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Fuder H, Muscholl E. Heteroreceptor-mediated modulation of noradrenaline and acetylcholine release from peripheral nerves. Rev Physiol Biochem Pharmacol 2006; 126:265-412. [PMID: 7886380 DOI: 10.1007/bfb0049778] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- H Fuder
- IKP-AKP, Professo Lücker GmbH, Grünstadt, Germany
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Ghildyal P, Palani D, Manchanda R. Post- and prejunctional consequences of ecto-ATPase inhibition: electrical and contractile studies in guinea-pig vas deferens. J Physiol 2006; 575:469-80. [PMID: 16675493 PMCID: PMC1819469 DOI: 10.1113/jphysiol.2006.109678] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
At sites of purinergic neurotransmission, synaptic ecto-ATPase is believed to limit the actions of ATP following its neural release. However, details of the modulation by this enzyme of the ATP-mediated conductance change and the possible mechanisms mediating this modulation remain unelucidated. We have addressed these issues by studying the effect of ARL 67156, a selective ecto-ATPase inhibitor, on ATP-mediated electrical and contractile activity in the sympathetically innervated guinea-pig vas deferens. ARL 67156 at 100 mum significantly potentiated the amplitude of spontaneous excitatory junction potentials (SEJPs) by 81.1% (P < 0.01) and prolonged their time courses (rise time by 49.7%, decay time constant by 38.2%; P < 0.01). Moreover, the frequency of occurrence of SEJPs was strikingly increased (from 0.28 +/- 0.13 to 0.90 +/- 0.26 Hz; P < 0.01), indicating an additional, primarily presynaptic, effect of ecto-ATPase inhibition. The frequency of occurrence of discrete events (DEs), which represent nerve stimulation-evoked quantal release of neurotransmitter, was also increased ( approximately 6-fold; P < 0.01), along with the appearance of DEs at previously 'silent' latencies. Purinergic contractions of the vas deferens were potentiated significantly (P < 0.01) by ARL 67156; these potentiated contractions were suppressed by the A1 agonist adenosine (P < 0.01) but left unaffected by the A1 antagonist 8-phenyltheophylline (8-PT). Our results indicate (i) that ecto-ATPase activity, in addition to modulating the ATP-mediated postjunctional conductance change, may regulate transmitter release prejunctionally under physiological conditions, and (ii) that the prejunctional regulation may be mediated primarily via presynaptic P2X, rather than A1, receptors.
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Affiliation(s)
- P Ghildyal
- Biomedical Engineering Group, School of Biosciences and Bioengineering, Indian Institute of Technology--Bombay, Mumbai 400076, India
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Trendelenburg AU, Cox SL, Schelb V, Klebroff W, Khairallah L, Starke K. Modulation of (3)H-noradrenaline release by presynaptic opioid, cannabinoid and bradykinin receptors and beta-adrenoceptors in mouse tissues. Br J Pharmacol 2000; 130:321-30. [PMID: 10807669 PMCID: PMC1572066 DOI: 10.1038/sj.bjp.0703305] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Release-modulating opioid and cannabinoid (CB) receptors, beta-adrenoceptors and bradykinin receptors at noradrenergic axons were studied in mouse tissues (occipito-parietal cortex, heart atria, vas deferens and spleen) preincubated with (3)H-noradrenaline. Experiments using the OP(1) receptor-selective agonists DPDPE and DSLET, the OP(2)-selective agonists U50488H and U69593, the OP(3)-selective agonist DAMGO, the ORL(1) receptor-selective agonist nociceptin, and a number of selective antagonists showed that the noradrenergic axons innervating the occipito-parietal cortex possess release-inhibiting OP(3) and ORL(1) receptors, those innervating atria OP(1), ORL(1) and possibly OP(3) receptors, and those innervating the vas deferens all four opioid receptor types. Experiments using the non-selective CB agonists WIN 55,212-2 and CP 55,940 and the CB(1)-selective antagonist SR 141716A indicated that the noradrenergic axons of the vas deferens possess release-inhibiting CB(1) receptors. Presynaptic CB receptors were not found in the occipito-parietal cortex, in atria or in the spleen. Experiments using the non-selective beta-adrenoceptor agonist isoprenaline and the beta(2)-selective agonist salbutamol, as well as subtype-selective antagonists, demonstrated the occurrence of release-enhancing beta(2)-adrenoceptors at the sympathetic axons of atria and the spleen, but demonstrated their absence in the occipito-parietal cortex and the vas deferens. Experiments with bradykinin and the B(2)-selective antagonist Hoe 140 showed the operation of release-enhancing B(2) receptors at the sympathetic axons of atria, the vas deferens and the spleen, but showed their absence in the occipito-parietal cortex. The experiments document a number of new presynaptic receptor locations. They confirm and extend the existence of marked tissue and species differences in presynaptic receptors at noradrenergic neurons.
