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Anwar MA, Ford WR, Broadley KJ, Herbert AA. Vasoconstrictor and vasodilator responses to tryptamine of rat-isolated perfused mesentery: comparison with tyramine and β-phenylethylamine. Br J Pharmacol 2012; 165:2191-202. [PMID: 21958009 PMCID: PMC3413856 DOI: 10.1111/j.1476-5381.2011.01706.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Tryptamine increases blood pressure by vasoconstriction, but little is known about its actions on the mesentery, in particular the resistance arteries. Tryptamine interacts with trace amine-associated receptors (TAARs) and because of its structural similarity to 5-HT, it may also interact with 5-HT receptors. Our hypothesis is therefore that the rat mesenteric arterial bed will exhibit vasopressor and vasodepressor responses to tryptamine via both 5-HT and TAARs. EXPERIMENTAL APPROACH Tryptamine-evoked responses were assayed from pressure changes of the rat-isolated mesenteric vasculature perfused at constant flow rate in the absence and presence of adrenoceptor and 5-HT receptor antagonists. KEY RESULTS Tryptamine caused dose-dependent vasoconstriction of the mesenteric arterial bed as increases in perfusion pressure. These were unaffected by the α1-adrenoceptor antagonist, prazosin, but were attenuated by the non-selective α-adrenoceptor antagonist, phentolamine. The 5-HT2A receptor antagonists, ketanserin and ritanserin, abolished the tryptamine-induced pressure increases to reveal vasodilator responses in mesenteric beds preconstricted with phenylephrine. These tryptamine-induced vasodilator responses were unaffected by the 5-HT7 receptor antagonist, SB269970, but were eliminated by the NOS inhibitor, Nω-nitro-L-arginine methyl ester (L-NAME). Tyramine and β-phenylethylamine also caused vasodilatation in pre-constricted vasculature, which was also abolished by L-NAME. CONCLUSIONS AND IMPLICATIONS Tryptamine causes vasoconstriction of the mesenteric vasculature via 5-HT2A receptors, which when inhibited exposed vasorelaxant effects in pre-constricted tissues. The vasodilatation was independent of 5-HT2A and 5-HT7 receptors but like that for tyramine and β-phenylethylamine was due to NO release. Potency orders suggest TAAR involvement in the vasodilatation by these trace amines.
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Affiliation(s)
- M A Anwar
- Division of Pharmacology, Welsh School of Pharmacy, Cardiff University, Cardiff, UK
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2
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Tzirogiannis KN, Demonakou MD, Papadimas GK, Skaltsas SD, Manta GA, Kourentzi KT, Alexandropoulou KN, Hereti RI, Mykoniatis MG, Panoutsopoulos GI. Effect of 5-HT(2) receptor blockade on cadmium-induced acute toxicity. Dig Dis Sci 2007; 52:2351-8. [PMID: 17420952 DOI: 10.1007/s10620-006-9132-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Accepted: 11/08/2005] [Indexed: 12/09/2022]
Abstract
The protective effect of 5-HT(2) receptor blockade with ketanserin or ritanserin against cadmium liver injury was investigated. Male Wistar rats were injected intraperitoneally with a sublethal dose of cadmium (3.5 mg/kg body weight). Rats were treated with normal saline (group I), ketanserin (3 mg/kg body weight; group II), or ritanserin (3 mg/kg body weight; group III) 2 hr prior and 4 hr after cadmium administration and killed at different time points. Hematoxylin/eosin-stained liver sections were assessed for necrosis, apoptosis, peliosis, mitoses, and inflammatory infiltration. Apoptosis was also quantified by the TUNEL assay. Nonparenchymal liver cells and activated Kupffer cells were identified histochemically. Necrosis, hepatocyte apoptosis, nonparenchymal cell apoptosis, and macroscopic and microscopic peliosis were markedly reduced or minimized in ketanserin- or ritanserin-treated rats. The observed protective effect was almost identical for both ketanserin and ritanserin administration. 5-HT(2) receptor blockade exerts a protective effect against acute cadmium-induced hepatotoxicity.
