cgs-24012 and 3-7-dimethyl-1-propargylxanthine

In the kidney, adenosine (ADO) can induce either vasoconstriction or vasodilatation, mediated by A1 or A2 receptors, respectively. The vasodilator influence may be of special importance in the renal medulla which operates at low tissue pO(2) levels and is susceptible to ischaemic damage. It has not been established if ADO induced vasodilatation is modified by salt intake.. We examined effects of stimulation or inhibition of ADO receptors (A2R) on perfusion of the renal cortex and medulla on low- or high- sodium intake (LS, HS). Effects of suprarenal aortic ADO (0.03 mmol/kg/h), A2R agonist (DPMA), 0.08-0.4 mmol/kg/h, or antagonist (DMPX), 1.7 micromol/kg/h, were examined in anaesthetized rats maintained on LS (0.15% Na) or HS (4% Na) diet for 3 weeks. Whole kidney blood flow (RBF) and the perfusion (laser-Doppler) of the superficial cortex and outer and inner medulla (OM-BF, IM-BF) were measured.. In LS rats neither drug changed renal perfusion. In HS rats ADO increased RBF 18 +/- 3%, OM-BF 16 +/- 7% and IM-BF 16 +/- 6%. IM-BF increased after DPMA 18 +/- 5% and decreased after DMPX 13 +/- 3%; neither drug consistently changed perfusion of the cortex.. On HS intake, medullary perfusion is controlled by ADO vasodilator (A2) receptors, which may help provide adequate oxygen to the medulla, the zone which normally operates under relative hypoxia. On LS intake, the vasodilator and vasoconstrictor effects are probably in balance and ADO has little role in control of intrarenal circulation.

Topics: Adenosine; Animals; Humans; Kidney; Kidney Cortex; Laser-Doppler Flowmetry; Male; Oxygen; Perfusion; Rats; Rats, Wistar; Receptors, Adenosine A2; Salts; Sodium; Theobromine; Treatment Outcome

1. The modulation of voltage-dependent Ca2+ currents (ICa) by adenosine was investigated in magnocellular neurones acutely dissociated from the rat hypothalamic supraoptic nucleus (SON) by using the whole-cell patch-clamp technique. 2. Adenosine dose dependently and reversibly inhibited ICa elicited by depolarizing voltage steps from a holding potential of -80 mV to potentials ranging from -30 to +20 mV. The mean (+/- s.e.m.) maximum inhibition rate was 36.1 +/- 4.1 % (n = 6) at -20 mV and the EC50 was 9.8 x 10-7 M (n = 6). 3. The inhibition of ICa by adenosine was completely reversed by the selective A1 receptor antagonist 8-cyclopentyl theophylline (CPT), and was mimicked by the selective A1 receptor agonist N 6-cyclohexyladenosine (CHA). 4. The inhibition by CHA was strongly reduced when ICa was inhibited by omega-conotoxin GVIA, a blocker of N-type Ca2+ channels. 5. The adenosine-induced inhibition of ICa was largely reversed by a depolarizing prepulse to +150 mV for 100 ms, which is known to reverse the inhibition of Ca2+ channels mediated by G-protein betagamma subunits. 6. The adenosine receptor-mediated inhibition of ICa was not abolished by intracellularly applied preactivated pertussis toxin (PTX). 7. Using immunohistochemistry, Gzalpha-like immunoreactivity (a PTX-resistant inhibitory G-protein) was observed throughout the SON. 8. These results suggest that adenosine modulates the neuronal activity of SON neurones by inhibiting N-type voltage-dependent Ca2+ channels via A1 receptors which are coupled to PTX-resistant G-proteins.

Topics: Adenosine; Animals; Calcium Channels; Calcium Channels, N-Type; In Vitro Techniques; Male; Neurons; Patch-Clamp Techniques; Rats; Rats, Wistar; Receptor, Adenosine A2A; Receptor, Adenosine A2B; Receptor, Adenosine A3; Receptors, Purinergic P1; Reverse Transcriptase Polymerase Chain Reaction; Supraoptic Nucleus; Tetrodotoxin; Theobromine