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Affiliation(s)
- A U Trendelenburg
- Pharmakologisches Institut, Universität Freiburg, Hermann-Herder-Strasse 5, D-79104 Freiburg i. Br., Germany.
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O'Connor SC, Brain KL, Bennett MR. Individual sympathetic varicosities possess different sensitivities to alpha 2 and P2 receptor agonists and antagonists in mouse vas deferens. Br J Pharmacol 1999; 128:1739-53. [PMID: 10588930 PMCID: PMC1571817 DOI: 10.1038/sj.bjp.0702984] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The diversity of alpha(2) and purinergic autoreceptor actions on action potential evoked calcium transients in single varicosities has been investigated using the calcium indicator Oregon Green 488 BAPTA-1. 2. During long trains of impulses (10 Hz for 30 s), the change in calcium concentration in varicosities from its resting level (Delta[Ca(2+)](v)) increased in many varicosities during the first 3 s of stimulation before reaching a plateau. 3. The alpha(2) adrenoceptor agonist clonidine (1 microM) decreased Delta[Ca(2+)](v) by over 40% during short trains (five impulses at 5 Hz) in most varicosities, although some were unaffected. The alpha(2) adrenoceptor antagonist idazoxan (2 microM) increased the Delta[Ca(2+)](v) plateau following long trains in most varicosities. Hence, most varicosities possess alpha(2) adrenoceptors which are activated when noradrenaline accumulates extracellularly. 4. During long trains of impulses, the P(2y)-purinergic receptor agonist 2-methyl-thio-ATP (100 microM) decreased Delta[Ca(2+)](v) plateau by about 50% in most varicosities; alpha,beta-methylene ATP (100 microM) decreased it by about 50% in a minority of varicosities; adenosine (200 microM) had no significant effect. Suramin (100 microM) increased the Delta[Ca(2+)](v) during all stimulus protocols in most varicosities, suggesting that ambient ATP modulates Delta[Ca(2+)](v) responses. The P(2y) receptor antagonist reactive blue (100 microM) affected a minority of varicosities. Given that most varicosities respond to suramin, other P(2) receptor subtypes are probably present. 5. The ATP ectoenzyme antagonist ARL67157 (50 microM) decreased the plateau Delta[Ca(2+)](v) during long trains in complete strings of varicosities but not in others. 6. The present technique indicates that varicosities have diverse autoreceptor utilization.
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Affiliation(s)
- S C O'Connor
- Neurobiology Laboratory, Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
- Department of Physiology (F13), University of Sydney, NSW 2006, Australia
| | - K L Brain
- Neurobiology Laboratory, Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
- Department of Physiology (F13), University of Sydney, NSW 2006, Australia
| | - M R Bennett
- Neurobiology Laboratory, Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
- Department of Physiology (F13), University of Sydney, NSW 2006, Australia
- Author for correspondence:
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Abstract
The stem bark of Daniellia oliveri was screened phytochemically and a methanol extract prepared.-Condensed tannins, saponins, cyanogenetic and cardiac glycosides were identified in the crude drug. The cardiac glycoside components in the methanol extract were precipitated with acetone to yield a reddish-brown residue. The n-butanol soluble fraction of an aqueous solution of this residue tested positive for cardiac glycosides and was shown by TLC to contain steroidal compounds. This fraction was subjected to pharmacological studies on isolated rat bladder smooth muscle. It had no effect on purinergic neurotransmission but was a noncompetitive antagonist for muscarinic receptors.
