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Sergi Ferre - One of the best experts on this subject based on the ideXlab platform.
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computer assisted image analysis of caveolin 1 involvement in the internalization process of adenosine a2a dopamine d2 receptor heterodimers
Journal of Molecular Neuroscience, 2005Co-Authors: Susanna Genedani, Sergi Ferre, Kjell Fuxe, Maria Torvinen, Diego Guidolin, Giuseppina Leo, Monica Filaferro, Amina S Woods, Luigi F AgnatiAbstract:A functional aspect of horizontal molecular networks has been investigated experimentally, namely the heteromerization between adenosine A2A and dopamine D2 receptors and the possible role of caveolin-1 in the co-trafficking of these molecular complexes. This study has been carried out by means of computer-assisted image analysis procedure of laser images of membrane immunoreactivity of caveolin-1, A2A, D1, and D2 receptors obtained in two clones of Chinese hamster ovary cells one transfected with A2A and dopamine D1 receptors and the other one with A2A and D2 receptors. Cells were treated for 3 h with 10 microM D1 receptor agonist SKF 38393, 50 microM D2-D3 receptor agonist quinpirole, and 200 nM A2A receptor agonist CGS 21680. In A2A-D1-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D1 receptors and treatment with SKF 38393 induced internalization of caveolin-1 and D1 receptors, with a preferential internalization of D1 receptors colocalized with caveolin-1. In A2A-D2-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D2 receptors and either CGS 21680 or quinpirole treatment induced internalization of caveolin-1 and A2A and D2 receptors, with a preferential internalization of A2A and D2 receptors colocalized with caveolin-1. The results suggest that A2A and D2 receptors and caveolin-1 likely interact forming a macrocomplex that internalizes upon agonist treatment. These observations are discussed in the frame of receptor oligomerization and of the possible functional role of caveolin-1 in the process of co-internalization and, hence, in controlling the permanence of receptors at the plasma membrane level (prerequisite for receptor mosaic organization and plastic adjustments) and in the control of receptor desensitization.
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involvement of adenosine a1 and a2a receptors in the adenosinergic modulation of the discriminative stimulus effects of cocaine and methamphetamine in rats
Journal of Pharmacology and Experimental Therapeutics, 2003Co-Authors: Zuzana Justinova, Sergi Ferre, Marcello Solinas, Pavan N Segal, K Antoniou, Lara A Pappas, Jena L Highkin, Jorg Hockemeyer, Patrik Munzar, Steven R GoldbergAbstract:Adenosine, by acting on adenosine A1 and A2A receptors, is known to antagonistically modulate dopaminergic neurotransmission. We have recently reported that nonselective adenosine receptor antagonists (caffeine and 3,7-dimethyl-1-propargylxanthine) can partially substitute for the discriminative-stimulus effects of methamphetamine. In the present study, by using more selective compounds, we investigated the involvement of A1 and A2A receptors in the adenosinergic modulation of the discriminative-stimulus effects of both cocaine and methamphetamine. The effects of the A1 receptor agonist N 6-cyclopentyladenosine (CPA; 0.01–0.1 mg/kg) and antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT; 1.3–23.7 mg/kg) and the A2A receptor agonist 2- p -(2-carboxyethyl)phenethylamino-5′- N -ethylcarboxamidoadenosine hydrochloride (CGS 21680; 0.03–0.18 mg/kg) and antagonist 3-(3-hydroxypropyl)-8-(3-methoxystyryl)-7-methyl-1-propargylxanthin phosphate disodium salt (MSX-3; 1–56 mg/kg) were evaluated in rats trained to discriminate either 1 mg/kg methamphetamine or 10 mg/kg cocaine from saline under a fixed-ratio 10 schedule of food presentation. The A1 and A2A receptor antagonists (CPT and MSX-3) both produced high levels of drug-lever selection when substituted for either methamphetamine or cocaine and significantly shifted dose-response curves of both psychostimulants to the left. Unexpectedly, the A2A receptor agonist CGS 21680 also produced drug-appropriate responding (although at lower levels) when substituted for the cocaine-training stimulus, and both CGS 21680 and the A1 receptor agonist CPA significantly shifted the cocaine dose-response curve to the left. In contrast, both agonists did not produce significant levels of drug-lever selection when substituted for the methamphetamine-training stimulus and failed to shift the methamphetamine dose-response curve. Therefore, adenosine A1 and A2A receptors appear to play important but differential roles in the modulation of the discriminative-stimulus effects of methamphetamine and cocaine.