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Affiliation(s)
- Konstantinos N Tzirogiannis
- Department of Experimental Pharmacology, Medical School, Athens University, 75 Mikras Asias Street, Athens 11527, Greece
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Grundy D, McLean P, Stead R. Impact of 5-HT3 receptor blockade on colonic haemodynamic responses to ischaemia and reperfusion in the rat. Neurogastroenterol Motil 2007; 19:607-16. [PMID: 17593142 DOI: 10.1111/j.1365-2982.2007.00938.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
5-HT(3) receptor antagonists are clinically available for treating patients with irritable bowel syndrome (IBS) but their use is restricted because of a link with some episodes of ischaemic colitis. However, the role of 5-HT3 receptors in regulating colonic blood flow has not been systematically investigated. Thus, we examined acute and chronic treatment with alosetron, a potent and selective antagonist of the 5-HT3 receptor, on baseline colonic blood flow and haemodynamic responses during occlusion and reactive hyperaemia in the pentobarbitone-anaesthetized rat. Colonic haemodynamics were assessed using ultrasonic recordings of superior mesenteric blood flow (MBF) and laser Doppler recordings of colonic vascular perfusion (VP). Blood pressure (BP) was also monitored and in some experiments tissue oxygen was detected polarographically. Alosetron (10, 30, 100 microg kg(-1), i.v.) had no effect on baseline haemodynamics nor responses to nitric oxide synthase inhibition with N(omega)-nitro-l-arginine methyl ester (l-NAME) (16 mg kg(-1)). Arterial occlusion (5 min) reduced MBF (-98.6 +/- 0.6%) and VP (-70.7 +/- 5.4%) followed by a post-occlusion reactive hyperaemia (MBF = +94.5 +/- 19.1%; VP = +60.0 +/- 22.3%) the magnitude of which was unchanged following acute (30 microg kg(-1)) or chronic alosetron administration (0.5 mg kg(-1) twice daily, 5 days). Alosetron did not significantly alter baseline colonic blood flow in the anaesthetized rat; nor did it interfere with vascular control mechanisms activated during occlusion and reactive hyperaemia.
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Affiliation(s)
- D Grundy
- Department of Biomedical Science, The University of Sheffield, Sheffield, UK.
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Hansen MB, Arif F, Wallin L, Pedersen JF. Serotonin and superior mesenteric artery resistance index. Scandinavian Journal of Clinical and Laboratory Investigation 2007; 66:395-406. [PMID: 16901850 DOI: 10.1080/00365510600763301] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
OBJECTIVE Serotonin is a vasoactive neuroendocrine substance and serotonergic drugs are promising agents for the treatment of functional gastrointestinal disorders. The effect of serotonin on superior mesenteric blood flow in humans is unknown. The aim of this study was to examine the effect of exogenous serotonin on superior mesenteric artery blood flow, as estimated by the resistance index with Doppler ultrasound, in healthy human volunteers. MATERIAL AND METHODS Six fasting healthy adult volunteers of both genders were studied. Transabdominal Doppler ultrasound was used to evaluate the effects of either a standard meal or intravenous infusion of serotonin (2.5-20 nmol kg-1 min-1) on the superior mesenteric artery resistance index, platelet-depleted plasma levels of serotonin, blood pressure, heart rate and electrocardiogram. RESULTS All subjects had the same patterns of response to meal and serotonin stimulation. Meal stimulation decreased the mean resistance index from 0.84+/-0.04 to 0.72+/-0.02 (p = 0.0004) and increased platelet-depleted-plasma levels of serotonin from 50+/-36 to 61+/-46 nmol L-1 (p = 0.04). Serotonin stimulation increased the mean resistance index from 0.82+/-0.04 to 0.88+/-0.03 (p = 0.006) and mean platelet-depleted-plasma levels of serotonin from 44+/-24 to 83+/-37 nmol L-1 (p = 0.03). Most subjects reported minor short-lived adverse effects. Electrocardiogram results were unchanged during all examinations. CONCLUSIONS We conclude that intravenous infusion of serotonin increases the resistance index of the superior mesenteric artery (increases downstream resistance) in healthy adult volunteers.
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Affiliation(s)
- M B Hansen
- Department of Gastrointestinal Surgery, Glostrup University Hospital of Copenhagen, DK-2600 Glostrup, Denmark.