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Affiliation(s)
- N D Onwukaeme
- Department of Pharmacognosy, Faculty of Pharmacy, University of Benin, PMB 1154, Benin City, Edo State, Nigeria
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Hardy TA, Brock JA. Effects of A1-adenosine receptor antagonists on purinergic transmission in the guinea-pig vas deferens in vitro. Br J Pharmacol 1999; 126:1761-8. [PMID: 10372818 PMCID: PMC1565967 DOI: 10.1038/sj.bjp.0702514] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/1998] [Revised: 01/27/1998] [Accepted: 02/03/1999] [Indexed: 11/08/2022] Open
Abstract
1. Intracellularly recorded excitatory junction potentials (ej.ps) were used to study the effects of adenosine receptor antagonists on neurotransmitter release from postganglionic sympathetic nerve terminals in the guinea-pig vas deferens in vitro. 2. The A1 adenosine receptor antagonists, 8-phenyltheophylline (10 microM) and 8-cyclopentyl-1,3-dipropylxanthine (0.1 microM), increased the amplitude of e.j.ps evoked during trains of 20 stimuli at 1 Hz in the presence, but not in the absence, of the alpha2-adrenoceptor antagonist, yohimbine (1 microM) or the non-selective alpha-adrenoceptor antagonist, phentolamine (1 microM). 3. Adenosine (100 microM) reduced the amplitude of e.j.ps, both in the presence and in the absence of phentolamine (1 microM). This inhibitory effect of adenosine is most likely caused by a reduction in transmitter release as there was no detectable change in spontaneous ej.p. amplitudes. 4. In the presence of phentolamine, application of the adenosine uptake inhibitor, S-(p-nitrobenzyl)-6-thioinosine (0.1 microM), had no effect on ej.p. amplitudes. 5. The phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (100 microM), significantly increased the amplitudes of all e.j.ps evoked during trains of 20 stimuli at 1 Hz, both in the presence and in the absence of phentolamine (1 microM). 6. These results suggest that endogenous adenosine modulates neurotransmitter release by an action at prejunctional A1 adenosine receptors only when alpha2-adrenoceptors are blocked.
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Affiliation(s)
- Todd A Hardy
- Prince of Wales Medical Research Institute, High Street, Randwick, NSW, 2031, Australia
| | - James A Brock
- Prince of Wales Medical Research Institute, High Street, Randwick, NSW, 2031, Australia
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Udoh FV. Effects of leaf and root extracts ofNauclea latifolia on purinergic neurotransmission in the rat bladder. Phytother Res 1995. [DOI: 10.1002/ptr.2650090402] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Driessen B, von Kügelgen I, Starke K. P1-purinoceptor-mediated modulation of neural noradrenaline and ATP release in guinea-pig vas deferens. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1994; 350:42-8. [PMID: 7935853 DOI: 10.1007/bf00180009] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The effect of P1-purinoceptor activation on contractions, release of noradrenaline and release of ATP elicited by electrical field stimulation (210 pulses, 7 Hz) was studied in the superfused vas deferens of the guinea pig. Release of noradrenaline was assessed as overflow of total tritium after preincubation with [3H]-noradrenaline. ATP was measured by means of the luciferin-luciferase technique. Electrical stimulation elicited reproducible contraction, tritium overflow and ATP overflow. In the absence of other drugs, adenosine (10-100 microM) did not change evoked contractions but reduced the evoked overflow of tritium and ATP. In subsequent experiments alpha 1-adrenoceptors were blocked by prazosin, P2-purinoceptors by suramin and alpha 2-adrenoceptors by rauwolscine. No or almost no contraction remained under these conditions. The evoked overflow of tritium was 505% and the evoked overflow of ATP 34% of that observed in the absence of prazosin, suramin and rauwolscine. Adenosine (1-100 microM) again reduced the evoked overflow of tritium and ATP, and so did the A1-selective agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 0.032-0.32 microM). Adenosine and CCPA decreased the evoked overflow of ATP to a greater extent than the evoked overflow of tritium. It is concluded that neural release of both postganglionic sympathetic cotransmitters, noradrenaline and ATP, is decreased upon activation of prejunctional P1- (A1-) purinoceptors in guinea-pig vas deferens. The A1-receptor-mediated inhibition of the release of ATP is more marked than the inhibition of the release of noradrenaline, a pattern opposite to the inhibition produced by activation of prejunctional alpha 2-autoreceptors.