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metabotropic glutamate mglu5 receptor mediated modulation of the ventral striopallidal gaba pathway in rats interactions with adenosine a 2a and dopamine d 2 receptors
Neuroscience Letters, 2002Co-Authors: Zaida Diazcabiale, Kjell Fuxe, Meritxell Vivo, Alberto Del Arco, William T Oconnor, Michael K Harte, Christa E Muller, Emili Martinez, Patrizia Popoli, Sergi FerreAbstract:Interactions between subtypes of dopamine, glutamate and adenosine receptors seem to play an important integrative role in the function of striatal gamma-aminobutyric acid (GABA)ergic efferent neurons. Recent behavioral and biochemical studies suggest the existence of specific interactions between adenosine A2A receptors (A(2A)R), dopamine D2 receptors (D2R) and the group I metabotropic mGlu5 receptors (mGlu5R) in the dorsal striatum. The dual-probe approach in vivo microdialysis technique in freely moving rats was used to study the role of mGlu5R/A2AR/D2R interactions in the modulation of the ventral striopallidal GABA pathway. Perfusion of a selective mGlu5R agonist (CHPG) in the nucleus accumbens facilitated GABA release in the ipsilateral ventral pallidum. This effect was strongly potentiated by co-perfusion with the A2AR agonist CGS 21680. Co-perfusion with the D2R agonist quinpirole counteracted the increase in pallidal GABA levels induced by CGS 21680 and by CGS 21680 plus CHPG. These results demonstrate that mGlu5R/A2AR/D2R interactions play an important modulatory role in the function of the ventral striopallidal GABA pathway, which might have implications for the treatment of schizophrenia and drug addiction.
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the selective mglu5 receptor agonist chpg inhibits quinpirole induced turning in 6 hydroxydopamine lesioned rats and modulates the binding characteristics of dopamine d2 receptors in the rat striatum interactions with adenosine a2a receptors
Neuropsychopharmacology, 2001Co-Authors: Patrizia Popoli, Kjell Fuxe, Antonella Pezzola, Rosaria Reggio, Maria Torvinen, Annita Pintor, Laura Scarchilli, Sergi FerreAbstract:In 6-hydroxydopamine-lesioned rats, the selective mGlu5 receptor agonist (RS)-2-Cholro-5-Hydroxyphenylglycine (CHPG, 1-6 μg/10 μl intracerebroventricularly) significantly inhibited contralateral turning induced by quinpirole and, to a lesser extent, that induced by SKF 38393. The inhibitory effects of CHPG on quinpirole-induced turning were significantly potentiated by an adenosine A2A receptor agonist (CGS 21680, 0.2 mg/kg IP) and attenuated by an A2A receptor antagonist (SCH 58261, 1 mg/kg IP). In rat striatal membranes, CHPG (100–1,000 nM) significantly reduced the affinity of the high-affinity state of D2 receptors for the agonist, an effect potentiated by CGS 21680 (30 nM). These results show the occurrence of functional interactions among mGlu5, adenosine A2A, and dopamine D2 receptors in the regulation of striatal functioning, and suggest that mGlu5 receptors may be regarded as alternative/integrative targets for the development of therapeutic strategies in the treatment of Parkinson's disease.
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stimulation of adenosine a2 receptors induces catalepsy
Neuroscience Letters, 1991Co-Authors: Sergi Ferre, Antonia Rubio, Kjell FuxeAbstract:The central administration of the adenosine A2 agonist CGS 21680 induced catalepsy in the rat. This effect was counteracted by the previous systemic administration of the adenosine antagonist theophylline or the D2 agonist BHT-920. These results are in agreement with the view that adenosine A2 receptors regulate central dopamine D2 transmission and underline the potential antipsychotic activity of A2 agonists.
Kjell Fuxe - One of the best experts on this subject based on the ideXlab platform.
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computer assisted image analysis of caveolin 1 involvement in the internalization process of adenosine a2a dopamine d2 receptor heterodimers
Journal of Molecular Neuroscience, 2005Co-Authors: Susanna Genedani, Sergi Ferre, Kjell Fuxe, Maria Torvinen, Diego Guidolin, Giuseppina Leo, Monica Filaferro, Amina S Woods, Luigi F AgnatiAbstract:A functional aspect of horizontal molecular networks has been investigated experimentally, namely the heteromerization between adenosine A2A and dopamine D2 receptors and the possible role of caveolin-1 in the co-trafficking of these molecular complexes. This study has been carried out by means of computer-assisted image analysis procedure of laser images of membrane immunoreactivity of caveolin-1, A2A, D1, and D2 receptors obtained in two clones of Chinese hamster ovary cells one transfected with A2A and dopamine D1 receptors and the other one with A2A and D2 receptors. Cells were treated for 3 h with 10 microM D1 receptor agonist SKF 38393, 50 microM D2-D3 receptor agonist quinpirole, and 200 nM A2A receptor agonist CGS 21680. In A2A-D1-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D1 receptors and treatment with SKF 38393 induced internalization of caveolin-1 and D1 receptors, with a preferential internalization of D1 receptors colocalized with caveolin-1. In A2A-D2-cotransfected cells, caveolin-1 was found to colocalize with both A2A and D2 receptors and either CGS 21680 or quinpirole treatment induced internalization of caveolin-1 and A2A and D2 receptors, with a preferential internalization of A2A and D2 receptors colocalized with caveolin-1. The results suggest that A2A and D2 receptors and caveolin-1 likely interact forming a macrocomplex that internalizes upon agonist treatment. These observations are discussed in the frame of receptor oligomerization and of the possible functional role of caveolin-1 in the process of co-internalization and, hence, in controlling the permanence of receptors at the plasma membrane level (prerequisite for receptor mosaic organization and plastic adjustments) and in the control of receptor desensitization.