Effects of adenosine and pGlu-Glu-ProNH(2) (FPP) on the function and in vitro penetration of boar spermatozoa were examined. First, the effects of dibutyryl cAMP or agonists and antagonists of adenosine receptors (inhibitory adenosine receptors, A1AdR; stimulatory adenosine receptors, A2AdR) on freshly ejaculated spermatozoa were determined by chlortetracycline fluorescence assessment. Capacitation of spermatozoa was stimulated when they were cultured in a medium with dibutyryl cAMP, adenosine, A2AdR agonist, and adenosine plus A1AdR antagonist (CPT). However, acrosome reaction was inhibited only by adenosine. A1AdR agonist did not affect intact spermatozoa. A2AdR antagonist (DMPX) neutralized all of the effects of adenosine. Second, interaction of adenosine and FPP was examined. Gln-FPP, a competitive inhibitor of FPP, and DMPX inhibited the effects of adenosine and FPP, and CPT neutralized the inhibitory effect of FPP on acrosome reaction. Last, the effects of adenosine, FPP, and caffeine on the rate of sperm penetration were examined using frozen-thawed spermatozoa. Adenosine, FPP, and caffeine significantly enhanced the rate of sperm penetration as compared with the case of no additions. Caffeine treatment resulted in a high rate of polyspermic fertilization. In contrast, adenosine and FPP treatments resulted in an increased proportion of normal fertilization in in vitro-matured oocytes. These results suggest that boar spermatozoa can be modulated by the adenylyl cyclase/cAMP pathway via A2AdR in intact cells to induce capacitation and A1AdR in capacitated cells to inhibit spontaneous acrosome loss and that FPP receptors interact with A2AdR in intact cells and with A1AdR in capacitated cells. Furthermore, adenosine and FPP seem to be useful in reducing the incidence of polyspermic penetration.

Topics: Adenosine; Animals; Bucladesine; Cryopreservation; Female; Male; Purinergic P1 Receptor Antagonists; Pyrrolidonecarboxylic Acid; Receptors, Cytoplasmic and Nuclear; Receptors, Purinergic P1; Semen Preservation; Sperm-Ovum Interactions; Spermatozoa; Swine; Theobromine; Thyrotropin-Releasing Hormone

To clarify the effects of adenosine receptor subtypes (A1, A2 and A3) on hippocampal serotonin (5-HT) release and 5-HT reuptake activity, hippocampal extracellular 5-HT levels were determined in vivo by microdialysis in freely moving rats. Selective 5-HT reuptake inhibitor (SSRI) fluoxetine and DU24565 increased extracellular 5-HT levels. Adenosine and A1 receptor agonist, 2-chloro-N6-cyclopentyl-adenosine (CCPA), decreased extracellular 5-HT levels, whereas non-selective antagonist, caffeine, and A1 antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT) increased them. When 5-HT reuptake activity was inhibited by DU24565 and fluoxetine, the effects of CPT and CCPA on 5-HT level were enhanced. A2A receptor agonist, CGS21680, A2 receptor agonist, PD125944, A2 receptor antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX), and A3 receptor agonist, N6-2-(4-aminophenyl)ethyladenosine (APNEA) did not affect 5-HT levels; however, when A1 receptor was blocked by CPT, 5-HT levels were increased by adenosine, CGS21680 and PD125944, and decreased by DMPX and APNEA. Under conditions of A1 receptor blockade, pretreatment with DU24565 or fluoxetine, enhanced the stimulatory effects of CGS21680 and PD125944 as well as inhibitory effects of DMPX on 5-HT level, whereas the inhibitory effect of APNEA was abolished. These results indicate that the stimulatory effects of A2 receptor and inhibitory effects of A3 receptor on hippocampal extracellular 5-HT levels are masked or abolished by the inhibitory effects of A1 receptor. In addition, hippocampal serotonergic transmission might be modulated by hippocampal presynaptic adenosine receptor subtypes, and hippocampal 5-HT reuptake activity might be modulated by hippocampal A3 receptor.