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McHale NG, Thornbury KD, Hollywood MA. 5-HT inhibits spontaneous contractility of isolated sheep mesenteric lymphatics via activation of 5-HT(4) receptors. Microvasc Res 2000; 60:261-8. [PMID: 11078642 DOI: 10.1006/mvre.2000.2275] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spontaneous isometric contractions were measured in rings of sheep mesenteric lymphatic vessels in vitro. 5-Hydroxytryptamine (5-HT) produced a concentration-dependent decrease in spontaneous contraction frequency and force which was not antagonised by either the nonspecific 5-HT(1)/5-HT(2) receptor antagonist methysergide (1 microM) or the 5-HT(3) receptor antagonist ondansetron (1 microM). The 5-HT(4) receptor agonist BIMU-8 mimicked the inhibitory effect of 5-HT and its effects were abolished by the 5-HT(4) receptor antagonist DAU 6285 (1 microM). DAU-6285 also abolished the inhibitory effect of 5-HT and unmasked a weak excitatory response, which was mimicked by the 5-HT(2) receptor agonist alpha-methyl-5-hydroxytryptamine maleate. This excitatory response was, in turn, blocked by the 5-HT(2) receptor antagonist pirenperone (1 microM). The results of this study suggest that sheep mesenteric lymphatics possess both 5-HT(4) receptors and 5-HT(2) receptors. The inhibitory 5-HT(4) receptor appeared to be the predominant subtype since the excitatory response to 5-HT could only be observed in the presence of the 5-HT(4) receptor antagonist DAU 6285.
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Affiliation(s)
- N G McHale
- Smooth Muscle Group, Department of Physiology, Queen's University, 97 Lisburn Road, Belfast, BT9 7BL, Northern Ireland
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Bruning TA, Chang PC, Blauw GJ, Vermeij P, Van Zwieten PA. Interactions between serotonin and endogenous and exogenous noradrenaline in the human forearm. Blood Press 1994; 3:309-18. [PMID: 7866595 DOI: 10.3109/08037059409102279] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We investigated the interactions between serotonin (5-hydroxytryptamine, 5-HT) and exogenous or endogenous noradrenaline (NA) in the forearm of normotensive volunteers (n = 24), using venous occlusion plethysmography. Endogenous release of NA was stimulated by lower body negative pressure (LBNP; -10, -20 and -40 mmHg) and by intra-arterial (i.a.) infusions of tyramine (0.1 to 1 microgram/kg/min). Exogenous NA was infused in cumulative doses (0.3 to 10 ng/kg/min). All experiments were performed in the presence of either vehicle (0.4 mL/min), sodium nitroprusside (SNP; 3 or 5 ng/kg/min), or 5-HT (0.1 or 1 ng/kg/min). NA or 5-HT (1 ng/kg/min) were also infused with the selective 5-HT2 receptor antagonist ritanserin (500 ng/kg/min). Angiotensin II (Ang II; 0.03 to 0.3 ng/kg/min) was given as a vasoconstrictor control (n = 6). Vasoconstriction to exogenous NA was significantly enhanced by 5-HT (1 ng/kg/min; p < 0.05) in one group of subjects, but this could not be reproduced in a second group. In contrast, the vasoconstrictor responses to endogenous NA remained unaffected by 5-HT. SNP caused the same degree of vasodilation as 5-HT, and was followed by a similar response to NA. Ritanserin did not alter the vasoconstriction to infused NA, nor vasoconstriction to infused NA when combined with 5-HT. The vasoconstrictor response to Ang II was not influenced by 5-HT (0.1 ng/kg/min). Apparently, a synergistic effect between 5-HT and NA in the periphery involves a nonspecific mechanism. The latter seems to be confined to infused NA. The precise role of the 5-HT2 receptor in this interaction could not be elucidated.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- T A Bruning
- Department of Nephrology, University Hospital, Leiden, The Netherlands
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7
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Abstract
The complex actions of 5-hydroxytryptamine (5-HT) on blood vessels result from interactions with a multiplicity of specific 5-HT receptors. Dramatic advances recently have been made in defining the receptor subtypes involved in terms of their pharmacology and biochemistry, as well as their molecular biology, provoking an evolution of the criteria used for classifying and naming them. This article reviews the distribution and function of different 5-HT receptor types present on vascular smooth muscle, endothelium and perivascular neurones, and considers ways in which they can be positively defined and differentiated using traditional pharmacological approaches. The characteristics of each receptor type are also considered in terms of current biochemical and molecular perspectives on 5-HT receptor classification.