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Affiliation(s)
- B Driessen
- Pharmakologisches Institut, Universität Freiburg, Germany
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Kurz K, von Kügelgen I, Starke K. Prejunctional modulation of noradrenaline release in mouse and rat vas deferens: contribution of P1- and P2-purinoceptors. Br J Pharmacol 1993; 110:1465-72. [PMID: 8306088 PMCID: PMC2175891 DOI: 10.1111/j.1476-5381.1993.tb13986.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
1. Prejunctional purinoceptors modulating the release of noradrenaline were compared in mouse and rat vas deferens. Tissue slices were preincubated with [3H]-noradrenaline and then superfused and stimulated electrically, in most experiments by trains of 60 pulses, 1 Hz. 2. In mouse vas deferens, 2-chloroadenosine (IC50 0.24 microM), beta,gamma-methylene-ATP (IC50 3.8 microM), alpha,beta-methylene-ATP (IC50 2.9 microM) and 2-methylthio-ATP (only 30 microM tested) reduced the evoked overflow of tritium. 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX), 10 nM, antagonized the effect of 2-chloro-adenosine (apparent pKB 10.2) as well as of beta,gamma-methylene-ATP (apparent pKB 9.6) and alpha,beta-methylene-ATP. Suramin, 300 microM, attenuated the effect of 2-chloroadenosine at best very slightly, antagonized the effect of beta,gamma-methylene-ATP (apparent pKB 4.5) and, when combined with DPCPX 10 nM, caused a further marked shift to the right of the concentration-response curve of beta,gamma-methylene-ATP beyond the shift produced by DPCPX alone. 3. In rat vas deferens, 2-chloroadenosine (IC50 0.20 microM), beta,gamma-methylene-ATP (IC50 4.8 microM), alpha,beta-methylene-ATP (IC50 3.0 microM) and 2-methylthio-ATP (only 30 microM tested) also reduced the evoked overflow of tritium. DPCPX, 10 nM, antagonized the effect of 2-chloroadenosine (apparent pKB 9.7) as well as of beta,gamma-methylene-ATP (apparent pKB 9.6) and alpha,beta-methylene-ATP. Suramin, 300 microM, did not change the effect of 2-chloroadenosine, attenuated the effect of beta,gamma-methylene-ATP at best very slightly and, when combined with DPCPX, caused at best a very small shift to the right of the concentration-response curve of beta,gamma-methylene-ATP beyond the shift produced by DPCPX alone.4. It is concluded that prejunctional purinoceptor mechanisms in mouse and rat vas deferens are similar. In either species, both nucleosides such as adenosine and nucleotides such as beta,gamma-methylene-ATP activate a common release-inhibiting receptor which is a Pl- or, more specifically, A1-purinoceptor.There seems to be no need to postulate the existence of a novel prejunctional P3-purinoceptor.Moreover, the sympathetic terminal axons possess an additional P2-purinoceptor in both species which is activated by some nucleotides such as beta,gamma-methylene-ATP and 2-methylthio-ATP, although the activation of the P2-purinoceptor by beta,gamma-methylene-ATP is difficult to demonstrate in the rat.
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Affiliation(s)
- K Kurz
- Pharmakologisches Institut, Freiburg, Germany
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Abstract
The effects of dopamine on non-adrenergic, non-cholinergic (NANC) neurotransmission have been investigated using rat bladder strips in-vitro. Dopamine administered alone did not produce any effect on the bladder but it depressed responses to NANC nerve stimulation in a dose-related fashion. All doses of dopamine employed depressed KCl-evoked contractions of the bladder to similar extents. The depressant action of dopamine on NANC transmission was not mediated by blockade of purinergic receptors, but was partially reversed by haloperidol. It is suggested that depression of NANC neurotransmission induced by dopamine in the rat bladder is partly mediated by dopaminergic receptors.
