Some recent investigations revealed that vasodilatory action of adenosine is mainly not mediated by surface A2 receptor and suggested the existence of an intracellular action site. In the present study, we tried to differentiate intracellular from extracellular site of adenosine action in the regulation of coronary flow. In perfused rabbit hearts, concentration-response curve of coronary flow to exogenous adenosine was constructed in the presence or absence of dipyridamole, an inhibitor of transmembrane purine transport. Inhibition of cellular adenosine uptake by dipyridamole suppressed the increase of flow rate while enhancing the decrease in heart rate induced by exogenous adenosine. In another series of experiments, perfused rabbit hearts were subjected to energy deprivation in order to increase the production of endogenous adenosine. Energy deprivation along with dipyridamole administration resulted in higher coronary flow rate. Lower perfusate adenosine concentration was observed along with higher tissue adenosine content in this group. These results implied that coronary flow rate is determined not by interstitial adenosine concentration but by intracellular activity of adenosine. To confirm the effects of dypiridamole in vivo, direct measurement of interstitial adenosine concentration by mycrodialysis along with the assay of intracellular adenosine content was performed after intranenous dipyridamole administration. After dipyridamole infusion, intracellular adenosine content was markedly increased while interstitial adenosine concentration was not altered. In another series of experiments, the right shift of concentration-response curve of adenosine-induced vasodilation by 8-phenyltheophilline, a representative adenosine receptor antagonist, was mostly abolished by prior administration of prazosin, indicating that the influence of 8-PT on the adenosine action is not attributed to the inhibition of A2 receptor but related to the suppression of alpha-adrenoceptor activation. From these results, we concluded that adenosine acts intracellularly to regulate the coronary blood flow.
Adenosine ; Dipyridamole* ; Heart ; Heart Rate ; Prazosin ; Receptors, Purinergic P1 ; Vasodilation*

BACKGROUND/AIMS: Adenosine is an endogenous modulator of nociception. Its role in visceral nociception, particularly in visceral hyperalgesia, has not been studied. The aim of this study was to determine the effects of adenosine receptor agonists in a model of visceral hyperalgesia. METHODS: The visceromotor response (VMR) in rats to colorectal distension (CRD; 80 mmHg, 20 seconds) was quantified by electromyographic recordings from the abdominal musculature. Three hours after the intracolonic administration of zymosan (25 mg/mL, 1 mL), VMRs to CRD were measured before and after either subcutaneous or intrathecal administration of an adenosine receptor agonist. RESULTS: Subcutaneous injection of 5'-N-ethylcarboxyamidoadenosine (NECA; an A1 and A2 receptor agonist), R(-)-N6-(2-phenylisopropyl)-adenosine (R-PIA; a selective A1 receptor agonist), or CGS-21680 hydrochloride (a selective A2a receptor agonist) dose-dependently (10-100 mg/kg) attenuated the VMR to CRD, although hindlimb weakness occurred at the higher doses tested. Intrathecal administration of NECA or R-PIA dose-dependently (0.1-1.0 microgram/kg) decreased the VMR, whereas CGS-21680 hydrochloride was ineffective over the same concentration range. Higher intrathecal doses of the A1/A2 receptor agonist NECA produced motor weakness. CONCLUSIONS: Adenosine receptor agonists are antihyperalgesic, but also produce motor weakness at high doses. However, activation of the spinal A1 receptor significantly attenuates the VMR to CRD without producing motor weakness.
Adenosine ; Adenosine-5'-(N-ethylcarboxamide) ; Animals ; Hindlimb ; Hyperalgesia ; Injections, Subcutaneous ; Nociception ; Purinergic P1 Receptor Agonists ; Rats ; Receptors, Purinergic P1 ; Zymosan

