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Methylene ATP (methylene + atp)
Selected AbstractsRegional variation in electrically-evoked contractions of rabbit isolated pulmonary arteryBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2002V Margaret Jackson Electrically-evoked contractions in different regions of the rabbit isolated pulmonary artery have been investigated using stimulation parameters generally assumed to stimulate nerves selectively. In extrapulmonary artery, trains of stimuli (10 Hz; pulse width 0.1 ms) evoked monophasic contractions. In contrast, a biphasic contraction was evoked in the intrapulmonary artery consisting of an initial fast component followed by a secondary very long-lasting component. The contraction in the extrapulmonary artery was prazosin-sensitive (1 ,M) whereas that in the intrapulmonary artery was prazosin-resistant. ,,,-Methylene ATP (1 ,M), atropine (1 ,M), losartan (1 ,M), BIBO3304 (1 nM) or nifedipine (1 ,M) had no effect on the biphasic contraction of the intrapulmonary artery. Bretylium (2 ,M) abolished the contraction of extrapulmonary artery but only partially inhibited the initial component in the intra region with no effect on the second component. Tetrodotoxin (0.3,1 ,M), abolished the contraction of extrapulmonary artery but only partially reduced the electrically-evoked contraction of intrapulmonary artery. Removal of the endothelium and application of sulphisoxazole (0.6,22 ,M) had no effect. Varying the resting tone on the arteries, or applying gadolinium, had no effect on contractions. Using confocal microscopy and calcium imaging, reproducible whole cell calcium transients were evoked in individual smooth muscle cells in intact preparations but only when direct muscle stimulation was used (pulse width of 5,10 ms). No detectable changes in calcium were elicited when brief pulse widths were used (0.1,2 ms). Together, these data suggest that noradrenaline is the neurotransmitter inducing contraction in extrapulmonary artery. Noradrenaline and sympathetic nerves appear to play a less important role in the intrapulmonary artery. The tetrodoxin-resistant component is not mediated by ATP, NPY, acetylcholine, angiotensins, ET-1, stretch-activation or Ca2+ influx through L-type Ca2+ channels. Smooth muscle cells do not appear to be damaged by the stimulation protocol. The mechanism underlying the long lasting contraction of intrapulmonary artery evoked by brief electrical stimuli remains to be elucidated. British Journal of Pharmacology (2002) 137, 488,496. doi:10.1038/sj.bjp.0704863 [source] The P2Y1 receptor mediates ADP-induced p38 kinase-activating factor generation in human plateletsFEBS JOURNAL, Issue 8 2000Carol Dangelmaier U46619, a thromboxane A2 mimetic, but not ADP, caused activation of p38 mitogen activated protein (MAP) kinase in aspirin-treated platelets. In nonaspirinated human platelets ADP activated p38 MAP kinase in both a time-and concentration-dependent manner, suggesting that ADP-induced p38 MAP kinase activation requires generation of thromboxane A2. However, neither a thromboxane A2/prostaglandin H2 receptor antagonist SQ29548 and a thromboxane synthase inhibitor, furegrelate, either alone or together, nor indomethacin blocked ADP-induced p38 kinase activation in nonaspirinated platelets. Other cycloxygenase products, PGE2, PGD2, and PGF2,, failed to activate p38 kinase in aspirin-treated platelets. Hence, ADP must be generating an agonist, other than thromboxane A2, via an aspirin-sensitive pathway, which is capable of activating p38 kinase. AR-C66096, a P2TAC (platelet ADP receptor coupled to inhibition of adenylate cyclase) antagonist, did not inhibit ADP-induced p38 MAP kinase activation. The P2X receptor selective agonist, ,,,-methylene ATP, failed to activate p38 MAP kinase. On the other hand, the P2Y1 receptor selective antagonist, adenosine-2,-phosphate-5,-phosphate inhibited ADP-induced p38 kinase activation in a concentration-dependent manner, indicating that the P2Y1 receptor alone mediates ADP-induced generation of the p38 kinase-activating factor. These results demonstrate that ADP causes the generation of a factor in human platelets, which can activate p38 kinase, and