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Rendón-Ochoa EA, Padilla-Orozco M, Calderon VM, Avilés-Rosas VH, Hernández-González O, Hernández-Flores T, Perez-Ramirez MB, Palomero-Rivero M, Galarraga E, Bargas J. Dopamine D 2 and Adenosine A 2A Receptors Interaction on Ca 2+ Current Modulation in a Rodent Model of Parkinsonism. ASN Neuro 2022; 14:17590914221102075. [PMID: 36050845 PMCID: PMC9178983 DOI: 10.1177/17590914221102075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Adenosine A1 and A2A receptors are expressed in striatal projection neurons (SPNs). A1 receptors are located in direct (dSPN) and indirect SPNs (iSNP). A2A receptors are only present in iSPNs. Dopamine D2 receptors are also expressed in iSPNs and interactions between D2 and A2A receptors have received attention. iSPNs activity increases during parkinsonism (PD) and A2A receptors may be responsible by enhancing Ca2+ currents (iCa2+). Therefore, A2A receptors blockade is a therapeutic approach. We asked whether A2A receptors need the interaction with D2 receptors (D2R) to exert their actions. By using isolated and identified iSPNs to avoid indirect influences, we show that D2R action habilitates A2A receptors (A2AR) modulation. iCa2+ through voltage gated Ca2+ channels (CaV) was used as a signal to observe this interaction. Voltage-clamp recordings in acutely dissociated iSPNs, current-clamp recordings in slices and calcium imaging in transgenic A2A-Cre mice, showed that D2R reduction in iCa2+ endows A2AR to restore iCa2+ on iSPNs showing an antagonistic interaction between D2 and A2A receptors. A2A receptors were blocked by the antagonist istradefylline, however, this blockade differed in control and dopamine-depleted iSPNs: istradefylline reduced D2R modulation in parkinsonian animals as compared to controls. Calcium imaging recordings show that istradefylline occludes D2R actions in the parkinsonian circuitry and this effect depends on the order of drugs application. Thus, while D2 activation enables A2A receptors action, blockade of A2AR induces a reduction in the action of D2 agonists, confirming a complex interaction. Summary Statement A2A receptor required previous D2 receptor activation to modulate Ca2+ currents. Istradefylline decreases pramipexole modulation on Ca2+ currents. Istradefylline reduces A2A + neurons activity in striatial microcircuit, but pramipexole failed to further reduce neuronal activity.
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Affiliation(s)
- Ernesto Alberto Rendón-Ochoa
- Laboratorio de Psicofarmacología, Unidad de Investigación Interdisciplinaria y de Ciencias de la Salud y Educación, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Tlalnepantla, Mexico
| | - Montserrat Padilla-Orozco
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - Vladimir Melesio Calderon
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - Victor Hugo Avilés-Rosas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - Omar Hernández-González
- Facultad de Medicina, Departamento dé Fisiología, Universidad Nacional Autónoma de México, Circuito Exterior s/n Ciudad Universitaria, Ciudad de Mexico, Mexico
| | - Teresa Hernández-Flores
- Brain Mechanism for behavior Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - María Belén Perez-Ramirez
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - Marcela Palomero-Rivero
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - Elvira Galarraga
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
| | - José Bargas
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico
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Valenti O, Zambon A, Boehm S. Orchestration of Dopamine Neuron Population Activity in the Ventral Tegmental Area by Caffeine: Comparison With Amphetamine. Int J Neuropsychopharmacol 2021; 24:832-841. [PMID: 34278424 PMCID: PMC8538898 DOI: 10.1093/ijnp/pyab049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 06/30/2021] [Accepted: 07/16/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Among psychostimulants, the dopamine transporter ligands amphetamine and cocaine display the highest addictive potential; the adenosine receptor antagonist caffeine is most widely consumed but less addictive. Psychostimulant actions of amphetamine were correlated with its ability to orchestrate ventral tegmental dopamine neuron activity with contrasting shifts in firing after single vs repeated administration. Whether caffeine might impinge on dopamine neuron activity has remained elusive. METHODS Population activity of ventral tegmental area dopamine neurons was determined by single-unit extracellular recordings and set in relation to mouse behavior in locomotion and conditioned place preference experiments, respectively. RESULTS A single dose of caffeine reduced population activity as did amphetamine and the selective adenosine A2A antagonist KW-6002, but not the A1 antagonist DPCPX. Repeated administration of KW-6002 or amphetamine led to drug-conditioned place preference and to unaltered or even enhanced population activity. Recurrent injection of caffeine or DPCPX, in contrast, failed to cause conditioned place preference and persistently reduced population activity. Subsequent to repetitive drug administration, re-exposure to amphetamine or KW-6002, but not to caffeine or DPCPX, was able to reduce population activity. CONCLUSIONS Behavioral sensitization to amphetamine is attributed to persistent activation of ventral tegmental area dopamine neurons via the ventral hippocampus. Accordingly, a switch from acute A2A receptor-mediated reduction of dopamine neuron population activity to enduring A1 receptor-mediated suppression is correlated with tolerance rather than sensitization in response to repeated caffeine intake.