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involvement of adenosine a1 and a2a receptors in the motor effects of caffeine after its acute and chronic administration
Neuropsychopharmacology, 2003Co-Authors: Marzena Karczkubicha, Christa E Muller, Katerina Antoniou, Anton Terasmaa, Davide Quarta, Marcello Solinas, Zuzana Justinova, Antonella Pezzola, Rosaria Reggio, Kjell FuxeAbstract:The involvement of adenosine A1 and A2A receptors in the motor effects of caffeine is still a matter of debate. In the present study, counteraction of the motor-depressant effects of the selective A1 receptor agonist CPA and the A2A receptor agonist CGS 21680 by caffeine, the selective A1 receptor antagonist CPT, and the A2A receptor antagonist MSX-3 was compared. CPT and MSX-3 produced motor activation at the same doses that selectively counteracted motor depression induced by CPA and CGS 21680, respectively. Caffeine also counteracted motor depression induced by CPA and CGS 21680 at doses that produced motor activation. However, caffeine was less effective than CPT at counteracting CPA and even less effective than MSX-3 at counteracting CGS 21680. On the other hand, when administered alone in habituated animals, caffeine produced stronger motor activation than CPT or MSX-3. An additive effect on motor activation was obtained when CPT and MSX-3 were coadministered. Altogether, these results suggest that the motor-activating effects of acutely administered caffeine in rats involve the central blockade of both A1 and A2A receptors. Chronic exposure to caffeine in the drinking water (1.0 mg/ml) resulted in tolerance to the motor effects of an acute administration of caffeine, lack of tolerance to amphetamine, apparent tolerance to MSX-3 (shift to the left of its ‘bell-shaped’ dose–response curve), and true cross-tolerance to CPT. The present results suggest that development of tolerance to the effects of A1 receptor blockade might be mostly responsible for the tolerance to the motor-activating effects of caffeine and that the residual motor-activating effects of caffeine in tolerant individuals might be mostly because of A2A receptor blockade.
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metabotropic glutamate mglu5 receptor mediated modulation of the ventral striopallidal gaba pathway in rats interactions with adenosine a 2a and dopamine d 2 receptors
Neuroscience Letters, 2002Co-Authors: Zaida Diazcabiale, Kjell Fuxe, Meritxell Vivo, Alberto Del Arco, William T Oconnor, Michael K Harte, Christa E Muller, Emili Martinez, Patrizia Popoli, Sergi FerreAbstract:Interactions between subtypes of dopamine, glutamate and adenosine receptors seem to play an important integrative role in the function of striatal gamma-aminobutyric acid (GABA)ergic efferent neurons. Recent behavioral and biochemical studies suggest the existence of specific interactions between adenosine A2A receptors (A(2A)R), dopamine D2 receptors (D2R) and the group I metabotropic mGlu5 receptors (mGlu5R) in the dorsal striatum. The dual-probe approach in vivo microdialysis technique in freely moving rats was used to study the role of mGlu5R/A2AR/D2R interactions in the modulation of the ventral striopallidal GABA pathway. Perfusion of a selective mGlu5R agonist (CHPG) in the nucleus accumbens facilitated GABA release in the ipsilateral ventral pallidum. This effect was strongly potentiated by co-perfusion with the A2AR agonist CGS 21680. Co-perfusion with the D2R agonist quinpirole counteracted the increase in pallidal GABA levels induced by CGS 21680 and by CGS 21680 plus CHPG. These results demonstrate that mGlu5R/A2AR/D2R interactions play an important modulatory role in the function of the ventral striopallidal GABA pathway, which might have implications for the treatment of schizophrenia and drug addiction.
