BACKGROUND: Analgesic tolerance to opioids has been described in both experimental and clinical conditions, which may limit their clinical utility. This study investigated the effects of intrathecal adenosine A1 receptor agonist (R-PIA) on spinal morphine tolerance. METHODS: SD rats were given intrathecal injections of saline 10microliter, R-PIA 10microgram, morphine 10microgram, or R-PIA plus morphine combinations for 7 days (R-PIA given for days 1-7; days 1-3; or days 5-7). Antiallodynic testing using von Frey filaments was carried out before and 30 minutes after the drug injection. On day 8, an antiallodynic dose-response curve was constructed and the 50% effective dose (ED(50)) for morphine (given alone) was calculated for each study group. RESULTS: The coinjection group of R-PIA with morphine blocked the development of tolerance, as shown by the preservation of morphine antiallodynia over 7 days the concomitant decrease in the ED(50) values on day 8, compared with the morphine-alone group. Although additive analgesia over days 1-7 cannot be ruled out, the reductions of the ED(50) in the R-PIA and morphine combination group suggest some suppression of tolerance. CONCLUSIONS: These results suggest that intrathecal R-PIA prevents the development of spinal opioid tolerance. Future studies will be needed to examine the respective roles of supraspinal and peripheral sites of R-PIA and morphine interaction, and to investigate the mechanisms underlying the action of R-PIA on opioid tolerance.
Adenosine A1 Receptor Agonists* ; Adenosine* ; Analgesia ; Analgesics, Opioid ; Animals ; Hyperalgesia ; Injections, Spinal ; Models, Animal* ; Morphine* ; Pain, Postoperative* ; Rats* ; Receptor, Adenosine A1*

Adenosine receptors (AR) play an important role in the regulation processes for body temperature and vigilance states. During our previous studies, we noticed that aminophylline (a non-selective, blood-brain-barrier penetrably AR antagonist) could attenuate the effects of YZG-330 [(2R,3S,4R,5R)-2-(hydroxymethyl-5-(6-(((R)-1-phenylpropyl)amino)-9H-purin-9-yl)tetrahydrofuran-3, 4-diol] on lowering the body temperature. Hereby, we focused ourselves on the character of thermal regulation effect of YZG-330 in mice and tried to specify the receptor subtype via giving typical adenosine receptor antagonists. The results showed that both of the magnitude and lasting time of the effect that YZG-330 played on decreasing body temperature are in a dose-dependent manner: within the next 3 hour after intragastric administration (ig) of 0.25, 1 or 4 mg . kg-1 YZG-330, the extreme values on body temperature decreasing were (1.2 ± 0.3) °C, (3.6 ± 0.4) °C (P<0.001) and (7.4±0.5) °C (P<0.001), separately; whereas the duration that body temperature below 34 °C were 0, (10±5) and (153±4) min, separately. Adenosine A1 receptor (A1R) antagonist (DPCPX) could effectively reverse YZG-330's effect on decreasing body temperature, with intraperitoneal administration of DPCPX (5 mg . kg-1) 20 min prior than YZG-330 (4 mg.kg-1, ig), the extreme value on body temperature decreasing was (3.5 ± 0.7) °C (P<0.001), the duration that body temperature below 34 °C was (8±6) min (P<0.001). However, adenosine A2a receptor antagonist, SCH-58261, did not show any influence on the effects of YZG-330 at all. Combined with the fact that 8-SPT (a non-selective, blood-brain-barrier impenetrably AR antagonist) did not reverse the effect of YZG-330, we come to the conclusion that central-adenosine A, receptor plays a significant role on the thermal regulation effect of YZG-330.
Adenosine ; analogs & derivatives ; pharmacology ; Adenosine A1 Receptor Antagonists ; pharmacology ; Animals ; Body Temperature Regulation ; drug effects ; Mice ; Pyrimidines ; pharmacology ; Receptor, Adenosine A1 ; physiology ; Triazoles ; pharmacology ; Xanthines ; pharmacology