that this response is mediated by the P2Y1 receptor. Neither the P2TAC receptor nor the P2X1 receptor has any significant role in this response. [source] Effect of human chorionic gonadotrophin on in vitro contractions of stimulated detrusor muscle strips of female ratsJOURNAL OF OBSTETRICS AND GYNAECOLOGY RESEARCH (ELECTRONIC), Issue 5 2009Diaa E. E. Rizk Abstract Aims:, We studied the effect of human chorionic gonadotrophin (hCG) on the in vitro detrusor muscle contractions in female rats. Methods:, Two adjacent detrusor muscle strips from the bladder dome of 18 female Wistar rats (230,250 gm) were mounted in an organ bath for the recording of isometric tension. Carbachol (10,9,10,3 M), ,,, methylene adenosine 5,-triphosphate (ATP) (10,9,10,3 M) and potassium chloride (KCl) (10,4,10,3 M) were applied (n = 6 × 3 groups). Concentration-response curves, before and after the addition of hCG (100 iu/mL) or oxybutynin (10,5 M) to either muscle strip, were compared. Results:, All curves were displaced to the right by hCG in a concentration-dependent manner with significant inhibition of contractions induced by carbachol (P < 0.001) and KCl (P = 0.016) but not those induced by ,,,-methylene ATP (P = 0.4). Estimated order of potency of inhibition was carbachol>KCl>,,,-methylene ATP. The overall inhibitory effect of hCG was significantly less than oxybutynin (P < 0.001). Conclusions:, hCG significantly inhibited in vitro detrusor contractions induced by depolarization (KCl) and cholinergic (carbachol) but not purinergic (,,,-methylene ATP) stimulation in a dose-dependent manner in female rats. [source] Excitatory purinergic neurotransmission in smooth muscle of guniea-pig taenia caeciTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Yong Zhang Non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmission has been an area of intense interest in gut motor physiology, whereas excitatory NANC neurotransmission has received less attention. In order to further explore excitatory NANC neurotransmission, we performed conventional intracellular recordings from guinea-pig taenia caeci smooth muscle. Tissue was perfused with oxygenated Krebs solution at 35°C and nerve responses evoked by either oral or aboral nerve stimulation (NS) (4 square wave pulses, 0.3 ms duration, 20 Hz). Electrical activity was characterized by slow waves upon which one to three action potentials were superimposed. Oral NS evoked an inhibitory junction potential (IJP) at either the valley or peak of the slow wave. Application of nifedipine (1 ,m) abolished slow waves and action potentials, but membrane potential flunctuations (1,3 mV) and IJPs remained unaffected. Concomitant application of apamin (300 nm), a small-conductance Ca2+ -activated K+ channel blocker, converted the IJP to an EJP that was followed by slow IJP. Further administration of NG -nitro- l -arginine methyl ester (l -NAME, 200 ,m), a nitric oxide synthase inhibitor, abolished the slow IJP without affecting the EJP, implying that the slow IJP is due to nitrergic innervation. The EJP was abolished by tetrodotoxin (1 ,m), but was not significantly affected by atropine (3 ,m) and guanethidine (3 ,m) or hexamethonium (500 ,m). Substance P (SP, 1 ,m) desensitization caused slight attenuation of the EJP, but the EJP was abolished by desensitization with ,,,-methylene ATP (50 ,m), a P2 purinoceptor agonist that is more potent than ATP at the P2X receptor subtype, suramin (100 ,m), a non-selective P2 purinoceptor antagonist, and pyridoxal-phosphate-6-azophenyl-2,,4,-disulphonic acid (PPADS, 100 ,m), a selective P2X purinoceptor antagonist. In contrast, the EJP was unaffected by MRS-2179 (2 ,m), a selective P2Y1 receptor antagonist. Aboral NS evoked an apamin- and l -NAME-sensitive IJP, but virtually no NANC EJP. These data suggest the presence of polarized excitatory purinergic neurotransmission in guinea-pig taenia caeci, which appears to be mediated by P2X purinoceptors, most likely the P2X1 subtype. [source] Electrophysiological classification of P2X7 receptors in rat cultured neocortical astrogliaBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2010W Nörenberg Background and purpose:, P2X7 receptors are ATP-gated cation channels