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the selective mglu5 receptor agonist chpg inhibits quinpirole induced turning in 6 hydroxydopamine lesioned rats and modulates the binding characteristics of dopamine d2 receptors in the rat striatum interactions with adenosine a2a receptors
Neuropsychopharmacology, 2001Co-Authors: Patrizia Popoli, Kjell Fuxe, Antonella Pezzola, Rosaria Reggio, Maria Torvinen, Annita Pintor, Laura Scarchilli, Sergi FerreAbstract:In 6-hydroxydopamine-lesioned rats, the selective mGlu5 receptor agonist (RS)-2-Cholro-5-Hydroxyphenylglycine (CHPG, 1-6 μg/10 μl intracerebroventricularly) significantly inhibited contralateral turning induced by quinpirole and, to a lesser extent, that induced by SKF 38393. The inhibitory effects of CHPG on quinpirole-induced turning were significantly potentiated by an adenosine A2A receptor agonist (CGS 21680, 0.2 mg/kg IP) and attenuated by an A2A receptor antagonist (SCH 58261, 1 mg/kg IP). In rat striatal membranes, CHPG (100–1,000 nM) significantly reduced the affinity of the high-affinity state of D2 receptors for the agonist, an effect potentiated by CGS 21680 (30 nM). These results show the occurrence of functional interactions among mGlu5, adenosine A2A, and dopamine D2 receptors in the regulation of striatal functioning, and suggest that mGlu5 receptors may be regarded as alternative/integrative targets for the development of therapeutic strategies in the treatment of Parkinson's disease.
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stimulation of adenosine a2 receptors induces catalepsy
Neuroscience Letters, 1991Co-Authors: Sergi Ferre, Antonia Rubio, Kjell FuxeAbstract:The central administration of the adenosine A2 agonist CGS 21680 induced catalepsy in the rat. This effect was counteracted by the previous systemic administration of the adenosine antagonist theophylline or the D2 agonist BHT-920. These results are in agreement with the view that adenosine A2 receptors regulate central dopamine D2 transmission and underline the potential antipsychotic activity of A2 agonists.
Dasiel O Borrotoescuela - One of the best experts on this subject based on the ideXlab platform.
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acute cocaine treatment enhances the antagonistic allosteric adenosine a2a dopamine d2 receptor receptor interactions in rat dorsal striatum without increasing significantly extracellular dopamine levels
Pharmacological Reports, 2020Co-Authors: Wilber Romerofernandez, Zilong Zhou, Sarah Beggiato, Karolina Wydra, Malgorzata Filip, Sergio Tanganelli, Dasiel O BorrotoescuelaAbstract:Antagonistic adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) receptor–receptor interactions have previously been demonstrated in A2AR–D2R heteroreceptor complexes in the rat dorsal striatum. They mainly involve a reduction of affinity in the high-affinity component of the D2R agonist binding site upon activation in vivo of the A2AR by an A2AR agonist. Upon cocaine self-administration, this antagonistic A2AR–D2R interaction disappeared in the dorsal striatum. In the current experiments, it was tested whether such modifications in the antagonistic A2AR–D2R receptor–receptor interactions can develop also after an acute systemic injection of a low cocaine dose (1 mg/kg; sc). Microdialysis experiments indicated that acute cocaine did not significantly alter the extracellular dopamine levels in the dorsal striatum of the awake Wistar rats. Competition dopamine receptor binding experiments demonstrated that in the acute cocaine group, the A2AR agonist CGS-21680 produced significantly larger increases in the D2R Ki, High values (reduction of high-affinity) versus the saline-injected (i.e. control) group. Furthermore, in the dorsal striatum membrane preparation from acute cocaine-injected rats, CGS-21680 also produced significant increases in the D2R Ki, Low values (reduction of low-affinity) and in the proportion of D2Rs in the high-affinity state (RH). Such significant effects were not observed with CGS-21680 in the control group. The molecular mechanism involved in the acute cocaine-induced increase in the antagonistic allosteric A2AR–D2R receptor–receptor interactions may be an increased formation of higher-order complexes A2AR–D2R-sigma1R in which cocaine by binding to the sigma1R protomer also allosterically enhances the inhibitory A2AR–D2R interaction in this receptor complex.
J A Ribeiro - One of the best experts on this subject based on the ideXlab platform.
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adenosine a2a receptors activation facilitates neuromuscular transmission in the pre symptomatic phase of the sod1 g93a als mice but not in the symptomatic phase
PLOS ONE, 2014Co-Authors: Filipe Nascimento, Paula A. Pousinha, Rui Gomes, Ana M Sebastiao, Alexandra Marcal Correia, J A RibeiroAbstract:Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease leading to motor neuron dysfunction resulting in impairment of neuromuscular transmission. A2A adenosine receptors have already been considered as a potential therapeutical target for ALS but their neuromodulatory role at the neuromuscular junction in ALS remains to be clarified. In the present work, we evaluated the effects of A2A receptors on neuromuscular transmission of an animal model of ALS: SOD1(G93A) mice either in the pre-symptomatic (4–6 weeks old) or in the symptomatic (12–14 weeks old) stage. Electrophysiological experiments were performed obtaining intracellular recordings in Mg2+ paralyzed phrenic nerve-hemidiaphragm preparations. Endplate potentials (EPPs), quantal content (q. c.) of EPPs, miniature endplate potentials (MEPPs) and giant miniature endplate potential (GMEPPs) were recorded. In the pre-symptomatic phase of the disease (4–6 weeks old mice), the selective A2A receptor agonist, CGS 21680, significantly enhanced (p<0.05 Unpaired t-test) the mean amplitude and q.c. of EPPs, and the frequency of MEPPs and GMEPPs at SOD1(G93A) neuromuscular junctions, the effect being of higher magnitude (p<0.05, Unpaired t-test) than age-matched control littermates. On the contrary, in symptomatic mice (12–14 weeks old), CGS 21680 was devoid of effect on both the amplitude and q.c. of EPPs and the frequency of MEPPs and GMEPPs (p<0.05 Paired t-test). The results herein reported clearly document that at the neuromuscular junction of SOD1(G93A) mice there is an exacerbation of A2A receptor-mediated excitatory effects at the pre-symptomatic phase, whereas in the symptomatic phase A2A receptor activation is absent. The results thus suggest that A2A receptors function changes with ALS progression.