The molecular vibration-activity relationship in the receptor-ligand interaction of adenosine receptors was investigated by structure similarity, molecular vibration, and hierarchical clustering in a dataset of 46 ligands of adenosine receptors. The resulting dendrogram was compared with those of another kind of fingerprint or descriptor. The dendrogram result produced by corralled intensity of molecular vibrational frequency outperformed four other analyses in the current study of adenosine receptor agonism and antagonism. The tree that was produced by clustering analysis of molecular vibration patterns showed its potential for the functional classification of adenosine receptor ligands.
Adenosine* ; Classification ; Dataset ; Dermatoglyphics ; Felodipine* ; Ligands ; Receptors, G-Protein-Coupled ; Receptors, Purinergic P1* ; Subject Headings ; Vibration

As an important neurotransmitter, adenosine displays its functions by acting on the adenosine receptors. Recent studies have shown that the distribution, expression and balance among subtypes of adenosine receptors are closely related with cognitive activities, and changes of adenosine receptors play key roles in neurodegenerative disorders including Alzheimer's disease. It has been pointed out that prolonged activation of adenosine receptors by high level adenosine may lead to the disturbance of balance among adenosine receptor subtypes. This imbalance mainly performed as increased expression of A2a receptor and decreased expression of A1 receptor, and enhancement of the excitatory signals mediated by A2a receptor and weakened inhibitory signals mediated by A1 receptor. Changes of these two subtypes of adenosine receptors may lead to a lot of disorders of neurological activities which developed into dysfunction of cognition to the end. These findings imply that the potential of maintaining the balance among adenosine receptors on the treatment of AD would facilitate both the revealing of the mechanism and the cure of AD.
Adenosine ; physiology ; Alzheimer Disease ; physiopathology ; Humans ; Neurotransmitter Agents ; physiology ; Receptors, Purinergic P1 ; classification ; physiology

The relationship between adenosine receptor (AdoR) and myocardial ischemia (MI), effect of acupuncture for MI and action mechanism of acupuncture improving MI by regulating AdoR are summarized. The existing researches have preliminarily reflected that the improvement of MI treated with acupuncture may be achieved by influencing the expression of AdoR. However, there are still some limitations, e.g. most of the research regimens are single-acupoint, the research results are not entirely consistent and the interaction of AdoRs are ignored, all these need to be further verified and supplemented.
Acupuncture ; Acupuncture Points ; Acupuncture Therapy ; Humans ; Myocardial Ischemia/therapy* ; Receptors, Purinergic P1

The activities of myocardial antioxidant enzymes are known to increase in the hearts preconditioned with the brief episodes of ischemia. This study was undertaken to elucidate the possible involvement of adenosine in the stimulation of myocardial catalase induced by the brief regional ischemia in rabbit hearts. Coronary artery descending the middle anterior wall of left ventricle was occluded for 15 min, followed by 1 hr of reperfusion. Upon reperfusion after the brief ischemia, the activity of catalase increased significantly in both ischemic and non-ischemic parts of myocardium. Pretreatment of the heart with theophylline, a non-specific adenosine receptor blocker, completely abolished the increase of catalase activity in both the ischemic and non-ischemic regions of myocardium. On the other hand, the administration of exogenous adenosine instead of the ischemia failed to increase the catalase activity in in vivo hearts. Moreover, adenosine infusion did not affect the catalase activity in the isolated, perfused hearts either. These results suggest that the endogenous adenosine released from the ischemic myocardium is involved in the activation of catalase induced by brief ischemia, but that adenosine may not be a final direct activator of cellular catalase in the myocardium.
Adenosine* ; Catalase* ; Coronary Vessels ; Hand ; Heart ; Heart Ventricles ; Ischemia* ; Myocardium ; Receptors, Purinergic P1 ; Reperfusion ; Theophylline