Adenosine A1 receptor (ADORA1) has a neuromodulatory activity in early stage of brain development. Recent studies have been suggested that a deficit in adenosinergic function may be a key factor in the pathophysiology of schizophrenia. To determine the genetic association between ADORA1 gene polymorphism and schizophrenia in Korean population, we genotyped single nucleotide polymorphism (SNP) (rs10920568, A102A, exon5) in the ADORA1 gene by using the direct sequencing. Among SNPs in the coding region of ADORA1, only one synonymous SNP's heterozygosity (rs10920568) is more than 0.05. Three hundred three control and 284 schizophrenia subjects were recruited. For the analysis of genetic data, EM algorithm, SNPStats, SNPAnalyzer, and Helixtree programs were used. Multiple logistic regression analysis with the codominant, dominant, and recessive models was performed. The genotype frequencies of rs10920568 showed statistically significant difference between schizophrenic patients and healthy control subjects. The rs10920568 SNP of ADORA1 was weakly associated with schizophrenia in the dominant model (p=0.04, odds ratio=0.70, 95% confidence interval =0.50~0.98). The result suggests that the ADORA1 gene may be associated with schizophrenia.
Adenosine ; Brain ; Clinical Coding ; Genotype ; Humans ; Logistic Models ; Polymorphism, Single Nucleotide ; Receptor, Adenosine A1 ; Schizophrenia

The effects of adenosine, adenosine A1 receptor antagonist (DPCPX), or NMDA receptor antagonist (APV) on the spontaneous release of (3H)-5-hydroxytryptamine ((3H)-5-HT) during normoxic/normoglycemic or hypoxic/hypoglycemic period were studied in the rat hippocampal slices. The hippocampus was obtained from the rat brain and sliced 400 mum thickness with the tissue slicer. After 30 min's preincubation in the normal buffer, the slices were incubated for 30 min in a buffer containing (3H)-5-HT (0.1 muM, 74 muCi/8 ml) for uptake, and washed. To measure the release of (3H)-5-HT into the buffer, the incubation medium was drained off and refilled every ten minutes through sequence of 14 tubes. Induction of glucose/oxygen deprivation (GOD; medium depleting glucose and gassed with 95% N2/5% CO2) was done in 6th and 7th tube. The radioactivities in each buffer and the tissue were counted using liquid scintillation counter and the results were expressed as a percentage of the total radioactivities. When slices were exposed to GOD for 20 mins, the spontaneous release of (3H)-5-HT was markedly increased and this increase of (3H)-5-HT release was blocked by adenosine (10 muM) or DL-2-amino-5-phosphonovaleric acid (APV; 30 muM). Adenosine A1 receptor specific antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) exacerbate GOD-induced increase of spontaneous release of (3H)-5-HT. These results suggest that Adenosine may play a role in the GOD-induced spontaneous release of (3H)-5-HT through adenosine A1 receptor activity.
Adenosine* ; Animals ; Brain ; Glucose ; Hippocampus ; N-Methylaspartate ; Radioactivity ; Rats* ; Receptor, Adenosine A1 ; Scintillation Counting

BACKGORUND: A nerve ligation injury may produce a pain syndrome including mechanical allodynia. Usually the antiallodynic effect of morphine is diminished in a neuropathic rat model. However, in a previous study, spinal morphine was found to have an antiallodynic effect in a neuropathic rat model. Therefore, the present study was performed to observe the mechanical antiallodynic effects of spinal morphine and R-PiA, and to investigate the relationship between the two. METHODS: Male SD rats were prepared by tightly ligating the left L5 and L6 spinal nerve and by implanting a lumbar intrathecal catheter. in study 1, each of the 5 groups (morphine at 3 or 10mug, adenosine A1 receptor agonist (R-PiA) at 3 or 10mug, or saline) were administered intrathecally to examine changes in the mechanical allodynia threshold. in study 2, selective adenosine A1 receptor antagonist (DPCPX 10mug) was administered to investigate the reversal of the mechanical antiallodynic effect in the 4 treated groups. in study 3, we observed the pretreatment effect of DPCPX 10mug. The mechanical allodynic thresholds for left hindpaw withdrawal to von Frey hairs were assessed and converted to %MPE. RESULTS: in study 1, the mechanical allodynic threshold was significantly increased in a similar pattern by intrathecal morphine (3, 10mug) and R-PiA (3, 10mug) (P<0.05). in study 2, the allodynic threshold of morphine was insignificantly decreased by intrathecal DPCPX pretreatment. The mechanical allodynic threshold of R-PiA 3mug was decreased by intrathecal DPCPX (P<0.05). in study 3, the antiallodynic effect of morphine was not influenced by DPCPX pretreatment. CONCLUSiONS: intrathecal morphine and R-PiA produced the antiallodynic effect. The antiallodynic effect of morphine was slightly decreased by DPCPX 10mug. Therefore, it was suggested that the antiallodynic effect of morphine might be, at least in part, mediated by adenosine in a rat model of spinal nerve ligation.
Adenosine ; Animals ; Catheters ; Hair ; Humans ; Hyperalgesia ; Ligation* ; Male ; Models, Animal ; Morphine* ; Rats* ; Receptor, Adenosine A1 ; Receptors, Purinergic P1 ; Spinal Nerves*