mediating important functions in microglial cells, such as the release of cytokines and phagocytosis. Electrophysiological evidence that these receptors also occur in CNS astroglia is rare and rather incomplete. Experimental approach:, We used whole-cell patch-clamp recordings to search for P2X7 receptors in astroglial,neuronal co-cultures prepared from the cerebral cortex of rats. Key results:, All the astroglial cells investigated responded to ATP with membrane currents, reversing around 0 mV. These currents could be also detected in isolated outside-out patch vesicles. The results of the experiments with the P2X [,,,-methylene ATP and 2,-3,-O-(4-benzoyl) ATP] and P2Y receptor agonists [adenosine 5,-O-(2-thiodiphosphate), uridine 5,-diphosphate, uridine 5,-triphosphate (UTP) and UDP-glucose] suggested the involvement of P2X receptors in this response. The potentiation of ATP responses in a low divalent cation or alkaline bath, but not by ivermectin, made it likely that a P2X7 receptor is operational. Blockade of the ATP effect by the P2X7 antagonists Brilliant Blue G, calmidazolium and oxidized ATP corroborated this assumption. Conclusions and implications:, Rat cultured cortical astroglia possesses functional P2X7 receptors. It is suggested that astrocytic P2X7 receptors respond to high local ATP concentrations during neuronal injury. [source] Cannabinoids inhibit noradrenergic and purinergic sympathetic cotransmission in the rat isolated mesenteric arterial bedBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2007P Pakdeechote Background and purpose: Noradrenaline and ATP are sympathetic co-transmitters. In the rat perfused mesenteric bed cannabinoids have been shown to modify the overall response to sympathetic nerve stimulation. This study has assessed whether cannabinoid receptor activation modulates differentially the noradrenergic and purinergic components of sympathetic vasoconstriction. Experimental approach: Rat mesenteric beds were perfused with physiological salt solution and the effects of cannabinoids on responses to nerve stimulation, or exogenous noradrenaline or ,,, -methylene ATP (,,, -meATP; P2X receptor agonist) were determined after raising tone with U46619. The effects of cannabinoids on the noradrenaline and ATP components of sympathetic neurotransmission were assessed using the ,1 -adrenoceptor antagonist, prazosin, or after P2X receptor desensitization with ,,, -meATP. Key results: Anandamide, WIN 55,212-2 and CP55,940 attenuated sympathetic neurogenic vasoconstrictor responses. The inhibitory actions of anandamide and WIN 55,212-2 were blocked by LY320135, a CB1 receptor antagonist, but not by SR144528, a CB2 receptor antagonist. The inhibitory actions of CP55,940 were unaffected by LY320135 and SR144528. WIN 55,212-3, the inactive S(,) enantiomer of WIN 55,212-2, had no effect on sympathetic neurogenic responses. None of the cannabinoids affected contractile responses to exogenous noradrenaline or ,,, -meATP. Anandamide and WIN 55,212-2 inhibited both the noradrenaline and ATP components of the sympathetic neurogenic contractile responses, with effects on the ATP component being most marked. Conclusions and implications: These results indicate that prejunctional CB1 -like receptors mediate the sympathoinhibitory action of anandamide and WIN 55,212-2, but not CP55,940, in the rat mesenteric bed. Cannabinoids inhibit both the noradrenergic and purinergic components of sympathetic neurotransmission. British Journal of Pharmacology (2007) 152, 725,733; doi:10.1038/sj.bjp.0707397; published online 16 July 2007 [source] Expression of Rho-kinase and its functional role in the contractile activity of the mouse vas deferensBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2003Kansu Büyükaf The effects of two Rho-kinase inhibitors, Y-27632 and fasudil, were investigated on the contractions produced by electrical field stimulation (EFS, 40 V, 1 mS, 2, 4, 8 and 16 Hz, for 20 s), KCl (30 , 60 mM), phenylephrine (Phe) (10,5 , 10,4M), adenosine-3,, 5,-triphosphate (ATP) (10,4 , 10,3M) and ,,, -methylene ATP (10,5M). EFS produced frequency-dependent reproducible contractile activity, which was almost abolished by guanethidine (10,5M, for 1 h). This