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Affiliation(s)
- Ornella Valenti
- Division of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University Vienna, Vienna, Austria,Correspondence: Assoc. Prof. Ornella Valenti, Schwarzspanierstrasse 17, 1090 Vienna, Austria ()
| | - Alice Zambon
- Division of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
| | - Stefan Boehm
- Division of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University Vienna, Vienna, Austria
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López-Ramírez G, Sánchez-Zavaleta R, Ávalos-Fuentes A, José Sierra J, Paz-Bermúdez F, Leyva-Gómez G, Segovia Vila J, Cortés H, Florán B. D 2 autoreceptor switches CB 2 receptor effects on [ 3 H]-dopamine release in the striatum. Synapse 2019; 74:e22139. [PMID: 31610050 DOI: 10.1002/syn.22139] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 09/26/2019] [Accepted: 10/10/2019] [Indexed: 12/28/2022]
Abstract
CB2 receptors (CB2 R) are expressed in midbrain neurons. To evidence the control of dopamine release in dorsal striatum by CB2 R, we performed experiments of [3 H]-dopamine release in dorsal striatal slices. We found a paradoxical increase in K+ -induced [3 H]-dopamine release by CB2 R activation with GW 833972A and JWH 133 two selective agonist. To understand the mechanism involved, we tested for a role of the D2 autoreceptor in this effect; because in pallidal structures, the inhibitory effect of CB1 receptors (CB1 R) on GABA release is switched to a stimulatory effect by D2 receptors (D2 R). We found that the blockade of D2 autoreceptors with sulpiride prevented the stimulatory effect of CB2 R activation; in fact, under this condition, CB2 R decreased dopamine release, indicating the role of the D2 autoreceptor in the paradoxical increase. We also found that the effect occurs in nigrostriatal terminals, since lesions with 6-OH dopamine in the middle forebrain bundle prevented CB2 R effects on release. In addition, D2 -CB2 R interaction promoted cAMP accumulation, and the increase in [3 H]-dopamine release was prevented by PKA blockade. D2 -CB2 R coprecipitation and proximity ligation assay studies indicated a close interaction of receptors that could participate in the observed effects. Finally, intrastriatal injection of CB2 R agonist induced contralateral turning in amphetamine-treated rats, which was prevented by sulpiride, indicating the role of the interaction in motor behavior. Thus, these data indicate that the D2 autoreceptor switches, from inhibitory to stimulatory, the CB2 R effects on dopamine release, involving the cAMP → PKA pathway in nigrostriatal terminals.
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Affiliation(s)
- Gabriel López-Ramírez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Rodolfo Sánchez-Zavaleta
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Arturo Ávalos-Fuentes
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Juan José Sierra
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Francisco Paz-Bermúdez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Gerardo Leyva-Gómez
- Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México, Mexico
| | - José Segovia Vila
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
| | - Hernán Cortés
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, Ciudad de México, Mexico
| | - Benjamín Florán
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México, Mexico
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Morales-Figueroa GE, Rivera-Ramírez N, González-Pantoja R, Escamilla-Sánchez J, García-Hernández U, Galván EJ, Arias-Montaño JA. Adenosine A 2A and histamine H 3 receptors interact at the cAMP/PKA pathway to modulate depolarization-evoked [ 3H]-GABA release from rat striato-pallidal terminals. Purinergic Signal 2018; 15:85-93. [PMID: 30565027 DOI: 10.1007/s11302-018-9638-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/20/2018] [Indexed: 02/06/2023] Open
Abstract
We previously reported that the activation of histamine H3 receptors (H3Rs) selectively counteracts the facilitatory action of adenosine A2A receptors (A2ARs) on GABA release from rat globus pallidus (GP) isolated nerve terminals (synaptosomes). In this work, we examined the mechanisms likely to underlie this functional interaction. Three possibilities were explored: (a) changes in receptor affinity for agonists induced by physical A2AR/H3R interaction, (b) opposite actions of A2ARs and H3Rs on depolarization-induced Ca2+ entry, and (c) an A2AR/H3R interaction at the level of adenosine 3',5'-cyclic monophosphate (cAMP) formation. In GP synaptosomal membranes, H3R activation with immepip reduced A2AR affinity for the agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride hydrate (CGS-21680) (Ki control 4.53 nM; + immepip 9.32 nM), whereas A2AR activation increased H3R affinity for immepip (Ki control 0.63 nM; + CGS-21680 0.26 nM). Neither A2AR activation nor H3R stimulation modified calcium entry through voltage-gated calcium channels in GP synaptosomes, as evaluated by microfluorometry. A2AR-mediated facilitation of depolarization-evoked [2,3-3H]-γ-aminobutyric acid ([3H]-GABA) release from GP synaptosomes (130.4 ± 3.6% of control values) was prevented by the PKA inhibitor H-89 and mimicked by the adenylyl cyclase activator forskolin or by 8-Bromo-cAMP, a membrane permeant cAMP analogue (169.5 ± 17.3 and 149.5 ± 14.5% of controls). H3R activation failed to reduce the facilitation of [3H]-GABA release induced by 8-Bromo-cAMP. In GP slices, A2AR activation stimulated cAMP accumulation (290% of basal) and this effect was reduced (- 75%) by H3R activation. These results indicate that in striato-pallidal nerve terminals, A2ARs and H3Rs interact at the level of cAMP formation to modulate PKA activity and thus GABA release.