Luteolin, a widespread flavonoid, has been known to have neuroprotective activity against various neurologic diseases such as epilepsy, and Alzheimer’s disease. However, little information is available regarding the hypnotic effect of luteolin. In this study, we evaluated the hypnotic effect of luteolin and its underlying mechanism. In pentobarbital-induced sleeping mice model, luteolin (1, and 3 mg/kg, p.o.) decreased sleep latency and increased the total sleep time. Through electroencephalogram (EEG) and electromyogram (EMG) recording, we demonstrated that luteolin increased non-rapid eye movement (NREM) sleep time and decreased wake time. To evaluate the underlying mechanism, we examined the effects of various pharmacological antagonists on the hypnotic effect of luteolin. The hypnotic effect of 3 mg/kg of luteolin was not affected by flumazenil, a GABAA receptor-benzodiazepine (GABAAR-BDZ) binding site antagonist, and bicuculine, a GABAAR-GABA binding site antagonist. On the other hand, the hypnotic effect of 3 mg/kg of luteolin was almost completely blocked by caffeine, an antagonist for both adenosine A1 and A2A receptor (A1R and A2AR), 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX), an A1R antagonist, and SCH-58261, an A2AR antagonist. From the binding affinity assay, we have found that luteolin significantly binds to not only A1R but also A2AR with IC₅₀ of 1.19, 0.84 μg/kg, respectively. However, luteolin did not bind to either BDZ-receptor or GABAAR. From these results, it has been suggested that luteolin has hypnotic efficacy through A1R and A2AR binding.
Adenosine ; Animals ; Binding Sites ; Caffeine ; Electroencephalography ; Epilepsy ; Eye Movements ; Flumazenil ; Hand ; Hypnotics and Sedatives ; Luteolin ; Mice ; Receptor, Adenosine A1 ; Receptor, Adenosine A2A ; Sleep Initiation and Maintenance Disorders

OBJECTIVETo observe the impact of adenosine A1 receptor stimulation on extracellular signal-regulated kinase 1/2 (ERK1/2) signal pathways on angiotensin II (AngII) stimulated cardiomyocytes of neonatal rats in vitro.

METHODSCardiomyocytes of neonatal rats were cultured in vitro. Cardiomyocytes hypertrophy was induced by AngII (0.1 µmol/L). The antihypertrophic effect of adenosine A1 receptor stimulation via adenosine A1 receptor agonist R-PIA (1 µmol/L) was observed in the presence or absence of ERK1/2 inhibitor 1, 4-Diamino-2, 3-dicyano-1, 4-bis(o-aminophenylmercapto) butadiene (U0126) 1 µmol/L, PKC inhibitor Ro-31-8220 (50 nmol/L), and pertussis toxin (PTX, 5 mg/L). The total protein content was assayed by the method of Lowry. The expression of mRNA of atrial natriuretic peptide (ANP) was determined by RT-PCR. [Ca(2+)]i was measured by confocal microscope using Fluo-3/AM as fluorescent indicator. The relative expression of ERK1/2 was determined by Western blot.