As it has been reported that the depolarization induced acetylcholine (ACh) release is modulated by activation of presynaptic A1 adenosine heteroreceptor and various lines of evidence suggest the A2 adenosine receptor is present in the hippocampus. The present study was undertaken to delineate the role of adenosine receptors on the hippocampal ACh release. Slices from the rat hippocampus were equilibrated with (3H)choline and then the release amount of the labelled product, (3H)ACh, which was evoked by electrical stimulation (rectangular pulses, 3 Hz, 2 ms, 24 mA, 5 V/cm-1, 2 min), was measured, and the influence of various adenosine receptor-related agents on the evoked tritium outflow was investigated. And also, the drug-receptor binding assay was performed in order to confirm the presence of A1 and A2 adenosine receptors in the rat hippocampus. N-ethylcarboxamidoadenosine (NECA), a potent adenosine receptor agonist with nearly equal affinity at A1 and A2 adenosine receptors, in concentrations ranging from 1apprx30 muM, decreased the electrically-evoked (3H)ACh release in a concentration-dependent manner without affecting the basal rate of release. And the effect of NECA was significantly inhibited by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 2 micrometer), a selective A1 adenosine receptor antagonist, but was not influenced by 3,7-dimethyl-1-propargylxanthine (DMPX, 5 micrometer, a specific A2 adenosine receptor antagonist. N6-Cyclopentyladenosine (CPA), a selective A1 adenosine receptor agonist, in doses ranging from 0.1 to 10 micrometer, reduced evoked (3H)ACh release in a dose-dependent manner without the change of the basal release. And the effect of CPA was significantly inhibited by 2 micrometer DPCPX treatment. 2-P-(2-carboxyethyl)-phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS-21680C), a potent A2 adenosine receptor agonist, in concentrations ranging from 0.1 to 10 micrometer, did not alter the evoked ACh release. In the drug-receptor binding assay, the binding of (3H)2-chloro-N6-Cyclopentyladenosine ((3H)CCPA) to the- A1 adenosine receptor of rat hippocampal membranes was inhibited by CPA (Ki = 1.22 nM), NECA (Ki=10.17 nM) and DPCPX (Ki-161.86 nM), but not by CGS-21680C (Ki=2,380 nM) and DMPX (Ki-22,367 nM). However, the specific binding of (3H)CGS-21680C to the A2 adenosine receptor was not observed. These results suggest that the A1 adenosine heteroreceptor play an important role in evoked ACh release, but the presence of A2 adenosine receptor is not confirmed in this study.
Acetylcholine* ; Adenosine* ; Adenosine-5'-(N-ethylcarboxamide) ; Animals ; Electric Stimulation ; Hippocampus* ; Membranes ; Rats* ; Receptors, Purinergic P1* ; Tritium

As it has been reported that the depolarization-induced norepinephrine (NE) release is modulated by activation of presynaptic A-1-adenosine heteroreceptor and various lines of evidence indicate that A-2-adenosine receptor also presents in hippocampus, and that the adenosine effect is magnesium dependent, the present study was undertaken to delineate the role of adenosine receptors in the modulation of hippocampal NE release. Slices from the rat hippocampus were equilibrated with (3H)-NE and the release of the labelled product, (3H)-NE, was evoked by electrical stimulation (3 Hz, 5 V cm-1, 2 ms, rectangular pulses), and the influence of various agents on the evoked tritium outflow was investigated. N-6-cyclopentyladenosine (CPA), in concentrations ranging from 0.1 to 10 micrometer, decreased the (3H)-NE release in a dose-dependent manner without changing the basal rate of release, and these effects were significantly inhibited by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 2 micrometer) treatment. When the magnesium concentration was reduced to 0.4 mM or completely removed, the evoked NE release increased along with decreased basal rate of release. In contrast, increasing the magnesium concentrations to 2.4 and 4 mM, decreased the evoked NE release. The CPA effects on evoked NE release were reduced by magnesium removal, but potentiated by 2.4 mM magnesium in the medium. 5-(N-cyclopropyl)-carboxamodiadenosine (CPCA, 1 & 10 micrometer), an A-2-agonist, decreased the evoked tritium outflow, and this effect was also abolished by DPCPX pretreatment. CGS, a powerful A-2-agonist, did not affect the evoked NE release. However, the effects of CPCA and CGS on evoked NE release were significantly increased by pretreatment of DPCPX in the magnesium-free medium. These results indicate that inhibitory effect of A-1-adenosine receptor on NE release is magnesium-dependent, and A-2-receptor may be present in the rat hippocampus.
Adenosine ; Animals ; Electric Stimulation ; Hippocampus* ; Magnesium* ; Norepinephrine* ; Rats* ; Receptors, Purinergic P1 ; Tritium