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Affiliation(s)
- Guadalupe-Elide Morales-Figueroa
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México
| | - Nayeli Rivera-Ramírez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México
| | - Raúl González-Pantoja
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México
| | - Juan Escamilla-Sánchez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México
| | - Ubaldo García-Hernández
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México
| | - Emilio J Galván
- Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, 07360, MÉXICO, México
| | - José-Antonio Arias-Montaño
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, AV. IPN 2508, Ciudad de México, México.
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Sánchez-Zavaleta R, Cortés H, Avalos-Fuentes JA, García U, Segovia Vila J, Erlij D, Florán B. Presynaptic cannabinoid CB2 receptors modulate [ 3 H]-Glutamate release at subthalamo-nigral terminals of the rat. Synapse 2018; 72:e22061. [PMID: 30022523 DOI: 10.1002/syn.22061] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 07/12/2018] [Accepted: 07/13/2018] [Indexed: 11/08/2022]
Abstract
Recent studies suggested the expression of CB2 receptors in neurons of the CNS, however, most of these studies have only explored one aspect of the receptors, i.e., expression of protein, messenger RNA, or functional response, and more complete studies appear to be needed to establish adequately their role in the neuronal function. Electron microscopy studies showed the presence of CB2r in asymmetric terminals of the substantia nigra pars reticulata (SNr), and its mRNA appeared is expressed in the subthalamic nucleus. Here, we explore the expression, source, and functional effects of such receptors by different experimental approaches. Through PCR and immunochemistry, we showed mRNA and protein for CB2rs in slices and primary neuronal cultures from subthalamus. GW833972A, GW405833, and JHW 133, three CB2r agonists dose-dependent inhibited K+ -induced [3 H]-Glutamate release in slices of SNr, and the two antagonist/inverse agonists, JTE-907 and AM630, but not AM281, a CB1r antagonist, prevented GW833972A effect. Subthalamus lesions with kainic acid prevented GW833972A inhibition on release and decreased CB2r protein in nigral synaptosomes, thus nigral CB2rs originate in subthalamus. Inhibition of [3 H]-Glutamate release was PTX- and gallein-sensitive, suggesting a Giβγ -mediated effect. P/Q Ca2+ -type channel blocker, ω-Agatoxin-TK, also inhibited the [3 H]-Glutamate release, this effect was occluded with GW833972A inhibition, indicating that the βγ subunit effect is exerted on Ca2+ channel activity. Finally, microinjections of GW833972A in SNr induced contralateral turning. Our data showed that presynaptic CB2rs inhibit [3 H]-Glutamate release in subthalamo-nigral terminals by P/Q-channels modulation through the Giβγ subunit and suggested their participation in motor behavior.
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Affiliation(s)
- Rodolfo Sánchez-Zavaleta
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City, México
| | - Hernán Cortés
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, Ciudad de México, México
| | - José Arturo Avalos-Fuentes
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City, México
| | - Ubaldo García
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City, México
| | - José Segovia Vila
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City, México
| | - David Erlij
- Department of Physiology, SUNY Downstate Medical Center, Brooklyn, New York
| | - Benjamín Florán
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México City, México
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Diao HL, Xue Y, Han XH, Wang SY, Liu C, Chen WF, Chen L. Adenosine A 2A Receptor Modulates the Activity of Globus Pallidus Neurons in Rats. Front Physiol 2017; 8:897. [PMID: 29163226 PMCID: PMC5682020 DOI: 10.3389/fphys.2017.00897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 10/24/2017] [Indexed: 12/23/2022] Open
Abstract
The globus pallidus is a central nucleus in the basal ganglia motor control circuit. Morphological studies have revealed the expression of adenosine A2A receptors in the globus pallidus. To determine the modulation of adenosine A2A receptors on the activity of pallidal neurons in both normal and parkinsonian rats, in vivo electrophysiological and behavioral tests were performed in the present study. The extracellular single unit recordings showed that micro-pressure administration of adenosine A2A receptor agonist, CGS21680, regulated the pallidal firing activity. GABAergic neurotransmission was involved in CGS21680-induced modulation of pallidal neurons via a PKA pathway. Furthermore, application of two adenosine A2A receptor antagonists, KW6002 or SCH442416, mainly increased the spontaneous firing of pallidal neurons, suggesting that endogenous adenosine system modulates the activity of pallidal neurons through adenosine A2A receptors. Finally, elevated body swing test (EBST) showed that intrapallidal microinjection of adenosine A2A receptor agonist/antagonist induced ipsilateral/contralateral-biased swing, respectively. In addition, the electrophysiological and behavioral findings also revealed that activation of dopamine D2 receptors by quinpirole strengthened KW6002/SCH442416-induced excitation of pallidal activity. Co-application of quinpirole with KW6002 or SCH442416 alleviated biased swing in hemi-parkinsonian rats. Based on the present findings, we concluded that pallidal adenosine A2A receptors may be potentially useful in the treatment of Parkinson's disease.
