Search results for " Purinergic"
showing 10 items of 42 documents
Interference with purinergic signalling
2016
Objective: The association of abacavir (ABC), a guanosine analogue, with cardiovascular toxicity is a long-lasting matter of controversy engendered by the lack of a mechanism of action. Clinical data point to an acute mechanism of vascular inflammation. Previous studies have shown that ABC induces leukocyte-endothelial cell interactions, an indicator of vascular inflammation. These effects are reproduced by another purine analogue, didanosine, but not by pyrimidine or acyclic nucleotide analogues, hinting at an interference with the purinergic system. The aim of the present study was to assess the role of ATP-receptors in leukocyte accumulation induced by ABC. Design and methods: Clinical c…
Inhibitory responses to exogenous adenosine in murine proximal and distal colon”
2006
The aims of the present study were firstly, to characterize pharmacologically the subtypes of P(1) purinoreceptors involved in the inhibitory effects induced by exogenous adenosine in longitudinal smooth muscle of mouse colon, and secondly, to examine differences in the function and distribution of these receptors between proximal and distal colon. Adenosine (100 microM-3 mM) caused a concentration-dependent reduction of the amplitude of spontaneous contractions in the proximal colon, and muscular relaxation in the distal colon. In the proximal colon, adenosine effects were antagonized by a selective A(1) receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 10 nM), but were not m…
Negative regulation of diacylglycerol kinase θ mediates adenosine-dependent hepatocyte preconditioning
2010
In liver ischemic preconditioning (IP), stimulation of adenosine A2a receptors (A2aR) prevents ischemia/reperfusion injury by promoting diacylglycerol-mediated activation of protein kinase C (PKC). By concerting diacylglycerol to phosphatidic acid, diacylglycerol kinases (DGKs) act as terminator of diacylglycerol signalling. This study investigates the role of DGK in the development of hepatocyte IP. DGK activity and cell viability were evaluated in isolated rat hepatocytes preconditioned by 10 min hypoxia followed by 10 min re-oxygenation or by the treatment with the A2aR agonist, CGS21680, and subsequently exposed to prolonged hypoxia. We observed that after IP or A2aR activation, a decre…
Alterations in striatal neuropeptide mRNA produced by repeated administration of L-DOPA, ropinirole or bromocriptine correlate with dyskinesia induct…
2002
Chronic administration of L-DOPA to MPTP-treated common marmosets induces marked dyskinesia while repeated administration of equivalent antiparkisonian doses of ropinirole and bromocriptine produces only mild involuntary movements. The occurrence of dyskinesia has been associated with an altered balance between the direct and indirect striatal output pathways. Using in situ hybridisation histochemistry, we now compare the effects of these drug treatments on striatal preproenkephalin-A (PPE-A) and adenosine A(2a) receptor mRNA expression as markers of the indirect pathway and striatal preprotachykinin (PPT) mRNA and preproenkephalin-B (PPE-B, prodynorphin) mRNA expression as markers of the d…
Functional role of cholinoceptors and purinoceptors in human isolated atrial and ventricular heart muscle
1989
1. The effects of cholinergic and purinergic stimulation on action potential, force of contraction and 86Rb efflux were investigated in human atrial and ventricular heart muscle. 2. In atrial heart muscle, carbachol and (-)-N6-(R-phenyl-isopropyl)-adenosine (R-PIA) and 5'-(N-ethyl)-carboxamido-adenosine (NECA) evoked transient decreases of action potential duration and force of contraction; the steady-state effects on force of contraction were virtually identical to control values. In the presence of propranolol, steady-state values after carbachol, R-PIA or NECA amounted to about 50% of control values. 3. In ventricular heart muscle, carbachol, NECA and R-PIA did not significantly affect t…
Nitrergic and purinergic interplay in inhibitory transmission in rat gastric fundus.
2007
Summary 1 This study was undertaken to analyse the involvement of ATP in non-adrenergic non- cholinergic (NANC) relaxation and possible interplay between nitrergic and purinergic systems in rat gastric fundus. 2 Experiments were performed in vitro on strips of longitudinal muscle from rat gastric fundus, recording the mechanical activity as changes in isometric force. In addition, NO release induced by different experimental conditions was assayed. 3 Under NANC conditions in serotonin-precontracted strips, electrical field stimulation (EFS) elicited a tetrodotoxin (TTX)-sensitive relaxation accompanied by nitric oxide (NO) release. This effect was antagonized by pretreatment with the NO …
Inhibitory purinergic transmission in mouse caecum: Role for P2Y1 receptors as prejunctional modulators of ATP release
2007
Using conventional microelectrode recording techniques, we investigated, in the circular muscle of the mouse caecum, the neurotransmitter(s) involved in the neurally-evoked inhibitory junction potentials (IJPs) and the existence of possible prejunctional mechanisms controlling neurotransmitter release. Electrical field stimulation with single pulses elicited IJPs, consisting only of a "fast" hyperpolarization, while using train stimuli (30-50 Hz) the initial fast hyperpolarization was followed by a slower hyperpolarization. The fast and the slow component were selectively antagonized by apamin, a blocker of calcium-activated potassium channels, and N(omega)-nitro-l-arginine methyl ester (l-…
Mechanisms underlying hyperpolarization evoked by P2Y receptor activation in mouse distal colon
2006
In murine colonic circular muscle, ATP mediates fast component of the nerve-evoked inhibitory junction potentials, via activation of P2Y receptors and opening of apamin-sensitive Ca2+-dependent K+ channels. We investigated, using microelectrode recordings, the intracellular events following P2Y-receptor activation by electrical field stimulation or by adenosine 5'-O-2-thiodiphosphate (ADPbetaS), ATP stable analogue. The fast-inhibitory junction potential amplitude was reduced by thapsigargin or ciclopiazonic acid (CPA), sarcoplasmic reticulum Ca2+-ATPase inhibitors, by ryanodine, which inhibits Ca2+ release from ryanodine-sensitive stores, and by 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (S…
Activation of P2Y receptors by ATP and by its analogue, ADPbetaS, triggers two calcium signal pathways in the longitudinal muscle of mouse distal col…
2008
Our previous research showed that ATP and adenosine 5'-O-2-thiodiphosphate (ADPbetaS) induce contractile effects in the longitudinal muscle of mouse distal colon via activation of P2Y receptors which are not P2Y(1) or P2Y(12) subtypes. This study investigated the nature of the P2Y receptor subtype(s) and the mechanisms leading to the intracellular calcium concentration increase necessary to trigger muscular contraction. Motor responses of mouse colonic longitudinal muscle to P2Y receptor agonists were examined in vitro as changes in isometric tension. ATP or ADPbetaS induced muscular contraction, which was not affected by P2Y(11) or P2Y(13) selective antagonists. Calcium-free solution or th…
Involvement of the P2X7 purinergic receptor in colonic motor dysfunction associated with bowel inflammation in rats
2014
Background and Purpose Recent evidence indicates an involvement of P2X7 purinergic receptor (P2X7R) in the fine tuning of immune functions, as well as in driving enteric neuron apoptosis under intestinal inflammation. However, the participation of this receptor in the regulation of enteric neuromuscular functions remains undetermined. This study was aimed at investigating the role of P2X7Rs in the control of colonic motility in experimental colitis. Experimental Approach Colitis was induced in rats by 2,4-dinitrobenzenesulfonic acid. P2X7R distribution was examined by immunofluorescence analysis. The effects of A804598 (selective P2X7R antagonist) and BzATP (P2X7R agonist) were tested on co…