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a2a adenosine receptor facilitation of neuromuscular transmission influence of stimulus paradigm on calcium mobilization
Journal of Neurochemistry, 2002Co-Authors: Paulo Correiadesa, M A Timoteo, J A RibeiroAbstract:The influence of stimulus pulse duration on calcium mobilization triggering facilitation of evoked [(3)H]acetylcholine ([(3)H]ACh) release by the A(2A) adenosine receptor agonist CGS 21680C was studied in the rat phrenic nerve-hemidiaphragm. The P-type calcium channel blocker omega-agatoxin IVA (100 nM) decreased [(3)H]ACh release evoked with pulses of 0.04-ms duration, whereas nifedipine (1 microM) inhibited transmitter release with pulses of 1-ms duration. Depletion of intracellular calcium stores by thapsigargin (2 microM) decreased [(3)H]ACh release evoked by pulses of 1 ms, an effect observed even in the absence of extracellular calcium. With short (0.04-ms) stimulation pulses, when P-type calcium influx triggered transmitter release, facilitation of [(3)H]ACh release by CGS 21680C (3 nM) was attenuated by both thapsigargin (2 microM) and nifedipine (1 microM). With longer stimuli (1 ms), a situation in which both thapsigargin-sensitive internal stores and L-type channels are involved in ACh release, pretreatment with either omega-agatoxin IVA (100 nM) or nifedipine (1 microM) reduced the facilitatory effect of CGS 21680C (3 nM). The results suggest that A(2A) receptor activation facilitates ACh release from motor nerve endings through alternatively mobilizing the available calcium pools (thapsigargin-sensitive internal stores and/or P- or L-type channels) that are not committed to the release process in each stimulation condition.
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evidence that the presynaptic a2a adenosine receptor of the rat motor nerve endings is positively coupled to adenylate cyclase
Naunyn-schmiedebergs Archives of Pharmacology, 1994Co-Authors: Paulo Correiadesa, J A RibeiroAbstract:The action of the A2a-adenosine analogue, CGS 21680C, on electrically evoked [3H]acetylcholine ([3H]-ACh) release, and its interaction with forskolin (an activator of adenylate cyclase), MDL 12,330A (an irreversible inhibitor of adenylate cyclase), rolipram (an inhibitor of cyclic AMP specific phosphodiesterase), dibutyryl- (db-cAMP) and 8-bromo- (8-Br-cAMP) cyclic AMP analogues (substances that mimic intracellular actions of cyclic AMP), were investigated using rat phrenic nerve-hemidiaphragm preparations. CGS 21680C facilitated [3H]ACh release. Forskolin (but not 1,9-dideoxy forskolin), rolipram, db-cAMP and 8-Br-cAMP also increased evoked neurotransmitter release in a concentration-dependent manner. When the evoked [3H]-ACh release that is dependent on stimulation of the adenylate cyclase/cyclic AMP transduction system was supramaximally stimulated by these compounds, CGS 21680 C (3 μmol/l) could not further increase [3H]-ACh release. Phosphodiesterase inhibition with low concentrations (⩽ 30 μmol/l) of rolipram significantly potentiated the augmenting effect of CGS 21680C (1 μmol/l) on evoked [3H]ACh release. MDL 12,330A (an irreversible inhibitor of adenylate cyclase) decreased evoked [3H]-ACh release. The irreversible blocking action of MDL 12,330A on [3H]-ACh release was overcome by by-passing cyclase activation with db-cAMP and 8-Br-cAMP, but could not be overcome with FSK or CGS 21680 C. The inhibitory effect of MDL 12,330A on evoked [3H]-ACh release was not mimicked by nifedipine. It is concluded that the increase in [3H]-ACh release caused by CGS 21680C results from activation of an A2a-adenosine receptor positively linked to the adenylate cyclase/cyclic AMP system.