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Affiliation(s)
- Hui-Ling Diao
- Department of Physiology, Qingdao University, Qingdao, China.,Department of Physiology, Binzhou Medical University, Yantai, China
| | - Yan Xue
- Department of Physiology, Qingdao University, Qingdao, China
| | - Xiao-Hua Han
- Department of Physiology, Qingdao University, Qingdao, China
| | - Shuang-Yan Wang
- Department of Physiology, Qingdao University, Qingdao, China.,Department of Anatomy, Qingdao University, Qingdao, China
| | - Cui Liu
- Department of Physiology, Qingdao University, Qingdao, China
| | - Wen-Fang Chen
- Department of Physiology, Qingdao University, Qingdao, China
| | - Lei Chen
- Department of Physiology, Qingdao University, Qingdao, China
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Morales-Figueroa GE, Márquez-Gómez R, González-Pantoja R, Escamilla-Sánchez J, Arias-Montaño JA. Histamine H3 receptor activation counteracts adenosine A2A receptor-mediated enhancement of depolarization-evoked [3H]-GABA release from rat globus pallidus synaptosomes. ACS Chem Neurosci 2014; 5:637-45. [PMID: 24884070 DOI: 10.1021/cn500001m] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
High levels of histamine H3 receptors (H3Rs) are found in the globus pallidus (GP), a neuronal nucleus in the basal ganglia involved in the control of motor behavior. By using rat GP isolated nerve terminals (synaptosomes), we studied whether H3R activation modified the previously reported enhancing action of adenosine A2A receptor (A2AR) stimulation on depolarization-evoked [(3)H]-GABA release. At 3 and 10 nM, the A2AR agonist CGS-21680 enhanced [(3)H]-GABA release induced by high K(+) (20 mM) and the effect of 3 nM CGS-21680 was prevented by the A2AR antagonist ZM-241385 (100 nM). The presence of presynaptic H3Rs was confirmed by the specific binding of N-α-[methyl-(3)H]-histamine to membranes from GP synaptosomes (maximum binding, Bmax, 1327 ± 79 fmol/mg protein; dissociation constant, Kd, 0.74 nM), which was inhibited by the H3R ligands immepip, clobenpropit, and A-331440 (inhibition constants, Ki, 0.28, 8.53, and 316 nM, respectively). Perfusion of synaptosomes with the H3R agonist immepip (100 nM) had no effect on K(+)-evoked [(3)H]-GABA release, but inhibited the stimulatory action of A2AR activation. In turn, the effect of immepip was blocked by the H3R antagonist clobenpropit, which had no significant effect of its own on K(+)-induced [(3)H]-GABA release. These data indicate that H3R activation selectively counteracts the facilitatory action of A2AR stimulation on GABA release from striato-pallidal projections.
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Affiliation(s)
- Guadalupe-Elide Morales-Figueroa
- Departamento de Fisiología,
Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico
Nacional 2508, Zacatenco, 07360 México, D.F., México
| | - Ricardo Márquez-Gómez
- Departamento de Fisiología,
Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico
Nacional 2508, Zacatenco, 07360 México, D.F., México
| | - Raúl González-Pantoja
- Departamento de Fisiología,
Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico
Nacional 2508, Zacatenco, 07360 México, D.F., México
| | - Juan Escamilla-Sánchez
- Departamento de Fisiología,
Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico
Nacional 2508, Zacatenco, 07360 México, D.F., México
| | - José-Antonio Arias-Montaño
- Departamento de Fisiología,
Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico
Nacional 2508, Zacatenco, 07360 México, D.F., México
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L-type Ca2+ channel activity determines modulation of GABA release by dopamine in the substantia nigra reticulata and the globus pallidus of the rat. Neuroscience 2014; 256:292-301. [DOI: 10.1016/j.neuroscience.2013.10.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Osorio-Espinoza A, Alatorre A, Ramos-Jiménez J, Garduño-Torres B, García-Ramírez M, Querejeta E, Arias-Montaño JA. Pre-synaptic histamine H₃ receptors modulate glutamatergic transmission in rat globus pallidus. Neuroscience 2010; 176:20-31. [PMID: 21195747 DOI: 10.1016/j.neuroscience.2010.12.051] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 12/22/2010] [Accepted: 12/24/2010] [Indexed: 02/04/2023]
Abstract
The globus pallidus, a neuronal nucleus involved in the control of motor behavior, expresses high levels of histamine H(3) receptors (H(3)Rs) most likely located on the synaptic afferents to the nucleus. In this work we studied the effect of the activation of rat pallidal H(3)Rs on depolarization-evoked neurotransmitter release from slices, neuronal firing rate in vivo and turning behavior. Perfusion of globus pallidus slices with the selective H(3)R agonist immepip had no effect on the release of [(3)H]-GABA ([(3)H]-γ-aminobutyric acid) or [(3)H]-dopamine evoked by depolarization with high (20 mM) K(+), but significantly reduced [(3)H]-d-aspartate release (-44.8 ± 2.6% and -63.7 ± 6.2% at 30 and 100 nM, respectively). The effect of 30 nM immepip was blocked by 10 μM of the selective H(3)R antagonist A-331440 (4'-[3-[(3(R)-dimethylamino-1-pyrrolidinyl]propoxy]-[1,1-biphenyl]-4'-carbonitrile). Intra-pallidal injection of immepip (0.1 μl, 100 μM) decreased spontaneous neuronal firing rate in anaesthetized rats (peak inhibition 68.8±10.3%), and this effect was reversed in a partial and transitory manner by A-331440 (0.1 μl, 1 mM). In free-moving rats the infusion of immepip (0.5 μl; 10, 50 and 100 μM) into the globus pallidus induced dose-related ipsilateral turning following systemic apomorphine (0.5 mg/kg, s.c.). Turning behavior induced by immepip (0.5 μl, 50 μM) and apomorphine was partially prevented by the local injection of A-331440 (0.5 μl, 1 mM) and was not additive to the turning evoked by the intra-pallidal injection of antagonists at ionotropic glutamate receptors (0.5 μl, 1 mM each of AP-5, dl-2-amino-5-phosphonovaleric acid, and CNQX, 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione). These results indicate that pre-synaptic H(3)Rs modulate glutamatergic transmission in rat globus pallidus and thus participate in the control of movement by basal ganglia.