Topics: Adenosine; Animals; Antihypertensive Agents; Biological Transport; Caffeine; Central Nervous System Stimulants; Fluoxetine; Hippocampus; Male; Microdialysis; Phenethylamines; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Quipazine; Rats; Rats, Wistar; Receptor, Adenosine A2A; Receptor, Adenosine A3; Receptors, Purinergic P1; Selective Serotonin Reuptake Inhibitors; Serotonin; Serotonin Antagonists; Theobromine; Theophylline; Vasodilator Agents

It is well-known that nucleotides, nucleosides and purine/pyrimidine bases enhance cell proliferation in vitro. Nevertheless, the molecular mechanisms involved in this mitogenic activity is still controversial, since these compounds are reported both to synergize with growth factor, and to act directly on purinergic receptor inducing per se a proliferative response. It was suggested that cell growth enhancement could be mediated by the A2 purinergic receptor activation. Here we report that a polydeoxyribonucleotide (PDRN) and adenosine are able to increase, the growth rate of human skin fibroblasts in primary cultures. The proliferative activity exerted by PDRN was significantly counteracted by the A2 antagonist 3, 7-Dimethyl-1-propargylxanthine (DMPX), but not by the A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (PD 116,948, DPCPX). Accordingly, the trophic action of PDRN was mimicked by the A2 agonist N6-[2-(3,5-Dimethoxyphenyl)-2-(methylphenyl)-ethyl]adenosine (DPMA), while the A1 agonist N6-Cyclopenthyladenosine (CPA) did not show any effect. In microfluorimetric studies, we observed that PDRN and adenosine increased the concentration of cytosolic calcium ions. The PDRN-evoked calcium rise was dose-dependent and DMPX sensitive. Taken together, our results suggest that PDRN may operate as a pro-drug providing the cultured cells with an effective amount of mitogenic deoxyribonucleotides, deoxyribonucleosides and bases; moreover, cell proliferation enhancement that has been induced by PDRN seems to be mediated, at least in part, by the activation of purinergic receptors of the A2 subtype.

Topics: Adenosine; Calcium; Cell Division; Cytophotometry; Deoxyribonucleosides; Deoxyribonucleotides; Fibroblasts; Fura-2; Humans; Oligodeoxyribonucleotides; Placenta; Receptors, Purinergic P1; Second Messenger Systems; Theobromine; Xanthines

To determine the modulatory action of adenosine-receptor stimulation on [Ca2+]i responses to beta-adrenoceptor stimulation in the heart of the spontaneously hypertensive rat (SHR), the electrically induced [Ca2+]i transient in response to isoproterenol (ISO) in single ventricular myocytes pretreated with adenosine agonists in SHRs and its normotensive control Wistar-Kyoto (WKY) rats was measured with a spectrofluorometric method by using fura-2/AM as the calcium indicator. In both types of rat, ISO at 0.001-1 microM augmented the electrically induced [Ca2+]i transient, and the effect was blocked by a beta-adrenoceptor blocker, propranolol. In SHRs that did not exhibit cardiac hypertrophy, the resting level of [Ca2+]i and the amplitude of the electrically induced [Ca2+]i transient were the same as those in WKY rats, whereas the augmentation of the electrically induced [Ca2+]i transient in response to ISO was significantly lower than that in WKY rats. In WKY rats, the effects of ISO on the electrically induced [Ca2+]i transient were inhibited by the adenosine A1-receptor agonist, R(-)-N6-(2-phenylisopropyl)adenosine (R-PIA) at 0.01-10 microM. In contrast, the effects of ISO were further enhanced by the adenosine A2-receptor agonist, N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)-ethyl)]adenosine (DPMA) at 1-10 microM. In SHRs, the inhibitory effect of R-PIA was significantly reduced, whereas the excitatory effect of DPMA was absent. The effects of both adenosine-receptor agonists in both types of rat were abolished by the respective adenosine-receptor antagonists, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and 3,7-dimethyl-1-propargylxanthine (DMPX). The results indicate that the modulatory actions of adenosine-receptor stimulation on [Ca2+]i response to beta-adrenoceptor stimulation in the hearts of SHRs are reduced, which is independent of cardiac hypertrophy.