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Affiliation(s)
- G R Martin
- Analytical Pharmacology Group, Wellcome Research Laboratories, Beckenham, Kent, U.K
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Abstract
1. The present review discusses evidence in support of the concept that alterations in sympathetic neurotransmitter release might contribute to the pathogenesis of hypertension. 2. Studies suggest that changes in sympathetic nervous activity in both the central and peripheral nervous systems participate in blood pressure control. 3. In the periphery increased release of norepinephrine from vascular adrenergic neurons might lead to the enhanced vasoconstrictor responses and thus to an elevation in systemic blood pressure. 4. The amount of neurotransmitter release from sympathetic nerve endings can be regulated by autoregulatory systems by presynaptic receptors located on nerve terminals. 5. It has been proposed that alterations to sympathetic nervous activity of hypertension might be partially due to abnormalities in presynaptic modulation of neurotransmitter release in central and peripheral tissues. 6. This article summarizes the results of studies to evaluate presynaptic receptor functions and sympathetic neurotransmitter release in hypertension.
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Affiliation(s)
- K Tsuda
- Department of Medicine, Wakayama Medical College, Japan
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Barrús MT, Balfagón G, Salaíces M, Marín J. [3H]5-hydroxytryptamine uptake and release in cat cerebral arteries. GENERAL PHARMACOLOGY 1990; 21:189-94. [PMID: 2332139 DOI: 10.1016/0306-3623(90)90899-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1. Field electrical stimulation induced tritium release from cat cerebral arteries preincubated with [3H]serotonin (5-HT). 2. This release was markedly reduced by tetrodotoxin (0.8 microM), B-HT 920 (1 microM), denervation with 6-OH-dopamine (6-OHDA) and OCa2+, and increased by phentolamine (1 microM) and phorbol 12,13-dibutyrate (1 and 3 microM). 3. 5-HT (10 and 100 microM) and NA (0.1, 1 and 10 microM) caused concentration-dependent tritium release in control arteries, but not in those denervated with 6-OHDA. 4. [3H]5-HT uptake was greatly reduced by preincubation of arteries with cocaine (10 microM), ouabain (100 microM) or denervation with 6-OHDA. 5. 5-HT did not amplify contractions elicited by noradrenaline (NA) in middle cerebral arteries. 6. These data indicate: (1) 5-HT is mainly accumulated in adrenergic nerve endings; (2) 5-HT release is modulated by presynaptic alpha 2-adrenoceptors; (3) protein kinase C of perivascular adrenergic nerve endings participates in 5-HT release, and (4) 5-HT did not amplify NA responses.
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Affiliation(s)
- M T Barrús
- Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma, Madrid, Spain
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10
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Xiao XH, Rand MJ. Amplification by serotonin of responses to other vasoconstrictor agents in the rat tail artery. Clin Exp Pharmacol Physiol 1989; 16:725-36. [PMID: 2805436 DOI: 10.1111/j.1440-1681.1989.tb01627.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
1. A low concentration of serotonin (3 nmol/L), which did not exert a direct vasoconstrictor action, amplified the responses to certain other vasoconstrictor agents (alpha 1-adrenoceptor agonists, KCl, ATP and vasopressin) in isolated perfused segments of the rat tail artery. 2. Low concentrations of serotonin (0.3 and 1 nmol/L) amplified vasoconstrictor responses to sympathetic nerve stimulation, but higher concentrations of serotonin (10 and 30 nmol/L) produced vasoconstriction and reduced responses to sympathetic nerve stimulation. 3. The calcium channel blocking drug diltiazem (1 and 10 mumol/L) produced concentration-dependent reductions of vasoconstrictor responses to phenylephrine. The amplifying effect of serotonin on responses to phenylephrine was attenuated by 1 mumol/L and abolished by 10 mumol/L diltiazem, and was also abolished in a Ca2+-free medium. 4. Ketanserin (10 nmol/L) antagonized the vasoconstrictor action of serotonin and, to a lesser extent, the vasoconstrictor actions of phenylephrine and noradrenaline. It abolished the amplifying effect of a low concentration of serotonin on responses to noradrenaline and phenylephrine. 5. The amplification of vasoconstrictor response in the rat tail artery by serotonin appears to be due to activation of receptors of the 5-HT2 subtype which are coupled to an increase in Ca2+ influx into the vascular smooth muscle cells.