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Affiliation(s)
- T Y Lot
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmaceutical Sciences, University of Jos, Nigeria
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Bohmann C, Schollmeyer P, Rump LC. Methoxamine inhibits noradrenaline release through activation of alpha 1- and alpha 2-adrenoceptors in rat isolated kidney: involvement of purines and prostaglandins. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1993; 347:273-9. [PMID: 8097565 DOI: 10.1007/bf00167445] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effects of the alpha 1-adrenoceptor agonist methoxamine and the alpha 2-adrenoceptor agonist bromoxidine (UK 14034) on the stimulation induced (S-I) outflow of radioactivity at 100 Hz/6 pulses from rat isolated kidney preincubated with 3H-noradrenaline were investigated. Methoxamine (0.3-30 mumol/l) inhibited S-I outflow of radioactivity to a maximum of 83% with a pEC50 of 5.85 (5.71-5.94). UK 14304 (0.0003-0.3 mumol/l) inhibited S-I outflow of radioactivity to a maximum of 99% with a pEC50 of 8.35 (8.26-8.47). alpha-Adrenoceptor antagonist affinities (pKD) against methoxamine and UK 14304 at prejunctional alpha-adrenoceptors were determined. The concentration response curve of methoxamine was shifted to the right by the alpha 1/alpha 2B-adrenoceptor antagonist prazosin (0.1 mumol/l) with a pKD of 7.41 and that of UK 14304 by prazosin (0.3 mumol/l) with a pKD of 6.24. The alpha 2-adrenoceptor antagonist rauwolscine (0.1 mumol/l) shifted the concentration response curve of UK 14304 potently to the right with a pKD of 8.34. The concentration response curve of methoxamine was shifted also to the right by rauwolscine (0.1 mumol/l) and the alpha 2-adrenoceptor antagonist idazoxan (0.1 mumol/l), however, both antagonists suppressed the maximum response of methoxamine to 46% and 56%, respectively. A ten times lower concentration of rauwolscine (0.01 mumol/l) did not shift the concentration response curve of methoxamine but the inhibitory effect of methoxamine still reached only a maximum of 59%.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- C Bohmann
- Medizinische Universitätsklinik Freiburg, Innere Medizin IV, Federal Republic of Germany
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Mallard N, Marshall R, Sithers A, Spriggs B. Suramin: a selective inhibitor of purinergic neurotransmission in the rat isolated vas deferens. Eur J Pharmacol 1992; 220:1-10. [PMID: 1330614 DOI: 10.1016/0014-2999(92)90004-n] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effects of the putative P2 purinoceptor antagonist suramin on contractile responses of the rat isolated vas deferens to electrical field stimulation and exogenously applied drugs (alpha,beta-methylene ATP and noradrenaline) were investigated. Suramin was devoid of agonist activity in the rat vas deferens. The response of the vas deferens to single pulse field stimulation was characteristically biphasic with a large first component peaking between 260-300 ms after the stimulus followed by a second smaller component peaking at about 650 ms post-stimulus. Suramin (100 nM-1 mM) selectively impaired the first, purinergic phase of the response to single pulse field stimulation but was without effect on the second, noradrenergic component. The response of the vas deferens to trains of electrical field stimuli (10 Hz for 10 s) was also biphasic. Suramin (1 microM-1 mM) reduced the first (less than 1 s) phase of the response by 30%, the second (greater than 5 s) plateau phase by 50% and inhibited the intermediate (2-4 s) phase by 80%. Dose-contact periods of 20 or 30 min respectively were sufficient to achieve equilibration of the inhibitory effects of suramin against the responses to single pulse field stimulation or trains of pulses. Following 30 min incubation with 1 mM suramin, the remaining first and second phase components of the response to trains of pulses were impaired and subsequently abolished by the alpha 1-adrenoceptor antagonist WB4101 establishing their noradrenergic origin. Suramin (300 microM) abolished responses of the vas deferens to alpha,beta-methylene ATP but was without effect on those to noradrenaline. Suramin (30 microM) induced a rightward shift in the concentration-response relationship to alpha,beta-methylene ATP that was associated with a significant 40% increase in the maximum response, but did not modify responses to noradrenaline. The inhibitory effects of suramin (3-300 microM) on responses of the vas deferens to approximate EC50 concentrations of alpha,beta-methylene ATP were reversible on repeated washout for 40-60 min. These results reveal suramin to be a useful pharmacological tool for the study of purinergic neurotransmission in rodent vasa deferentia.
