusion with AVP singly or in combination with L-arginine or D-arginine did not affect ANF secretion further. The inhibitor of NO synthase NG-monomethyl-L-arginine (L-NMMA, 3 x 10(-5) M) did not affect basal secretion, but prevented the inhibitory effect of AVP and ACh. The effect of ANG II was not changed by L-NMMA. These results indicate that AVP and ACh inhibit ANF secretion in the isolated heart indirectly by stimulating NO/EDRF and suggest a novel function of NO/EDRF as a negative modulator of ANF secretion.
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PMID:Effect of nitric oxide inhibition on secretion of atrial natriuretic factor in isolated rat heart. 876 65

1. We have used anaesthetized, acutely instrumented non-pregnant (NP) and late pregnant (P) New Zealand white rabbits to examine the possible role of nitric oxide (NO) in the pregnancy-induced fall of vascular tone and arterial pressure. Systemic, renal and pulmonary vascular resistance, as well as plasma concentrations of cyclic GMP (PcGMP) were compared before and after the inhibition of NO synthesis by N(G)-nitro-L-arginine methyl ester (L-NAME). 2. P rabbits had lower baseline total peripheral resistance (TPR), mean arterial pressure (MAP) and higher PcGMP than NP controls (all P < 0.05 or less). L-NAME (1, 10, 50 mg kg1, i.v.) resulted in dose-dependent elevation of TPR in both groups. However, the absolute, as well as percentage increases in TPR were greater (P < 0.05) in NP than in P rabbits. 3. Cardiac output (CO) was reduced more (P < 0.01) by NO inhibition in NP than P rabbits. Therefore, despite the smaller increase in TPR, the elevation of MAP was greater (P < 0.001) in P than NP rabbits. After L-NAME, NP rabbits developed more severe bradycardia and a greater increase of pulmonary vascular resistance which might have contributed to the more pronounced reduction of CO. 4. PcGMP increased in both groups following L-NAME, but more (P < 0.01) in NP than P rabbits. 5. Infusion of acetylcholine (ACh, 0.02 micromol l-1 kg-1) reduced MAP and TPR more (both P < 0.05) in NP than P rabbits and L-NAME reduced the ACh-induced depressor response only in NP rabbits. 6. These results suggest that the low vascular tone and arterial pressure in pregnant rabbits is not mediated by NO.
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PMID:The vasoconstrictor effects of L-NAME, a nitric oxide synthase inhibitor, in pregnant rabbits. 879 76