Topics: Adenosine; Adrenergic beta-Agonists; Animals; Calcium; Cardiotonic Agents; Electric Stimulation; Heart Ventricles; Isoproterenol; Male; Myocardium; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Theobromine; Vasodilator Agents; Xanthines

The effects of magnesium ion (Mg2+), adenosine A1 and A2 receptor ligands on basal extracellular levels of striatal dopamine, hippocampal dopamine and serotonin were investigated by using in vivo microdialysis in freely moving rats. An increase in extracellular levels of Mg2+ ([Mg2+]o) reduced extracellular striatal and hippocampal monoamine levels, in a concentration dependent manner. The extracellular monoamine level was increased by perfusion with a non-selective adenosine receptor antagonist, caffeine, a selective adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT), and an antiepileptic drug, carbamazepine, whereas adenosine, a selective adenosine A1 receptor agonist, 2-chloro-N6-cyclopentyladenosine (CCPA) reduced extracellular monoamine levels. The former and latter were reduced and enhanced by an increase in [Mg2+]o, respectively. Neither a selective adenosine A2 agonist, N6-[2-(3,5-dimethoxyphenyl)-2-(methylphenyl) ethyl]adenosine (PD125944), nor an antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX), affected extracellular monoamine levels. Under the conditions of adenosine A1 receptor blockade by CPT, adenosine, PD125944 and carbamazepine increased extracellular monoamine levels, whereas caffeine and DMPX decreased them. These stimulatory effects of adenosine, PD125944 and carbamazepine were enhanced by an increase in [Mg2+], whereas the inhibitory effects of caffeine and DMPX were reduced by Mg2+, in a concentration dependent manner. It is concluded that an activation of adenosine A1 and A2 receptors decrease and increase extracellular levels of striatal dopamine, hippocampal dopamine and serotonin, respectively. These whereas the stimulatory effects of adenosine A2 receptor on extracellular levels of monoamine are masked by the inhibitory effects of adenosine A1 receptor. In addition, an increase in [Mg2+]o enhances and reduces the effects of adenosine receptor agonists and antagonists on extracellular monoamine levels, respectively.

Topics: Adenosine; Animals; Biogenic Monoamines; Caffeine; Carbamazepine; Central Nervous System; Central Nervous System Stimulants; Dopamine; Dose-Response Relationship, Drug; Drug Interactions; Hippocampus; Magnesium; Male; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Rats; Rats, Wistar; Receptors, Purinergic P1; Serotonin; Theobromine; Theophylline; Visual Cortex

To clarify differences in the operating mechanisms of adenosine receptor subtypes (A1 and A2), striatal extracellular dopamine levels under various conditions were determined by in vivo microdialysis. Adenosine (50 microM) as well as the selective A1 agonist, 2-chloro-N6-cyclopentyladenosine (CCPA; 1 microM) decreased striatal extracellular dopamine levels, while the selective adenosine A1 antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT; 50 microM) and caffeine (100 microM) increased striatal extracellular dopamine levels. A selective A2a agonist, 2-[4-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamideadeno sine (CGS21680; 10 microM), a selective A2 agonist, N6-[2-(3,5-dimethoxyphenyl)-2-(methylphenyl)ethyl]adenosine (DPMA; 5 microM) and a selective A2 antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX; 10 microM), did not affect extracellular dopamine levels. When the A1 receptor was blocked by CPT, extracellular dopamine levels were increased by adenosine and DPMA, decreased by caffeine as well as DMPX, and unaffected by CGS21680. These results indicate that the stimulatory effects of the A2 receptor on striatal extracellular dopamine levels are masked by the inhibitory effects of the A1 receptor.

Topics: Adenosine; Animals; Antihypertensive Agents; Caffeine; Camptothecin; Dopamine; Enzyme Inhibitors; Extracellular Space; Irinotecan; Male; Microdialysis; Neostriatum; Phenethylamines; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Agonists; Purinergic P1 Receptor Antagonists; Rats; Rats, Wistar; Receptors, Purinergic P1; Theobromine; Vasodilator Agents

The effect of adenosine and related compounds on the proliferation of cultured TM4 cells, a Sertoli-like cell line, has been examined. Adenosine, as well as A1 and A2 adenosine receptor agonists (cyclohexyladenosine and N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl)ethyl]adenosine) inhibited cell proliferation. These effects were prevented by 8-cyclopentyl theophylline, 1,3-dimethyl-propargylxanthine and caffeine, antagonists at the A1, A2 and both receptors, respectively. The xanthines had no effect by themselves and, consistent with this, the bathing medium was found not to contain detectable levels of adenosine. It is concluded that TM4 cell proliferation can be regulated by receptors for adenosine.

Topics: Adenosine; Animals; Caffeine; Cell Division; Cells, Cultured; Male; Mice; Purinergic P1 Receptor Antagonists; Purines; Receptors, Purinergic P1; Sertoli Cells; Theobromine; Theophylline