contraction consisted of two components (a phasic initial contraction followed by a tonic one), and it was inhibited by Y-27632 and fasudil (both at 10,5M). However, these inhibitors had no effect on resting tension of the tissue. Contractions elicited by KCl (30 , 60 mM) were insensitive to guanethidine (10,5M, for 1 h), but suppressed by Y-27632 (10,5M) and fasudil (10,5M). In addition, the contractions induced by Phe (an ,1 -adrenoceptor agonist) and ATP (a purinergic agent) were inhibited significantly by Y-27632 (10,5M). Phasic contractions evoked by the selective P2X purinoceptor agonist ,,, -methylene ATP were also suppressed by Y-27632 (10,5M). Western blot analysis revealed that the mouse vas deferens expresses Rho-kinase (ROK,, ROCK-2 isoform) protein with a molecular weight of approximately 160 kDa. As a positive control, the presence of this protein was also shown in homogenates of smooth muscle from the rat mesenteric artery. In conclusion, Rho-kinase protein is expressed in the mouse vas deferens, and it mediates neurogenic contractile activity as well as the contractions induced by KCl, Phe, ATP and ,,, -methylene ATP. Owing to the suppressive effects of Rho-kinase inhibitors on the contractile activity of the vas deferens, the possibility that these compounds might impair ejaculation must be taken into account when considering them as potential agents in the treatment of erectile dysfunction. British Journal of Pharmacology (2003) 140, 743,749. doi:10.1038/sj.bjp.0705479 [source] Mechanism of prolonged vasorelaxation to ATP in the rat isolated mesenteric arterial bedBRITISH JOURNAL OF PHARMACOLOGY, Issue 3 2001Vera Ralevic This study investigated the mechanism of prolonged relaxation to ATP in the rat isolated perfused mesenteric arterial bed. In methoxamine pre-constricted preparations, ATP elicited dose-dependent, endothelium-dependent, rapid relaxation at 5 pmol , 0.05 ,mol (Rmax 76±5.6%, pD2 9.2±0.2), and contraction, followed by prolonged endothelium-independent vasorelaxation at 0.05, 0.5 and 5 ,mol (56±3.0, 87±2.9 and 85±4.6%). Suramin (100 ,M), attenuated rapid (pD2 7.8±0.1) and prolonged relaxation to ATP. The selective P2 receptor antagonist PPADS (10 ,M) reduced prolonged, but not rapid relaxation. Neither phase of relaxation was affected by 8-sulphophenyltheophylline (1 ,M) or indomethacin (10 ,M). ,,,-methylene ATP (,,,-meATP; 10 ,M) attenuated prolonged relaxation to ATP (relaxations at 0.05 and 0.5 ,mol were 25±8.3 and 48±9.0%, respectively). ,,,-meATP blocked contractions and revealed rapid relaxation to ATP at 0.05 , 5 ,mol. Capsaicin pre-treatment did not affect either phase of vasorelaxation to ATP. ,,,-meATP (10 ,M) had no effect on vasorelaxation mediated by electrical stimulation of capsaicin-sensitive sensory nerves. High K+ (25 mM) attenuated prolonged relaxation to ATP (21±2.6 and 64±5.8%, at 0.05 and 0.5 ,mol, respectively), but had no effect on rapid relaxation. Ouabain (1 mM), an inhibitor of Na+/K+ -ATPase, and glibenclamide (10 ,M), an inhibitor of KATP channels, also attenuated prolonged relaxation to ATP. Charybdotoxin (100 nM), a selective inhibitor of KCa channels, and tetraethylammonium (10 mM) had no effect on rapid or prolonged relaxations. These results show that the prolonged phase of vasorelaxation to ATP in the rat isolated mesenteric arterial bed, which may be mediated by P2Y receptors, is endothelium-independent, involves activation of Na+/K+ -ATPase and KATP channels, and is inhibited by ,,,-meATP. Neither prolonged nor rapid vasorelaxation to ATP involves capsaicin-sensitive sensory nerves, adenosine P1 receptors, prostanoids or KCa channels. British Journal of Pharmacology (2001) 132, 685,692; doi:10.1038/sj.bjp.0703868 [source] Multiple P2X receptors on guinea-pig pelvic ganglion neurons exhibit novel pharmacological propertiesBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2001Yu Zhong Application of ATP and ,,,-methylene ATP (,,meATP) to voltage-clamped guinea-pig pelvic neurons produced three types of inward currents. A fast-desensitizing response was present in 5% (25/660) of neurons, 70% gave slowly-desensitizing currents, and the remainder had biphasic responses. Slowly-desensitizing