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Affiliation(s)
- N Mallard
- Department of Pharmacology and Therapeutics, University of Wales College of Medicine, Heath Park, Cardiff, South Glamorgan, UK
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Mallard NJ, Marshall RW, Spriggs TL. Neurotransmitter feedback is not important in modulating the noradrenergic component of responses of rat vas deferens to twin pulse electrical field stimulation. ACTA ACUST UNITED AC 1992; 12:165-74. [PMID: 1352779 DOI: 10.1111/j.1474-8673.1992.tb00374.x] [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: 11/29/2022]
Abstract
1. Drug effects on the full time-course of tension responses of the rat vas deferens to challenges of twin pulse field stimulation (TPFS) were examined. A microprocessor-controlled system was used to regulate stimulus delivery, on-line data collection and subsequent data analysis. 2. The second, noradrenergic phase of the response to the second stimulus of TPFS was missing when the interpulse interval was set at 3 s but was progressively restored as the interpulse interval was extended to 120 s. 3. With a 3 s interpulse interval, the missing second phase of the response to the second stimulus was not restored by the selective alpha 2-adrenoceptor antagonists yohimbine, imiloxan or idazoxan, indicative that alpha 2-adrenoceptor-mediated feedback inhibition of noradrenaline release is not the predominant mechanism modulating this response component. 4. Incubation with the P1-purinoceptor antagonist 8-phenyl-theophylline also failed to restore the missing noradrenergic component in the response to the second stimulus of TPFS. 5. Nevertheless, both responses to TPFS were impaired by the selective alpha 2-adrenoceptor agonist clonidine and by the P1-purinoceptor agonist 2-chloroadenosine, indicating the presence of functional presynaptic receptors of both types. These agonist-induced inhibitory effects were readily reversed by those antagonists which had failed to restore the missing noradrenergic component in the second response to TPFS.
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Affiliation(s)
- N J Mallard
- Department of Pharmacology and Therapeutics, University of Wales College of Medicine, Health Park, Cardiff, UK
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15
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von Kügelgen I, Starke K. Noradrenaline-ATP co-transmission in the sympathetic nervous system. Trends Pharmacol Sci 1991; 12:319-24. [PMID: 1658999 DOI: 10.1016/0165-6147(91)90587-i] [Citation(s) in RCA: 216] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Kaschube M, Brasch H. Pre- and postjunctional effects of N-ethylmaleimide in the isolated mouse vas deferens. Eur J Pharmacol 1990; 178:151-9. [PMID: 2328759 DOI: 10.1016/0014-2999(90)90470-q] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The influence of N-ethylmaleimide (NEM) on contractions due to exogenously applied noradrenaline and bethanechol and on the inhibitory effects of clonidine, of the enkephalin derivative, FK 33-824, and 2-chloroadenosine (2-CLA) on field stimulation-response curves and [3H]noradrenaline [( 3H]NA) release was studied in the isolated mouse vas deferens. Exposure to NEM (60 microM: 10 min) caused a 30% reduction of the maximal contraction due to NA but nearly abolished the response to bethanechol. NEM partially reversed the depression of the pulse width-response curves by clonidine and FK 33-824 but was without effect with 2-CLA. The contractions evoked by stimulation frequencies above 20 Hz were depressed by NEM both in presence and absence of the agonists. NEM diminished the inhibition of the stimulation-evoked release of [3H]NA by the three agonists. The prejunctional effect of NEM was markedly influenced by the stimulation parameters. These findings support the suggestion that the inhibition mediated by alpha 2-adrenoceptors, mu- and P1-receptors in the mouse vas deferens is NEM-sensitive and possibly transmitted by a pertussis toxin-sensitive G-protein.
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Affiliation(s)
- M Kaschube
- Department of Pharmacology, Medical University Lübeck, F.R.G
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von Kügelgen I, Schöffel E, Starke K. Inhibition by nucleotides acting at presynaptic P2-receptors of sympathetic neuro-effector transmission in the mouse isolated vas deferens. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1989; 340:522-32. [PMID: 2559333 DOI: 10.1007/bf00260607] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Effects of nucleotides and nucleosides on smooth muscle tension and the release of previously stored [3H]-noradrenaline were studied in the mouse isolated vas deferens. The tissue was stimulated twice by 20 electrical field pulses delivered at 2 Hz (S1, S2). alpha,beta-Methylene-ATP, ATP gamma S, ATP and UTP elicited contraction, with potency decreasing in that order; there was no contractile response to adenosine (up to 100 mumol/l) and uridine (up to 1 mmol/l). The electrically evoked overflow of tritium was reduced by the drugs in the following order of potency: ATP gamma S greater than ATP = adenosine greater than UTP; alpha,beta-methylene-ATP (up to 10 mumol/l) and uridine (up to 1 mmol/l) did not significantly change the evoked overflow. 8-(p-Sulphophenyl)theophylline did not alter the contractile responses to the nucleotides; it prevented the overflow-inhibiting effect of adenosine and reduced that of UTP; the overflow-inhibiting effects of ATP and ATP gamma S were not significantly attenuated. After prolonged exposure to alpha,beta-methylene-ATP, all contractile nucleotide effects were abolished; in contrast, the depression by adenosine and the nucleotides of the evoked overflow of tritium persisted. None of the effects was changed by indometacin, yohimbine or reactive blue 2. It is concluded that ATP, ATP gamma S, alpha,beta-methylene-ATP and UTP produce contraction of the vas deferens by activation of P2x-receptors. Moreover, the nucleotides inhibit per se the release of [3H]-noradrenaline (and presumably the co-transmitter mixture of noradrenaline and ATP); the effect of ATP is not, or only to a small extent, due to breakdown to adenosine. The presynaptic site of action of the purine nucleotides is a P2-receptor which differs from the P2x-receptor and may be a reactive blue 2-resistant "P2y-like" receptor.