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Affiliation(s)
- A Osorio-Espinoza
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. Instituto Politécnico Nacional 2508, Zacatenco, 07360 México, D.F., México
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11
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Azdad K, Gall D, Woods AS, Ledent C, Ferrié S, Schiffmann SN. Dopamine D2 and adenosine A2A receptors regulate NMDA-mediated excitation in accumbens neurons through A2A-D2 receptor heteromerization. Neuropsychopharmacology 2009; 34:972-86. [PMID: 18800071 PMCID: PMC5527972 DOI: 10.1038/npp.2008.144] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Bursting activity of striatal medium spiny neurons results from membrane potential oscillations between a down- and an upstate that could be regulated by G-protein-coupled receptors. Among these, dopamine D(2) and adenosine A(2A) receptors are highly enriched in striatal neurons and exhibit strong interactions whose physiological significance and molecular mechanisms remain partially unclear. More particularly, respective involvements of common intracellular signaling cascades and A(2A)-D(2) receptor heteromerization remain unknown. Here we show, by performing perforated-patch-clamp recordings on brain slices and loading competitive peptides, that D(2) and A(2A) receptors regulate the induction by N-methyl-D-aspartate of a depolarized membrane potential plateau through mechanisms relying upon specific protein-protein interactions. Indeed, D(2) receptor activation abolished transitions between a hyperpolarized resting potential and a depolarized plateau potential by regulating the Ca(V)1.3a calcium channel activity through interactions with scaffold proteins Shank1/3. Noticeably, A(2A) receptor activation had no effect per se but fully reversed the effects of D(2) receptor activation through a mechanism in which A(2A)-D(2) receptors heteromerization is strictly mandatory, demonstrating therefore a first direct physiological relevance of these heteromers. Our results show that membrane potential transitions and firing patterns in striatal neurons are tightly controlled by D(2) and A(2A) receptors through specific protein-protein interactions including A(2A)-D(2) receptors heteromerization.
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Affiliation(s)
- Karima Azdad
- Laboratory of Neurophysiology, Université Libre de Bruxelles, Brussels, Belgium.
| | - David Gall
- Laboratory of Neurophysiology, Université Libre de Bruxelles, Brussels, Belgium,European Graduate School of Neuroscience (EURON), Brussels, Belgium
| | - Amina S Woods
- Intramural Research Program, Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, MD, USA
| | | | - Sergi Ferrié
- Intramural Research Program, Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, MD, USA
| | - Serge N Schiffmann
- Laboratory of Neurophysiology, Université Libre de Bruxelles, Brussels, Belgium,European Graduate School of Neuroscience (EURON), Brussels, Belgium,Correspondence: Dr K Azdad or Professor SN Schiffmann, Laboratoire de Neurophysiologie, Université Libre de Bruxelles CP601, Campus Erasme, route de Lennik 808, 1070 Brussels, Belgium, Tel: +3225554103, Fax: +3225554121, ,
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12
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Gonzalez B, Paz F, Florán L, Aceves J, Erlij D, Florán B. Cannabinoid agonists stimulate [3H]GABA release in the globus pallidus of the rat when G(i) protein-receptor coupling is restricted: role of dopamine D2 receptors. J Pharmacol Exp Ther 2008; 328:822-8. [PMID: 19106171 DOI: 10.1124/jpet.108.145425] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The motor effects of cannabinoids in the globus pallidus appear to be caused by increases in interstitial GABA. To elucidate the mechanism of this response, we investigated the effect of the selective cannabinoid type 1 receptor (CB1) cannabinoid agonist arachidonyl-2-chloroethylamide (ACEA) on [(3)H]GABA release in slices of the rat globus pallidus. ACEA had two effects: concentrations between 10(-8) and 10(-6) M stimulated release, whereas higher concentrations (IC(50) approximately 10(-6) M) inhibited it. Another cannabinoid agonist, WIN-55,212-2, also had bimodal effects on release. Studies of cAMP production indicate that under conditions of low G(i/o), availability the coupling of CB1 receptors with G(i/o) proteins can be changed into CB1:G(s/olf) coupling; therefore, we determined the effects of conditions that limit G(i/o) availability on [(3)H]GABA release. Blockers of G(i/o) protein interactions, pertussis toxin and N-ethylmaleimide, transformed the inhibitory effects of ACEA on GABA release into stimulation. It also has been suggested that stimulation of D2 receptors can reduce G(i/o) availability. Blocking D2 receptors with sulpiride [(S)-5-aminosulfonyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-methoxybenzamidersqb] or depleting dopamine with reserpine inhibited the ACEA-induced stimulation of release. Thus, the D2 dependence of stimulation is consistent with the proposal that D2 receptors reduce G(i/o) proteins available for binding to the CB1 receptor. In summary, CB1 receptor activation has dual effects on GABA release in the globus pallidus. Low concentrations stimulate release through a process that depends on activation of dopamine D2 receptors that may limit G(i/o) protein availability. Higher concentrations of cannabinoid inhibit GABA release through mechanisms that are independent of D2 receptor activation.