1. RR may act as a preferential capsaicin antagonist in the pig nasal mucosa in vivo. However, the present data reveal a narrow concentration range for the selective actions of RR. Moreover, RR has systemic cardiovascular side effects despite local i.a. infusion in the IMA. 2. Acoustic rhinometry is a useful method for investigations of changes in nasal cavity volume in the pig in vivo. 3. The NK1-receptor antagonist RP-67,580 lacks NK1-receptor blocking properties in the pig in vivo. In contrast, CP-96,345 and SR 140.333 significantly blocked SP-mediated vascular effects in the pig nasal mucosa and superficial skin, indicating species dependent NK1-receptor selectivity. Capsaicin-induced vasodilatation in the IMA was not attenuated after administration of CP-96,345 and SR 140.333 whereas the superficial blood flow in the nasal mucosa and skin was slightly reduced. The CGRP-receptor antagonist hCGRP 8-37 markedly reduced the capsaicin-evoked vascular effects in the pig nasal mucosa and superficial skin. 4. Vanilloid receptors, as revealed by 3H-RTX binding, are present in the pig nasal mucosa although with different characteristics compared to vanilloid receptors in the pig dorsal horn. Capsaicin, RTX and LA evoked vasodilatation in the pig nasal mucosa in a similar fashion, indicating activation of sensory nerves. The LA (proton)-evoked vasodilatation was significantly attenuated after local i.a. infusion of hCGRP 8-37, closely resembling the results obtained from the capsaicin challenge before and after CGRP-receptor blockade. Capsazepine did not reduce the capsaicin-and LA-evoked vasodilation in the pig nasal mucosa. This agrees well with the observation that capsazepine did not inhibit RTX binding to vanilloid receptors in pig nasal mucosal membranes. 5. Capsaicin desensitisation of the human nasal mucosa attenuated the subjective pain response as well as the reduction of the cross-sectional area in the nasal cavity evoked by LA and hypertonic saline. This finding gives further support to the hypothesis that protons may act as endogenous ligands to the vanilloid receptor also in man. 6. Systemic administration of the NOS inhibitor L-NNA significantly reduced basal nasal V Con and increased C Vol in the pig. The effects evoked by L-NNA were similar in magnitude to those of phenylephrine and UK 14304, although of much longer duration. Administration of L-NNA did not reduce the vasodilator responses to SP and ACh, suggesting that these substances may mediate their vascular effects via one or several other mechanisms beside the NO/cGMP pathway. Moreover, capsaicin-, VIP-, and nitroprusside-evoked vasodilatation was not reduced after NOS inhibition. 7. Heavy physical exercise and alpha-adrenoceptor agonists reduce nasal cavity NO levels acutely in man. This may be due to a reduced supply of substrates for NO synthesis in the paranasal sinus epithelium, the primary NO production site in the upper airways. However, prolonged use of the alpha 2-adrenoceptor agonist oxymetazoline for 10 days, did not reduce basal nasal cavity NO levels. Nasal cavity NO levels and C Vol were not altered after topical administration of the NOS inhibitor L-NAME. Nor did we see any change in C Vol after local challenge with NO gas in the nasal cavity. The present results indicate that the human nasal mucosa is largely insensitive to NO gas in contrast to the bronchial mucosa and lung. 9. In conclusion, the present results suggest that vanilloid receptors are present on sensory nerves in the pig nasal mucosa and that LA (protons) may act as an endogenous ligand to this receptor. Sensory neuropeptides, especially CGRP, may be of importance for nasal congestion upon sensory nerve activation. Hence, selective, non-peptide CGRP-receptor antagonists may be of potential use in nasal disorders characterised by nasal congestion. NO is of importance for basal nasal vascular regulation. However, whether NOS inhibitors have potential as useful nasal de
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PMID:Sensory neuropeptides and nitric oxide in nasal vascular regulation. 880 Mar 74

Using L-NAME and the potassium channel blocker apamin we have investigated the component of acetylcholine-induced vascular relaxation lost when the mesenteric arterial bed is denervated. We have confirmed that vascular denervation produces a reduction of up to 35% in the ability of ACh to cause relaxation in the presence of the alpha agonists methoxamine and cirazoline. A single 30 minute exposure to L-NAME reduced the relaxation to ACh by up to 44% in control vascular preparations and by 85% in denervated preparations. In control preparations, prolonged exposure to L-NAME reduced the relaxation to ACh by up to 66% and by 77% in the presence of apamin. In denervated preparations prolonged exposure to L-NAME reduced the relaxation to ACh by 96%. The almost complete loss of acetylcholine-induced relaxation following prolonged exposure to L-NAME (96.6% in methoxamine and 93.9% in cirazoline) in denervated preparations suggests that innervation is involved in the expression of the L-NAME-resistant relaxation to acetylcholine in the superior mesenteric arterial bed of the rat.
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PMID:The L-name-resistant component of acetylcholine-induced relaxation of the rat superior mesenteric arterial bed is innervation-dependent. 882 97