BACKGROUND: In two-kidney one clip Goldbaltt hypertensive rats(2K1C GHR), clipped kidney may be exposed to low pressure and unclipped kidney to high pressure. In addition, both kidneys may have a different amount of adenosine which is increased by ischemia and plays an important role for renin release. The aim of this study was to invstigate the responsmiveness for renin release to adenosine agonists and antagonist in clipped and unclipped kidney of 2K1C GHR. METHODS: Emplying kidney slices from both unclipped and unclipped kidney of 2K1C GHR, the alteration by adenosine agonists and antagonist of renin release was studied. RESULTS: The renal renin content and basal renin release from unclipped kidney slices were suppressed, whereas those from clipped kidney were augmented Adenosine Al receptor agonist, cyclohexyladenosne(CHA), phenylisopropyl adenosine(PIA) and adenosine caused a decrease in renin release from clipped kidney slices. Adenosine A2 receptor agonist, NECA, and nonspecific adenosine receptor aganist, 2-chloroadenosine(CA) caused an increase in renin release from clipped kidney slices. Adenosine receptor antagonist, 8-phenyltheophylline(8-PT) caused an increase in renin release from clipped kidney slices. In unclipped kidney, however, the renin release in response to NECA, CA or 8-PT was reversed and the decreasing effect of renin release to CHA and adenosine was slightly inereased. CONCLUSION: These results suggest that the responsiveness of adenosine receptors, which may participate in renin release is modified in clipped and unclipped kidney of 2K1C GHR.
Adenosine* ; Adenosine-5'-(N-ethylcarboxamide) ; Animals ; Hypertension, Renovascular ; Ischemia ; Kidney ; Rats* ; Receptors, Adenosine A2 ; Receptors, Purinergic P1 ; Renin*

OBJECTIVES: To examine possible modulators of the ion transport through the apical membrane of the nasal polyps. METHODS: The study was conducted using the freshly-excised nasal polyps from the patients with chronic sinusitis. A voltage-sensitive vibrating probe technique was introduced to monitor the short-circuit current across the apical membrane of the polyp at 37degrees C. RESULTS: In the presence of amiloride, Adenosine 5'-triphosphate induced 4,4'-Diisothiocyanatostilbene-2,2'-disulfonic acidsensitive chloride current. Uridine 5'-diphosphate was less potent than Uridine 5'-triphosphate, and adenosine increased chloride secretion, which was blocked by the antagonist, 8-(p-sulfophenyl) theophylline on adenosine receptor. Based on the pharmacologic profiles, multiple purinergic receptors, including P2Y(2), P2Y(6), and P1 receptors, were functionally expressed. However, P2X receptor agonists (alpha,beta-methyleneadenosine 5'-triphosphate and 2'- & 3'-O-[4-benzoyl-benzoyl] adenosine 5'-triphosphate), Cystic fibrosis conductance regulator (CFTR) activator (genistein), nitric oxide substrate (L-arginine), and nitric oxide donor (sodium nitroprusside) had no significant effect on the short circuit current. CONCLUSION: Among tested drugs, P2Y receptor agonists were major modulators of ion transport in nasal polyps in situ.
Adenosine ; Amiloride ; Cystic Fibrosis ; Genistein ; Humans ; Ion Transport ; Membranes ; Nasal Polyps ; Nitric Oxide ; Organothiophosphorus Compounds ; Polyps ; Receptors, Purinergic ; Receptors, Purinergic P1 ; Sinusitis ; Theophylline ; Tissue Donors ; Uridine