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Affiliation(s)
- Brenda Gonzalez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del InstitutoPolitécnico Nacional, Mexico
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13
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A Role for Adenosine A1 Receptors in GABA and NMDA-Receptor Mediated Modulation of Dopamine Release: Studies Using Fast Cyclic Voltammetry. SENSORS 2008; 8:5516-5534. [PMID: 27873828 PMCID: PMC3705518 DOI: 10.3390/s8095516] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Revised: 09/01/2008] [Accepted: 09/02/2008] [Indexed: 11/17/2022]
Abstract
In the striatum many neurotransmitters including GABA, glutamate, acetylcholine, dopamine, nitric oxide and adenosine interact to regulate synaptic transmission. Dopamine release in the striatum is regulated by a number of pre- and post-synaptic receptors including adenosine. We have recently shown using isolated rat striatal slices, and the technique of fast cyclic voltammetry, that adenosine A1 receptor-mediated inhibition of dopamine release is modulated by dopamine D1 receptors. In the present study we have investigated the influence of NMDA and GABA receptor activation on the modulation of electrically stimulated dopamine release by adenosine. Application of the adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA), concentration-dependently inhibited dopamine release to a maxiumum of 50%. Perfusion of the glutamate receptor agonist, NMDA, in low magnesium, caused a rapid and concentration-dependent inhibition of dopamine release. Prior perfusion with the adenosine A1 receptor antagonist, DPCPX, significantly reduced the effect of 5 μM and 10 μM NMDA on dopamine release. The GABAA receptor agonist, isoguvacine, had a significant concentration-dependent inhibitory effect on dopamine release which was reversed by prior application of the GABAA receptor antagonist, picrotoxin, but not DPCPX. Finally inhibition of dopamine release by CPA (1μM) was significantly enhanced by prior perfusion with picrotoxin. These data demonstrate an important role for GABA, NMDA and adenosine in the modulation of dopamine release.
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Mihara T, Iwashita A, Matsuoka N. A novel adenosine A(1) and A(2A) receptor antagonist ASP5854 ameliorates motor impairment in MPTP-treated marmosets: comparison with existing anti-Parkinson's disease drugs. Behav Brain Res 2008; 194:152-61. [PMID: 18657577 DOI: 10.1016/j.bbr.2008.06.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 06/26/2008] [Accepted: 06/29/2008] [Indexed: 11/17/2022]
Abstract
Recent evidence indicates that adenosine A(2A) receptor antagonists hold therapeutic potential for the treatment of Parkinson's disease (PD). A study on the novel adenosine A(1) and A(2A) receptor dual antagonist 5-[5-amino-3-(4-fluorophenyl)pyrazin-2-yl]-1-isopropylpyridine-2(1H)-one (ASP5854) showed it to be effective in various rodents models of PD and cognition. In the present study, we further investigated the potential of ASP5854 as an anti-PD drug using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated common marmosets, which is a highly predictive model of clinical efficacy in PD, and compared its effect with those of existing anti-PD drugs. ASP5854 significantly and dose-dependently improved the total motor disability score for 7h at doses higher than 1mg/kg, and significantly increased total locomotor activity at doses higher than 0.1mg/kg without adverse effects. l-3,4-Dihydroxyphenylalanine+benserazide and bromocriptine also significantly improved the motor disability score and the hypolocomotion caused by MPTP treatment in a dose-dependent fashion. This amelioration was significant at 32+8 and 10-32 mg/kg, respectively, although bromocriptine induced severe emesis. Trihexiphenidyl also significantly improved the total motor disability score at doses of 10-32 mg/kg; however, while a significant increase in the total locomotor activity was observed at 10mg/kg, the drug induced ataxia-like behavior at 32 mg/kg. On the other hand, neither selegiline nor amantadine improved the total motor disability and hypolocomotion. These data substantiate the evidence that the novel adenosine antagonist ASP5854 exerts comparable anti-PD activity with existing anti-PD drugs, which indicates that ASP5854 might have potential to ameliorate motor deficits in PD.