RESULTSCompared with normal control group, AngII induced significant cardiomyocyte hypertrophy. Compared with AngII group, R-PIA significantly inhibited AngII-induced increase of the protein content, cardiomyocytes volume and expression of ERK1/2, calcium ion fluorescence intensity, similar as U0126 and Ro-31-8220. The inhibitory effects on AngII induced cardiomyocytes hypertrophy of R-PIA were lost when preincubated with PTX.

CONCLUSIONAdenosine A1 receptor can inhibit AngII induced cardiomyocyte hypertrophy through downregulating ERK signal pathways and reducing intracellular Ca(2+).

Adenosine A1 Receptor Agonists ; pharmacology ; Angiotensin II ; pharmacology ; Animals ; Calcium ; metabolism ; Cardiomegaly ; chemically induced ; prevention & control ; Cells, Cultured ; Female ; MAP Kinase Signaling System ; Male ; Myocytes, Cardiac ; drug effects ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley ; Receptor, Adenosine A1 ; drug effects ; metabolism

A brief episode of ischemia and reperfusion termed 'ischemic preconditioning' has been established as rendering muscle tolerance to damage during a subsequent prolonged ischemia. The effects of ischemic preconditioning in the cardiac muscle is related to the stimulation of adenosine A1 receptor and the opening of KATP channel. The effect and mechanism of ischemic preconditioning in the skeletal muscle is not known clearly. The author performed the present study to investigate the effect and the mechanisms of ischemic preconditioning by measuring the SOD immunoreactivities on timely reperfused ischemic muscles. The healthy Sprague -Dawley rats weighing from 200 g to 250 g were used as experimental animals. Under pentobarbital (50 mg/kg) anesthesia, lower abdominal incision was done and left common iliac artery was ligated by using vascular clamp for 2 hours. Rectus femoris muscles were obtained at 0 hour, 1 hour, 2 hours, 6 hours, 12 hours, 24 hours, 48 hours and 72 hours of reperfusion. The group of ischemic preconditioning underwent three episodes of 5 minute occlusion and 5 minute reperfusion of common iliac artery followed by 2 hours of ischemia and timely reperfusion. Adenosine (50 microgram/kg) or pinacidil (1 mg/kg) were administered intravenously before ischemia and 2 hours of ischemia and timely reperfusion was done. 10 microM thick cryosections in all groups were obtained. The immunoreactivities of SOD were observed by use of antihuman Cu,Zn -and Mn -SOD antibodies. The results obtained were as follows. 1. The immunoreactivities of SOD in the rectus femoris muscles of rats increased after ischemic preconditioning. The patterns of the changes in immunoreactivities of Cu, Zn -and Mn -SOD were similar at the muscle fibers with large section area or small section area. 2. After the treatment of adenosine, the immunoreactivities of Cu, Zn -SOD in the group of 2 hours and 24 hours reperfusion and the immunoreactivities of Mn -SOD in the group of 24 hours reperfusion increased. After the treatment of pinacidil, the immunoreactivities of Mn - SOD increased and the immunoreactivities of Cu, Zn -SOD are similar to normal control rat. 3. After 2 hours of ischemia the immunoreactivities of SOD were similar to normal control rat. The immunoreactivities of Cu, Zn -SOD in the group of 1 hour, 2 hours and 24 hours reperfusion and those of Mn -SOD in all groups of reperfusion increased. 4. In the group of 2 hours ischemia and timely reperfusion with ischemic preconditioning, the immunoreactivities of SOD in the muscle fiber with large section area decreased and those of SOD in the muscle fibers with small section area increased in comparison with the group of 2 hours and timely reperfusion. The pattern of change between immunoreactivities of Cu,Zn -and Mn -SOD in each muscle fiber were similar. 5. After the treatment of adenosine, the immunoreactivities of SOD increased in the group of 1 hour, 2 hours, 6 hours and 12 hours reperfusion. After the treatment of pinacidil, the immunoreactivities of SOD increased in the group of 1 hour, 2 hours, 6 hours, 12 hours and 24 hours reperfusion. Consequently, these results suggest that the immunoreactivities of SOD increase after 2 hours of ischemia and timely reperfusion with ischemic preconditioning. The effect of ischemic preconditioning is related to opening of KATP channel partly.
Adenosine ; Anesthesia ; Animals ; Antibodies ; Iliac Artery ; Ischemia* ; Ischemic Preconditioning ; Muscle, Skeletal ; Muscles* ; Myocardium ; Pentobarbital ; Pinacidil* ; Quadriceps Muscle* ; Rats* ; Receptor, Adenosine A1 ; Reperfusion*