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Affiliation(s)
- X H Xiao
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia
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11
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Molderings GJ, Göthert M, Fink K, Roth E, Schlicker E. Inhibition of noradrenaline release in the pig coronary artery via a novel serotonin receptor. Eur J Pharmacol 1989; 164:213-22. [PMID: 2759173 DOI: 10.1016/0014-2999(89)90461-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In pig coronary artery preincubated with [3H]noradrenaline, the effects of serotonin (5-HT) receptor agonists and antagonists on the electrically evoked (0.66 Hz) tritium overflow were determined. Tritium overflow was inhibited by 5-HT, 5-aminotryptamine, N,N-dimethyl-5-hydroxytryptamine, 5-hydroxytryptamine, 5-methoxy-3(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole (RU 24969) and tryptamine. The maximum inhibition obtainable with 5-HT was by about 35%, its pIC20 value was 7.85. 8-Hydroxy-di(n-propylamino)tetralin, urapidil, ipsapirone, 5-carboxamidotryptamine, 4-hydroxytryptamine, 5-methoxytryptamine and alpha-methyl-5-hydroxytryptamine did not decrease 3H overflow. The inhibitory effect of 5-HT was not antagonized by ketanserin, mesulergine, metitepine, propranolol, (3 alpha-tropanyl)-1H-indole-3-carboxylic acid ester (ICS 205-930) and yohimbine. Additionally, it was not altered by indomethacin. We conclude from the present data that the sympathetic nerves of the pig coronary artery are endowed with inhibitory presynaptic 5-HT receptors which do not belong to the 5-HT1, 5-HT2 or 5-HT3 receptor type but seem to represent a so far unknown receptor class.
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Affiliation(s)
- G J Molderings
- Institute of Pharmacology and Toxicology, Rheinische Friedrich-Wilhelms-Universität Bonn, F.R.G
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12
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Meehan AG, Medgett IC, Story DF. Involvement of Ca2+ mobilization in the amplifying effect of serotonin on responses of rabbit isolated ear artery to exogenous noradrenaline. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1988; 337:500-3. [PMID: 3412490 DOI: 10.1007/bf00182722] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The present study examined the involvement of Ca2+ mobilization in the amplifying effect of serotonin on steady-state responses of rabbit isolated perfused ear artery to exogenous noradrenaline (NA; 0.001-3 mumol/l). In contrast to its marked amplifying effect on responses to NA, serotonin in the subconstrictor concentration of 100 nmol/l had no effect on responses to KCl. The Ca2+-entry blocking drug diltiazem (10 mumol/l) decreased responses to NA; in addition, the amplifying effect of serotonin on responses to NA was reduced by diltiazem. Lowering the concentration of Ca2+ in the Krebs-Henseleit perfusion solution from 2.5 to 0.25 mmol/l also reduced both responses to NA and the amplifying effect of serotonin. Using the method of Manzini et al. (1982), separate intra- and extracellular Ca2+-dependent responses to NA were obtained. Serotonin had no effect on intracellular Ca2+-dependent responses to NA but enhanced extracellular Ca2+-dependent NA responses. These results suggest that the amplifying effect of serotonin on responses of rabbit ear artery to exogenous NA involves a selective enhancement of the component of the NA response which is dependent on extracellular Ca2+; serotonin may increase NA-evoked entry of Ca2+ into the vascular smooth muscle cells through receptor-operated Ca2+ channels.