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Affiliation(s)
- Takuma Mihara
- Department of Neuroscience, Pharmacology Research Labs, Astellas Pharma Inc., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan.
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Rose S, Ramsay Croft N, Jenner P. The novel adenosine A2a antagonist ST1535 potentiates the effects of a threshold dose of l-dopa in unilaterally 6-OHDA-lesioned rats. Brain Res 2007; 1133:110-4. [PMID: 17196564 DOI: 10.1016/j.brainres.2006.10.038] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 10/05/2006] [Accepted: 10/21/2006] [Indexed: 11/21/2022]
Abstract
Adenosine A2a antagonists can modulate dopamine-mediated motor behaviours, however, their ability to induce rotational behaviour in 6-hydroxydopamine (6-OHDA)-lesioned rats and to potentiate the effects of l-dopa differs. We now report on the effects of the novel A2a antagonist ST1535 on rotational responses in this model. When administered alone, ST1535 (2.5-40 mg/kg po) enhanced exploratory behaviour and produced a dose-related increase in ipsilateral rotation in rats with a unilateral 6-OHDA lesion of the nigro-striatal pathway. Administration of ST1535 (40 mg/kg po) in combination with a high dose of l-dopa (12 mg/kg ip) caused marked contraversive rotation but did not alter the rotational response produced by l-dopa alone. In contrast, when administered in combination with l-dopa (7 mg/kg ip) that alone produced a submaximal circling response, ST1535 enhanced the intensity and duration of rotation. These results suggest that ST1535 is able to alter dopamine-mediated behaviour when given alone and to potentiate the effects of submaximal doses of l-dopa. ST1535 may be useful in the treatment of Parkinson's disease and effective in reducing the use of l-dopa.
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Affiliation(s)
- Sarah Rose
- Neurodegenerative Disease Research Centre, School of Health and Biomedical Sciences, Kings College, London SE1 1UL, UK
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Abstract
The external segment of the pallidum (GP(e)) is a relatively large nucleus located caudomedial to the neostriatum (Str). The GP(e) receives major inputs from two major basal ganglia input nuclei, the Str and the subthalamic nucleus (STN), and sends its output to many basal ganglia nuclei including the STN, the Str, the internal pallidal segment (GP(i)), and the substantia nigra (SN). Thus, the GPe can be placed at the center of the basal ganglia connection diagram (Fig. 1(A)). From the viewpoint that emphasizes the direct and indirect pathways of the basal ganglia, the GP(e) is a component of the indirect pathway that relays Str inputs to the STN. The indirect pathway can be traced in Fig. 1(A), although it comprises only a part of multiple indirect pathways. This chapter begins with a brief description of the anatomical organization of the GP(e) followed by physiological and pharmacological characterizations of GABAergic responses in the GP(e).
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Affiliation(s)
- Hitoshi Kita
- Department of Anatomy and Neurobiology, The University of Tennessee Memphis, 855 Monroe Avenue, Memphis, TN 38163, USA.
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17
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Misgeld U, Drew G, Yanovsky Y. Presynaptic modulation of GABA release in the basal ganglia. PROGRESS IN BRAIN RESEARCH 2007; 160:245-59. [PMID: 17499118 DOI: 10.1016/s0079-6123(06)60014-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Presynaptic receptors provide plasticity to GABAergic synapses in the basal ganglia network, in which GABA neurons outnumber all other neurons. Presynaptic receptors, mostly of the metabotropic type, enhance or reduce the strength of synaptic inhibition and are activated by ligands being released from the GABA terminals themselves (autoreceptors) or by ligands coming from other sources (heteroreceptors), including the target neurons innervated by the GABA terminals. The latter mechanism, termed retrograde signaling, is given particular emphasis as far as it occurs in substantia nigra.
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Affiliation(s)
- Ulrich Misgeld
- Institute of Physiology and Pathophysiology and Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, Im Neuenheimer Feld 326, D-69120 Heidelberg, Germany.
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Rose S, Jackson MJ, Smith LA, Stockwell K, Johnson L, Carminati P, Jenner P. The novel adenosine A2a receptor antagonist ST1535 potentiates the effects of a threshold dose of l-DOPA in MPTP treated common marmosets. Eur J Pharmacol 2006; 546:82-7. [PMID: 16925991 DOI: 10.1016/j.ejphar.2006.07.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 06/22/2006] [Accepted: 07/14/2006] [Indexed: 12/01/2022]
Abstract
Adenosine A(2a) receptor antagonists may represent a novel non-dopaminergic approach to the treatment of Parkinson's disease. However, there is little information available on their ability to reverse motor deficits in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine hydrochloride (MPTP)-treated primates. We have studied the effects of the novel A(2a) receptor antagonist 2-butyl-9-methyl-8-(2H-1,2,3-triazol 2-yl)-9 H-purin-6-ylamine (ST1535) alone and in combination with l-3, 4-dihydroxyphenylalanine (L-DOPA) in MPTP-treated common marmosets. ST1535 (10, 20 and 40 mg/kg, p.o.) when administered alone to MPTP-treated common marmosets produced a dose related increase in locomotor motor activity and tended to reverse motor disability. Treatment with a threshold dose of L-DOPA (2.5 mg/kg, p.o.) produced an increase in locomotor activity and again tended to reverse motor disability. When L-DOPA (2.5 mg/kg, p.o.) was administered in combination with ST1535 (20 mg/kg, p.o.), there was an enhancement in the intensity and duration of the effect of L-DOPA (2.5 mg/kg, p.o.) in reversing motor deficits as shown by both a further increase in locomotor activity and reversal of motor disability. The combination of L-DOPA (2.5 mg/kg, p.o.) plus ST1535 (20 mg/kg, p.o.) significantly increased "on time" in these animals. These data substantiate the evidence that adenosine A(2a) receptor antagonists are able to reverse motor deficits in a highly predictive model of clinical efficacy in Parkinson's disease. The data suggests that ST1535 will be an effective anti-parkinsonian agent in combination with L-DOPA and allow a reduction in l-DOPA usage in the treatment of Parkinson's disease.