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Affiliation(s)
- I von Kügelgen
- Pharmakologisches Institut, Freiburg, Federal Republic of Germany
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Charlton J, Hughes IE. Effect of meptazinol on evoked responses in rat vas deferens. J Pharm Pharmacol 1989; 41:762-5. [PMID: 2576044 DOI: 10.1111/j.2042-7158.1989.tb06361.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Responses of rat isolated vas deferens to electrical stimulation through field electrodes (400 mA, 1 ms duration, single shocks at 5 min intervals) were potentiated by meptazinol (10 to 300 microM) in whole tissues and also in the separated prostatic and epididymal portions. The effect was fast in onset, reproducible and easily reversed by washing. Prazosin (0.1 microM) practically abolished the response of the epididymal portion to electrical stimulation while the response of the prostatic portion was only slightly reduced (less than 20%). In the presence of prazosin, meptazinol still produced potentiation of the response of the prostatic portion. Nifedipine (2 microM) practically abolished the response of the prostatic portion to electrical stimulation while the response of the epididymal portion was only slightly reduced (less than 20%). In the presence of nifedipine, meptazinol no longer produced potentiation of the response of the epididymal portion. Exogenous ATP (5 microM to 1 mM) and phenylephrine (1 to 50 microM) produced a contractile response which was potentiated in the presence of meptazinol (100 microM) but in the presence of meptazinol (100 microM) and nifedipine (5 mM) together, potentiation of phenylephrine no longer occurred. It is suggested that potentiation by meptazinol of electrically induced responses in this tissue is due to a direct action on the smooth muscle.
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Affiliation(s)
- J Charlton
- Department of Pharmacology, University of Leeds, West Yorkshire, UK
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Gonçalves J, Carvalho F, Guimarães S. Uptake inhibitors do not change the effect of imidazoline alpha 2-adrenoceptor agonists on transmitter release evoked by single pulse stimulation in mouse vas deferens. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1989; 339:288-92. [PMID: 2566931 DOI: 10.1007/bf00173579] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The present study was undertaken to compare the presynaptic interaction of neuronal noradrenaline uptake inhibitors with imidazoline and phenylethylamine alpha 2-adrenoceptor agonists under two different conditions: at low and high noradrenaline concentrations in the biophase. Isolated mouse vasa deferentia were stimulated with trains of 7 pulses given at 0.2 Hz and the inhibition by the alpha 2-adrenoceptor agonists clonidine, alpha-methylnoradrenaline, and UK-14,304 of twitch responses was measured in the absence and in the presence of either cocaine (12 mumol/l) or desipramine (40 nmol/l). The effects were determined for the first (equivalent to single pulse stimulation) and the last stimulus of each train. Both uptake inhibitors antagonized the presynaptic inhibitory effects of imidazolines (clonidine and UK-14,304) on the last twitch; the effects on the first twitch remained unchanged. In contrast, the uptake inhibitors potentiated the inhibitory effect of the phenylethylamine (alpha-methylnoradrenaline) on both the first and the last twitches. These results support the view that the concentration of noradrenaline in the biophase plays a decisive role in the inhibition by alpha 2-adrenoceptor agonists of the electrically evoked release of noradrenaline. Agonists that are not substrates of neuronal uptake (i.e., clonidine, UK-14,304) become less effective when noradrenaline is present in the biophase while substrates of neuronal uptake (i.e., alpha-methylnoradrenaline) do not. The results argue against the hypothesis that uptake inhibitors interact directly with presynaptic alpha 2-adrenoceptors or act at some link between uptake and receptor sites.
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Affiliation(s)
- J Gonçalves
- Department of Pharmacology, Faculty of Pharmacy, University of Porto, Portugal
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