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Affiliation(s)
- A G Meehan
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia
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13
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Molderings GJ, Fink K, Schlicker E, Göthert M. Inhibition of noradrenaline release via presynaptic 5-HT1B receptors of the rat vena cava. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1987; 336:245-50. [PMID: 3683595 DOI: 10.1007/bf00172673] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In the rat inferior vena cava preincubated with 3H-noradrenaline, the effects of nine serotonin (5-HT) receptor agonists and of eight antagonists (including two beta-adrenoceptor blocking agents) on the electrically evoked 3H overflow were determined. 1. 5-HT, 5-carboxamido-tryptamine, 5-methoxy-3(1,2,3,6-tetrahydropyridine-4-yl)-1H-indole (RU 24969), 5-methoxytryptamine, N,N-dimethyl-5HT, tryptamine and 5-aminotryptamine inhibited the evoked 3H overflow. The potencies of these agonists in inhibiting overflow were significantly correlated with their affinities for 5-HT1B binding sites, but not with their affinities for 5-HT1A, 5-HT1C or 5-HT2 binding sites. 8-Hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a 5-HT1A receptor agonist, and ipsapirone, a partial agonist at these receptors, did not inhibit overflow. 2. Cyanopindolol facilitated the evoked 3H overflow, an effect which was abolished by propranolol. The maximum inhibition of overflow obtainable with 5-HT was diminished by cyanopindolol. 3. The concentration-response curve for 5-HT was shifted to the right by metitepine, metergoline, quipazine, 6-chloro-2-(1-piperazinyl)pyrazine (MK 212) and propranolol which, given alone, did not affect 3H overflow. The apparent pA2 values of these antagonists tended to be correlated with their affinities for 5-HT1B (but not 5-HT1A, 5-HT1C or 5-HT2) binding sites. Ketanserin, a 5-HT2 receptor antagonist, and spiperone, which blocks 5-HT2 and 5-HT1A but not 5-HT1B or 5-HT1C receptors, failed to antagonize the effect of 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G J Molderings
- Institut für Pharmakologie und Toxikologie der Rheinischen Friedrich-Wilhelms-Universität Bonn, Federal Republic of Germany
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Moritoki H, Fukuda H, Kanaya J, Ishida Y. Ketanserin potentiates the prejunctional inhibitory effect of 5-hydroxytryptamine on rat vas deferens. J Pharm Pharmacol 1986; 38:737-41. [PMID: 2878993 DOI: 10.1111/j.2042-7158.1986.tb04481.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
5-Hydroxytryptamine (5-HT) slightly inhibited the twitch contractions of rat vas deferens caused by single pulse field stimulation at 0.1 Hz. The inhibitory effect of 5-HT was much less in the epididymal portion than in the prostatic portion of the vas deferens. Ketanserin potentiated the prejunctional inhibitory effect of 5-HT and attenuated its stimulatory effect. This potentiation was observable only in the epididymal portion, of the vas deferens. Cyproheptadine and mianserin, but not methysergide, had essentially similar potentiating effects to those of ketanserin. These results suggest that the 5-HT receptor that mediates prejunctional inhibition is not of the 5-HT2 type, and that ketanserin acts by suppressing the 5-HT-induced stimulatory effect, which is possibly mediated by a postjunctional 5-HT2 receptor, thus unmasking the inhibitory effect of 5-HT.
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15
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Göthert M, Schlicker E, Kollecker P. Receptor-mediated effects of serotonin and 5-methoxytryptamine on noradrenaline release in the rat vena cava and in the heart of the pithed rat. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1986; 332:124-30. [PMID: 2939353 DOI: 10.1007/bf00511401] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In segments of the rat inferior vena cava preincubated with 3H-noradrenaline, it was examined whether presynaptic serotonin (5-HT) receptors exist on the postganglionic sympathetic nerves of the circulatory system; for this purpose the effects of 5-HT receptor agonists and antagonists on the electrically evoked 3H overflow were studied. Furthermore, vagotomized pithed rats (treated with atropine and captopril) were used to investigate the effects of these drugs on heart rate and on the tachycardia induced by electrical stimulation of the preganglionic sympathetic nerves (C7--T1) via the pithing rod; these experiments were carried out to provide evidence that the presynaptic 5-HT receptors are operative in vivo. 5-HT and 5-methoxytryptamine (5-OCH3-T) concentration-dependently inhibited the electrically evoked 3H overflow from the vena cava. The inhibitory effect was more pronounced at 0.66 Hz than at 2 Hz. 8-Hydroxy-2-(di-n-propylamino)tetralin did not alter the evoked overflow. The inhibitory effect of 5-HT or 5-OCH3-T was antagonized by metitepin but not affected by ketanserin or rauwolscine. In pithed rats 5-HT and 5-OCH3-T by themselves dose-dependently increased heart rate. The positive chronotropic effect of 5-HT 10 mumol/kg, which was not affected by ketanserin, was considerably decreased by desipramine, indicating that 5-HT at least at this high dose acts predominantly by a tyramine-like indirect sympathomimetic effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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