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inhibitory and excitatory effects of adenosine receptor agonists on evoked transmitter release from phrenic nerve endings of the rat
British Journal of Pharmacology, 1991Co-Authors: Paulo Correiadesa, Ana M Sebastiao, J A RibeiroAbstract:1. The effects of the adenosine analogues, 5'-N-ethyl-carboxamide adenosine (NECA), R-N6-phenylisopropyladenosine (R-PIA), 2-chloroadenosine (CADO), and CGS 21680C on electrically evoked tritium outflow from preparations loaded with [3H]-choline and on evoked endplate potentials (e.p.ps), as well as the ability of the xanthines, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and PD 115,199 to antagonize the effects of the adenosine analogues, were investigated in phrenic nerve-diaphragm preparations. 2. NECA, R-PIA and CADO decreased, in a concentration-dependent manner, the evoked tritium outflow from preparations loaded with [3H]-choline. NECA and R-PIA were about equipotent and more potent than CADO. 3. DPCPX shifted to the right in a near parallel fashion the concentration-response curve for the inhibitory effect of R-PIA on evoked tritium outflow. 4. In the presence of DPCPX, NECA increased, rather than decreased, evoked tritium outflow. PD 115,119 antagonized, in a concentration-dependent manner, this excitatory effect of NECA. 5. CGS 21680C, in low nanomolar concentrations, increased evoked tritium outflow, an effect also antagonized by PD 115,119. 6. CGS 21680C increased, and R-PIA decreased, the amplitude of e.p.ps recorded from preparations paralysed with tubocurarine. Both effects could be observed in the same endplate. 7. It is concluded that both inhibitory (probably A1) and excitatory (probably A2) adenosine receptors coexist at the rat neuromuscular junction, modulating the evoked release of acetylcholine.
Bertil B Fredholm - One of the best experts on this subject based on the ideXlab platform.
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binding of the prototypical adenosine a2a receptor agonist cgs 21680 to the cerebral cortex of adenosine a1 and a2a receptor knockout mice
British Journal of Pharmacology, 2004Co-Authors: Luisa V Lopes, Bertil B Fredholm, Nelson Rebola, Bjorn Johansson, Linda Halldner, Catherine Ledent, Jian Fan Chen, Rodrigo A CunhaAbstract:2-p-(2-carboxyethylphenethylamino-5′-ethylcarboxamidoadenosine) (CGS 21680) is considered the reference compound to study adenosine A2A receptors. However, CGS 21680 binding in the cerebral cortex, where adenosine A1 receptors are predominant, displays a mixed A2A/A1 receptor pharmacology. We now use adenosine A1 and A2A receptor knockout mice to investigate the characteristics of cortical [3H]CGS 21680 binding. [3H]CGS 21680 binding to the cerebral cortex was strongly reduced in adenosine A1 receptor knockout mice, but only slightly reduced in A2A receptor knockout mice compared with the corresponding wild-type littermates. Another selective A2A receptor ligand, [3H]-5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine ([3H]SCH 58261), displayed a saturable binding to mouse cortical membranes, albeit with a binding density 20 times lower than that of striatal membranes, and this [3H]SCH58261 binding was abolished in both striatal and cortical membranes of A2A receptor knockout mice and unchanged in A1 receptor knockout mice. The presence of A2A receptors in cortical neurons was further confirmed by Western blot in mouse cortical nerve terminal membranes. It is concluded that, although A2A receptors are present in the cerebral cortex, the purportedly selective A2A receptor agonist [3H]CGS 21680 binds in the cerebral cortex to an entity that requires the presence of adenosine A1 receptors. Thus, CGS 21680 should be used with care in all preparations where adenosine A1 receptors out-number A2A receptors. British Journal of Pharmacology (2004) 141, 1006–1014. doi:10.1038/sj.bjp.0705692
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adenosine a2a receptor facilitation of hippocampal synaptic transmission is dependent on tonic a1 receptor inhibition
Neuroscience, 2002Co-Authors: Luisa V Lopes, Bertil B Fredholm, Rodrigo A Cunha, Bjorn Kull, Joaquim A. RibeiroAbstract:Abstract Adenosine tonically inhibits synaptic transmission through actions at A 1 receptors. It also facilitates synaptic transmission, but it is unclear if this facilitation results from pre- and/or postsynaptic A 2A receptor activation or from indirect control of inhibitory GABAergic transmission. The A 2A receptor agonist, CGS 21680 (10 nM), facilitated synaptic transmission in the CA1 area of rat hippocampal slices (by 14%), independent of whether or not GABAergic transmission was blocked by the GABA A and GABA B receptor antagonists, picrotoxin (50 μM) and CGP 55845 (1 μM), respectively. CGS 21680 (10 nM) also inhibited paired-pulse facilitation by 12%, an effect prevented by the A 2A receptor antagonist, ZM 241385 (20 nM). These effects of CGS 21680 (10 nM) were occluded by adenosine deaminase (2 U/ml) and were made to reappear upon direct activation of A 1 receptors with N 6 -cyclopentyladenosine (CPA, 6 nM). CGS 21680 (10 nM) only facilitated (by 17%) the K + -evoked release of glutamate from superfused hippocampal synaptosomes in the presence of 100 nM CPA. This effect of CGS 21680 (10 nM), in