1. We assessed whether a submaximal concentration (1 microM) of 5-hydroxytryptamine (5-HT) releases nitric oxide (NO) from the coronary endothelium in guinea-pig perfused heart (n = 5 or 6/group) by direct detection of NO in coronary effluent, and determined whether this accounts for the associated coronary dilation. We also tested whether saponin is a selective and specific tool for examining the role of this mechanism in mediating agonist-induced coronary dilatation. 2. Continuous 5 min perfusion with 5-HT, or acetylcholine (ACh; 1 microM), substance P (1 nM) or sodium nitroprusside (SNP; 1 microM) increased coronary flow from baseline by 3.6 +/- 0.2, 3.4 +/- 0.2, 1.8 +/- 0.1 and 4.1 +/- 0.2 ml min-1 g-1, respectively (all P < 0.05). Coronary effluent NO content, detected by chemiluminescence, was correspondingly increased from baseline by 715 +/- 85, 920 +/- 136, 1019 +/- 58 and 2333 +/- 114 pmol min-1 g-1, respectively (all P < 0.05). 3. Continuous perfusion for 30 min with NG-nitro-L-arginine methyl ester (L-NAME) 100 microM reduced basal coronary effluent NO content by 370 +/- 32 pmol min-1 g-1 and coronary flow by 7.5 +/- 0.5 ml min-1 g-1 (both P < 0.05). Saponin (three cycles of 2 min of 30 micrograms ml-1 saponin perfusion interrupted by 2 min control perfusion) reduced basal coronary NO content by a similar amount (307 +/- 22 pmol min-1 g-1) but reduced basal coronary flow by only 0.6 +/- 0.2 ml min-1 g-1 (P < 0.05 versus the effect of L-NAME). 4. The increases in coronary flow in response to (5-HT), ACh and substance P were reduced (all P < 0.05) by 100 microM L-NAME to 1.2 +/- 0.3, 1.2 +/- 0.4 and 0.3 +/- 0.3 ml min-1 g-1, respectively. However, the flow increase in response to SNP was not reduced; it was in fact increased slightly to 4.8 +/- 0.4 ml min-1 g-1 (P < 0.05). 5. Similarly, after treatment with saponin, the increases in coronary flow in response to 5-HT, ACh and substance P were reduced to 2.1 +/- 0.3, 1.3 +/- 0.3 and 0.4 +/- 0.2 ml min-1 g-1, respectively (all P < 0.05). Again, the response to SNP was increased slightly to 4.6 +/- 0.5 ml min-1 g-1 (P < 0.05). 6. L-NAME and saponin also inhibited 5-HT, ACh and substance P-induced NO release (P < 0.05), without affecting equivalent responses to SNP. 7. For substance P, the change in coronary flow (delta CF) correlated with log10 delta NO in the presence and absence of saponin and L-NAME; delta CF = 1.2(log delta NO) 1.9; r = 0.92; P < 0.05. For 5-HT the relationship was delta CF = 2.2(log delta NO-2.7; r = 0.79; P < 0.05, indicating that 5-HT causes a disproportionately greater increase in coronary flow per release of NO. This was taken to indicate that 5-HT relaxes coronary vasculature in part by releasing NO, but in part by additional mechanisms. ACh resembled 5-HT in this respect. 8. Saponin had no effect on cardiac systolic or diastolic contractile function assessed by the construction of Starling curves with an isochoric intraventricular balloon. 9. In conclusion, despite its minimal effect on basal coronary flow, saponin is an effective tool for revealing endothelium-dependent actions of coronary vasodilator substances and has selectivity in that it does not impair endothelium-independent vasodilatation or cardiac contractile function. 5-HT dilates guinea-pig coronary arteries largely by the release of NO from the coronary endothelium.
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PMID:Mechanism of 5-hydroxytryptamine-induced coronary vasodilation assessed by direct detection of nitric oxide production in guinea-pig isolated heart. 890 47