responses were characterized pharmacologically. The response to ,,meATP 100 ,M was 46±27% (range 0 , 100%) of that evoked by ATP 100 ,M in the same cell. Cross-desensitization indicated the presence of ,,meATP-sensitive and -insensitive receptors. The concentration-response curve for ,,meATP had an EC50 of 55 ,M, and a Hill coefficient of 0.99, while at the ,,meATP-insensitive receptor, ATP had an EC50 of 73 ,M, with a Hill coefficient of 1.78. The response to ,,meATP was blocked by pyridoxalphosphate-6-azophenyl-2,,4,-disulphonic acid (PPADS), suramin and Cibacron blue. However, the ,,meATP-insensitive receptor was inhibited by PPADS, but not by the other two antagonists. 2,- (or 3,-) O -trinitrophenyl-ATP was 10 times more potent in inhibiting responses to ,,meATP than to ATP (at the ,,meATP-insensitive receptor). Lowering extracellular pH potentiated responses to ,,meATP and ATP, while raising pH attenuated them. Co-application of Zn2+ (3 , 300 ,M) inhibited the responses to ,,meATP and ATP, with IC50 values of 286 and 60 ,M, respectively. In conclusion, unlike rat and mouse pelvic ganglion neurons, which only express P2X2 homomers, at least three distinct P2X receptors are present in guinea-pig pelvic neurons, probably homomeric P2X2, P2X3 and heteromeric P2X2/3 receptors. However, some of the novel pharmacological properties observed suggest that the guinea-pig P2X receptor subtypes may differ from their rat orthologues. British Journal of Pharmacology (2001) 132, 221,233; doi:10.1038/sj.bjp.0703778 [source] EXPRESSION OF P2X PURINOCEPTORS IN PC12 PHAEOCHROMOCYTOMA CELLSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 12 2007Ji-Hu Sun SUMMARY 1The PC12 cell line, which was cloned from a rat adrenal phaeochromocytoma, is a useful model system. It expresses neuronal properties after treatment with nerve growth factor (NGF). The nervous system-specific P2X receptor subtype P2X2 was initially cloned from PC12 cells, but little is known about the expression of other subtypes of P2X receptors in PC12 cells. The aim of the present study was to investigate whether PC12 cells express the other P2X receptors when exposed to NGF. 2Reverse transcription,polymerase chain reaction at the mRNA level and immunocytochemisty at the protein level showed that, among the seven P2X purinoceptor subtypes, only P2X2 was found to be expressed in undifferentiated PC12 phaeochromocytoma cells, but all seven P2X purinoceptor subtypes were expressed in differentiated PC12 cells treated with 50 µg/mL NGF. 3Electrophysiological recordings indicated that ATP (30 µmol/L) but not ,,,-methylene ATP (,,,-meATP; 30 µmol/L) evoked an inward current in undifferentiated PC12 cells, but both ,,,-meATP and ATP evoked inward currents in differentiated PC12 cells. The results indicate that the NGF-induced P2X receptors expressed in PC12 cells are functional channels. 4The present study suggests that the NGF-induced neuronal phenotype of PC12 cells may be a model for the study of P2X heteromeric receptors. [source] DYSFUNCTION OF PURINERGIC REGULATION OF SYMPATHETIC NEUROTRANSMISSION IN SHR/NDMCR-CP (SHR-CP) RATCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 2004Naoko Tanaka SUMMARY 1.,The effect of 2-chloroadenosine (2CA), a P1 receptor agonist and ,,,-methylene ATP (,,mATP), a P2 receptor agonist, on the overflow of endogenous noradrenaline (NE) and the contractile response were examined in the electrically field-stimulated (EFS) (1 Hz) caudal artery obtained from Wistar-Kyoto (WKY) and SHR/NDmcr-cp (SHR-cp) rats. 2.,Both 2CA and ,,mATP reduced the EFS-evoked release of NE from the arteries of WKY. Also, 2CA significantly reduced the EFS-evoked contractile response in WKY, while it had no effect at all in SHR-cp. ,,mATP significantly reduced the EFS-evoked contractile response in both WKY and SHR-cp. Both 2CA and ,,mATP did not affect the contractile response induced by NE at 1 µmol/L. 3.,These results indicate that in the caudal arteries of SHR-cp, the P2 agonist but not the P1 agonist is functional in the prejunctional inhibitory regulation of adrenergic neurotransmission. This P1 dysfunction may play a role in the sympathetic hyperinnervation in metabolic syndrome. [source] | ||||||||||