contrast to the isoproterenol (30 μM) facilitation of glutamate release, was prevented by the protein kinase C inhibitors, chelerythrine (6 μM) and bisindolylmaleimide (1 μM), but not by the protein kinase A inhibitor, H-89 (1 μM). Isoproterenol (30 μM), but not CGS 21680 (10–300 nM), enhanced synaptosomal cAMP levels, indicating that the CGS 21680-induced facilitation of glutamate release involves a cAMP-independent protein kinase C activation. To discard any direct effect of CGS 21680 on adenosine A 1 receptor, we also show that in autoradiography experiments CGS 21680 only displaced the adenosine A 1 receptor antagonist, 1,3-dipropyl-8-cyclopentyladenosine ([ 3 H]DPCPX, 0.5 nM) with an EC 50 of 1 μM in all brain areas studied and CGS 21680 (30 nM) failed to change the ability of CPA to displace DPCPX (1 nM) binding to CHO cells stably transfected with A 1 receptors. Our results suggest that A 2A receptor agonists facilitate hippocampal synaptic transmission by attenuating the tonic effect of inhibitory presynaptic A 1 receptors located in glutamatergic nerve terminals. This might be a fine-tuning role for adenosine A 2A receptors to allow frequency-dependent plasticity phenomena without compromising the A 1 receptor-mediated neuroprotective role of adenosine.
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activation of adenosine a2a and dopamine d1 receptors stimulates cyclic amp dependent phosphorylation of darpp 32 in distinct populations of striatal projection neurons
Neuroscience, 1998Co-Authors: Per Svenningsson, Bertil B Fredholm, Maria Lindskog, F Rognoni, Paul Greengard, Gilberto FisoneAbstract:Abstract In the striatum, adenosine A 2A and dopamine D 1 receptors are segregated in striatopallidal and striatonigral projection neurons, respectively. In this study, we have examined the effects of activating adenosine A 2A and dopamine D 1 receptors on the state of phosphorylation of DARPP-32 (dopamine- and cyclic AMP-regulated phosphoprotein of mol. wt 32,000), a potent endogenous regulator of protein phosphatase-1 that is highly expressed in striatal medium-sized spiny neurons. In rat striatal slices, the D 1 receptor agonist SKF 81297 and the A 2A receptor agonist CGS 21680 transiently increased the levels of phosphorylated DARPP-32 in a concentration-dependent manner. In the same preparation, the two agonists were also able to induce a significant increase in cyclic AMP formation. When striatal slices were incubated with a combination of CGS 21680 and SKF 81297, the effects of the two agonists on both DARPP-32 phosphorylation and cyclic AMP formation were additive. The maximal effects of SKF 81297 and CGS 21680 on DARPP-32 phosphorylation were of similar magnitude, and were completely abolished by the cyclic AMP-dependent protein kinase inhibitor, Rp-cAMPS. The present results show that DARPP-32 phosphorylation in the striatum is stimulated by adenosine, acting on A 2A receptors, and dopamine, acting on D 1 receptors, and that cyclic AMP is the mediator in both cases. Our data also suggest that dopamine and adenosine regulate the state of phosphorylation of DARPP-32 in distinct sub-populations of medium-sized spiny neurons expressing dopamine D 1 and adenosine A 2A receptors, respectively.
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distribution of adenosine receptors in the postmortem human brain an extended autoradiographic study
Synapse, 1997Co-Authors: Per Svenningsson, Hakan Hall, Goran Sedvall, Bertil B FredholmAbstract:Whole-hemisphere sections from six subjects were used in a quantitative autoradiographic study to characterize and to investigate the distribution of adenosine receptors, using [3H]DPCPX, [3H]CGS 21680, and [3H]SCH 58261 as radioligands. [3H]DPCPX-binding showed the pharmacology expected for adenosine A1 receptors and is therefore taken to mirror adenosine A1 receptors. Adenosine A1 receptors were widely distributed, with the highest densities in the stratum radiatum/pyramidale of the hippocampal region CA 1. Adenosine A1 receptors were nonhomogeneously distributed in nucleus caudatus, globus pallidus, and cortical areas: In the cingulate and frontal cortex the deep layers showed the highest labeling, while in the occipital, parietal, temporal, and insular cortex it was highest in the superficial layers. In addition, we found very high levels of adenosine A1 receptors in structures known to be important for cholinergic transmission, especially the septal nuclei. The Bmax values and KD values for [3H]DPCPX-binding in stratum radiatum/pyramidale of CA1 and the superficial layer of insular cortex were 598 and 430 fmol/mg gray matter and 9.9 and 14.2 nM, respectively. [3H]CGS 21680-binding was multiphasic, but showed the pharmacology expected for adenosine A2A receptors and was taken to represent them. Adenosine A2A receptors were abundant in putamen, nucleus caudatus, nucleus accumbens, and globus pallidus pars lateralis. Specific [3H]CGS 21680-binding was also found in certain thalamic nuclei and throughout the cerebral cortex. The adenosine A2A receptor antagonist radioligand [3H]SCH 58261 was also found to label these extrastriatal structures. Thus, adenosine A2A receptors seem to be more widely distributed in the human brain than previously recognized. Synapse 27:322–335, 1997. © 1997 Wiley-Liss, Inc.