1. Several previous in vivo studies demonstrated that crosslinked hemoglobin is a potent vasoconstrictor capable of significantly increasing arterial blood pressure following systemic administration. The precise mechanisms underlying the vascular effects of crosslinked hemoglobin are not clear. The present study was designed to determine the effect of crosslinked hemoglobin on the endothelial L-arginine-nitric oxide biosynthesis pathway in isolated canine arteries. 2. Isolated femoral and renal arteries were suspended in organ chambers for isometric tension recordings. Endothelium-dependent relaxations to acetylcholine and calcium ionophore A23187 were studied in the absence or in the presence of crosslinked hemoglobin or hemoglobin. A radioimmunoassay technique was used to determine levels of guanosine 3',5'-cyclic monophosphate (cyclic GMP) and adenosine 3',5'-cyclic monophosphate (cyclic AMP). 3. A nitric oxide synthase inhibitor L-NAME (10(-4)M) selectively inhibited endothelium-dependent relaxations to acetylcholine and calcium ionophore A23187. The inhibitory effect of L-NAME was reversed by L-arginine (3 x 10(-4)M). Crosslinked hemoglobin (10(-7), 10(-6) and 10(-5)M) inhibited endothelium-dependent relaxations to acetylcholine (10(-9)-10(-5)M) or A23187 (10(-9)-10(-6)M). In the same concentration range, purified bovine hemoglobin exerted a similar inhibitory effect on relaxations mediated by activation of endothelial cells. Crosslinked hemoglobin (10(-6)M) significantly reduced basal production of cyclic GMP, but did not affect production of cyclic AMP. Acetylcholine (10(-6)M) stimulated production of cyclic GMP. This effect of acetylcholine was abolished in the presence of crosslinked hemoglobin. 4. These studies demonstrate that crosslinked hemoglobin impairs endothelium-dependent relaxations in isolated large conduit arteries. This effect appears to be mediated by the chemical antagonism of crosslinked hemoglobin against nitric oxide released from the endothelium. Inhibition of the endothelial L-arginine-nitric oxide biosynthesis pathway, with subsequent decrease of cyclic GMP in smooth muscle, may help to explain vasoconstrictor and pressor effects of crosslinked hemoglobin.
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PMID:Crosslinked hemoglobin inhibits endothelium-dependent relaxations in isolated canine arteries. 891 36

The study was designed to assess the influence of nitric oxide (NO) on myocardial contractility in vivo. The left anterior descending coronary artery (LAD) of 28 anesthetized, open-chest dogs was perfused with arterial blood via an extracorporeal circuit. In the LAD bed, segmental shortening (SS), an index of local myocardial contractility, was measured with ultrasonic crystals. Coronary blood flow (CBF) was measured by Doppler flow transducer and used to calculate myocardial oxygen consumption (MVO2). Studies were performed with coronary perfusion pressure (CPP) constant (n = 23) or with CBF constant (n = 5). Measurements were obtained 1) during intracoronary infusions of the NO donors sodium nitroprusside (SNP, 80 ng/min) and nitroglycerin (NTG, 40 micrograms/min) and of a stimulator of endogenous NO release, acetylcholine (ACh, 20 micrograms/min), and 2) after inhibition of basal NO synthase activity with either NG-nitro-L-arginine methyl ester (L-NAME, 300 micrograms/min ic for 15 min) or NG-monomethyl-L-arginine (L-NMMA 2mg/min ic for 15 min). Decreases in SS (-38%) and MVO2 (-42%) during intracoronary isoflurane infusion verified responsiveness of preparation to negative inotropic agents. With CPP constant, SNP, NTG, and ACh caused increases in CBF (177, 28, and 280%, respectively) with no changes in SS or MVO2. Neither L-NAME nor L-NMMA affected SS, MVO2, or CBF. With CBF constant, the SNP- and ACh-induced decreases in CPP were accompanied by no changes in SS. In conclusion, NO had no direct influence on myocardial contractility or oxygen demand under baseline conditions, or when its local concentration was increased acutely with SNP, NTG, or ACh. An augmented SS secondary to increased CBF per se, i.e., Gregg's phenomenon, did not obscure potential negative inotropic effects of SNP and ACh with CPP constant.
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PMID:Nitric oxide does not modulate myocardial contractility acutely in in situ canine hearts. 892 61

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