A variety of G protein coupled receptors (GPCRs) are expressed in the presynaptic terminals of central and peripheral synapses and play regulatory roles in transmitter release. The patch-clamp whole-cell recording technique, applied to the calyx of Held presynaptic terminal in brainstem slices of rodents, has made it possible to directly examine intracellular mechanisms underlying the GPCR-mediated presynaptic inhibition. At the calyx of Held, bath-application of agonists for GPCRs such as GABAB receptors, group III metabotropic glutamate receptors (mGluRs), adenosine A1 receptors, or adrenaline alpha2 receptors, attenuate evoked transmitter release via inhibiting voltage-activated Ca2+ currents without affecting voltage-activated K+ currents or inwardly rectifying K+ currents. Furthermore, inhibition of voltage-activated Ca2+ currents fully explains the magnitude of GPCR-mediated presynaptic inhibition, indicating no essential involvement of exocytotic mechanisms in the downstream of Ca2+ influx. Direct loadings of G protein beta gamma subunit (G beta gamma) into the calyceal terminal mimic and occlude the inhibitory effect of a GPCR agonist on presynaptic Ca2+ currents (IpCa), suggesting that G beta gammamediates presynaptic inhibition by GPCRs. Among presynaptic GPCRs glutamate and adenosine autoreceptors play regulatory roles in transmitter release during early postnatal period when the release probability (p) is high, but these functions are lost concomitantly with a decrease in p during postnatal development.
Adenosine ; Autoreceptors ; Brain Stem ; Epinephrine ; Glutamic Acid ; GTP-Binding Proteins* ; Patch-Clamp Techniques ; Presynaptic Terminals ; Receptor, Adenosine A1 ; Receptors, G-Protein-Coupled* ; Receptors, Metabotropic Glutamate ; Rodentia ; Synapses

BACKGROUND: Several types of receptors are found at neuromuscular presynaptic membranes. Presynaptic inhibitory A1 and facilitatory A2A receptors mediate different modulatory functions on acetylcholine release. This study investigated whether adenosine A1 receptor agonist contributes to the first twitch tension (T1) of train-of-four (TOF) stimulation depression and TOF fade during rocuronium-induced neuromuscular blockade, and sugammadex-induced recovery. METHODS: Phrenic nerve-diaphragm tissues were obtained from 30 adult Sprague-Dawley rats. Each tissue specimen was randomly allocated to either control group or 2-chloroadenosine (CADO, 10 μM) group. One hour of reaction time was allowed before initiating main experimental data collection. Loading and boost doses of rocuronium were sequentially administered until > 95% depression of the T1 was achieved. After confirming that there was no T1 twitch tension response, 15 min of resting time was allowed, after which sugammadex was administered. Recovery profiles (T1, TOF ratio [TOFR], and recovery index) were collected for 1 h and compared between groups. RESULTS: There were statistically significant differences on amount of rocuronium (actually used during experiment), TOFR changes during concentration-response of rocuronium (P = 0.04), and recovery profiles (P < 0.01) of CADO group comparing with the control group. However, at the initial phase of this experiment, dose-response of rocuronium in each group demonstrated no statistically significant differences (P = 0.12). CONCLUSIONS: The adenosine A1 receptor agonist (CADO) influenced the TOFR and the recovery profile. After activating adenosine receptor, sugammadex-induced recovery from rocuronium-induced neuromuscular block was delayed.
2-Chloroadenosine ; Acetylcholine ; Adenosine* ; Adult ; Data Collection ; Depression ; Humans ; Membranes ; Neuromuscular Blockade* ; Neuromuscular Junction ; Neuromuscular Nondepolarizing Agents ; Rats, Sprague-Dawley ; Reaction Time ; Receptor, Adenosine A1 ; Receptors, Purinergic P1*