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evidence for high affinity binding sites for the adenosine a2a receptor agonist 3h cgs 21680 in the rat hippocampus and cerebral cortex that are different from striatal a2a receptors
Naunyn-schmiedebergs Archives of Pharmacology, 1996Co-Authors: Rodrigo A Cunha, M D Constantino, Ana M Sebastiao, Bjorn Johansson, Bertil B FredholmAbstract:The binding of the adenosine A2A receptor selective agonist 2-[4-(2-p-carboxyethyl) phenylamino]-5′-N-ethylcarboxamidoadenosine (CGS 21680) to the rat hippocampal and cerebral cortical membranes was studied and compared with that to striatal membranes. [3H] CGS 21680, in the concentration range tested (0.2–200 nM), bound to a single site with a Kd of 58 nM and a Bmax of 353 fmol/mg protein in the hippocampus, and with a Kd of 58 nM and a Bmax of 264 fmol/mg protein in the cortex; in the striatum, the single high-affinity [3H] CGS 21680 binding site had a Kd of 17 nM and a Bmax of 419 fmol/mg protein. Both guanylylimidodiphosphate (100 μM) and Na+ (100 mM) reduced the affinity of [3H] CGS 21680 binding in the striatum by half and virtually abolished [3H] CGS 21680 binding in the hippocampus and cortex. The displacement curves of [3H] CGS 21680 binding with 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), N6-cyclohexyladenosine (CHA), 5′-N-ethyl-carboxamidoadenosine (NECA) and 2-chloroadenosine (CADO) were biphasic in the hippocampus and cortex as well as in the striatum. The predominant [3H]CGS 21680 binding site in the striatum (80%) had a pharmacological profile compatible with A2A receptors and was also present in the hippocampus and cortex, representing 10–25% of [3H]CGS 21680 binding. The predominant [3H]CGS 21680 binding site in the hippocampus and cortex had a pharmacological profile distinct from A2A receptors: the relative potency order of adenosine antagonists DPCPX, 1,3-dipropyl8-{4-[(2-aminoethyl)amino]carbonylmethyloxyphenyl} xanthine (XAC), 8-(3-chlorostyryl) caffeine (CSC), and (E)-1,3-dipropyl-8-(3,4-dimethoxystyryl)-methylxanthine (KF 17,837) as displacers of [3H] CGS 21680 (5 nM) binding in the hippocampus and cerebral cortex was DPCPX > XAC ≫ CSC ≈ KF 17,837, and the relative potency order of adenosine agonists CHA, NECA, CADO, 2-[(2-aminoethylamino)carbonylethylphenylethylamino]-5′-N-ethylcar-boxamidoadenosine (APEC), and 2-phenylaminoadenosine (CV 1808) was CHA ≈ NECA ⩾ CADO > APEC ≈ CV1808 > CGS 21680. In the presence of DPCPX (20 nM), [3H] CGS 21680 (0.2-200 nM) bound to a site (A2A-like) with a Kd of 20 nM and a Bmax of 56 fmol/mg protein in the hippocampus and with a Kd of 22 nM and a Bmax of 63 fmol/mg protein in the cortex. In the presence of CSC (200 nM), [3H]CGS 21680 (0.2–200 nM) bound to a second high-affinity site with a Kd of 97 nM and a Bmax of 255 fmol/mg protein in the hippocampus and with a Kd of 112 nM and a Bmax of 221 fmol/mg protein in the cortex. Two pharmacologically distinct [3H]CGS 21680 binding sites were found in synaptosomal membranes of the hippocampus and cortex and in the striatum, one corresponding to A2A receptors and the other to the second high-affinity [3H]CGS 21680 binding site. In contrast, the pharmacology of [3H]CHA binding was similar in synaptosomal membranes of the three brain areas. The present results establish the existence of at least two high-affinity [3H]CGS 21680 binding sites in the CNS and demonstrate that the [3H]CGS 21680 binding site predominant in the hippocampus and cerebral cortex has different binding characteristics from the classic A2A adenosine receptor, which predominates in the striatum.