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Affiliation(s)
- Sarah Rose
- Neurodegenerative Disease Research Centre, School of Health and Biomedical Sciences, King's College, London SE1 1UL UK
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Shakirzyanova AV, Bukharaeva EA, Nikolsky EE, Giniatullin RA. Negative cross-talk between presynaptic adenosine and acetylcholine receptors. Eur J Neurosci 2006; 24:105-15. [PMID: 16800865 DOI: 10.1111/j.1460-9568.2006.04884.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Functional interactions between presynaptic adenosine and acetylcholine (ACh) autoreceptors were studied at the frog neuromuscular junction by recording miniature end-plate potentials (MEPPs) during bath or local application of agonists. The frequency of MEPPs was reduced by adenosine acting on presynaptic adenosine A1 receptors (EC(50) = 1.1 microm) or by carbachol acting on muscarinic M2 receptors (EC(50) = 1.8 microm). However, carbachol did not produce the depressant effect when it was applied after the action of adenosine had reached its maximum. This phenomenon implied that the negative cross-talk (occlusion) had occurred between A1 and M2 receptors. Moreover, the occlusion was receptor-specific as ATP applied in the presence of adenosine continued to depress MEPP frequency. Muscarinic antagonists [atropine or 1-[[2-[(diethylamino)methyl)-1-piperidinyl]acetyl]-5,11-dihydro-6H-pyrido [2,3-b][1,4]benzodiazepine-6-one) (AFDX-116)] had no effect on the inhibitory action of adenosine and adenosine antagonists [8-(p-sulfophenyl)theophylline (8-SPT) or 1,3-dipropyl-8-cyclopentylxanthine (DPCPX)] had no effect on the action of carbachol. These data suggested that membrane-delimited interactions did not occur between A1 and M2 receptors. Both carbachol and adenosine similarly inhibited quantal release triggered by high potassium, ionomycin or sucrose. These results indicated a convergence of intracellular pathways activated by M2 and A1 receptors to a common presynaptic effector located downstream of Ca(2+) influx. We propose that the negative cross-talk between two major autoreceptors could take place during intense synaptic activity and thereby attenuate the presynaptic inhibitory effects of ACh and adenosine.
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Affiliation(s)
- A V Shakirzyanova
- Kazan Institute of Biochemistry and Biophysics KSC RAS, 420111 Kazan, Tatarstan, Russia
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Gonzalez B, Paz F, Florán L, Aceves J, Erlij D, Florán B. Adenosine A2A receptor stimulation decreases GAT-1-mediated GABA uptake in the globus pallidus of the rat. Neuropharmacology 2006; 51:154-9. [PMID: 16730753 DOI: 10.1016/j.neuropharm.2006.03.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Revised: 02/17/2006] [Accepted: 03/13/2006] [Indexed: 11/20/2022]
Abstract
We examined modulation of [(3)H]GABA uptake in slices of the rat globus pallidus because stimulation of adenosine A(2A) receptors increases extracellular GABA in this structure. Pharmacological analysis showed that GAT-1 is the main transporter present in these slices. Both adenosine and the A(2A) agonist CGS 21680 reduced GABA uptake. Antagonist ZM 241385 prevented these effects. Agents that increase protein kinase A activity like forskolin and 8-bromo-cAMP also inhibited GABA uptake. The inhibition of uptake produced by these substances and by CGS 21680 was prevented by the protein kinase A blocker H-89. The protein phosphatase blocker okadaic acid reduced uptake; this effect and the response to CGS 21680 were not additive. The effective concentrations of adenosine (EC(50)=15.2microM) are within the range measured in the interstitial fluid under some physiological conditions. Thus, inhibition of uptake may be important in increasing interstitial GABA during endogenous adenosine release.
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Affiliation(s)
- Brenda Gonzalez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, Apartado Postal 14-740, 07000 México DF, México
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Stepnova EA, Tikhonov VE, Babushkina TA, Klemenkova ZS, Yamskov IA. Unexpected reaction of chitosan with 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline. MENDELEEV COMMUNICATIONS 2006. [DOI: 10.1070/mc2006v016n05abeh002363] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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