title: Autoinhibition of transmitter release from PC12 cells and sympathetic neurons through a P2Y receptor-mediated inhibition of voltage-gated Ca2+ channels.
abstract: Although feedback inhibition of noradrenaline release by coreleased nucleotides is a well known phenomenon, it remained unclear which P2 receptor subtypes and associated signalling cascades may be involved. In the rat pheochromocytoma cell line PC12, 2-methylthio-ADP reduced noradrenaline release triggered by K+ depolarization more potently than ADP and ATP, whereas UDP or UTP failed to do so. The inhibition by ADP was abolished by pertussis toxin and antagonized by reactive blue 2, 2-methylthio-AMP, and AR-C69931MX, but not by suramin. AR-C69931MX acted as a competitive antagonist with an apparent affinity of 2 nm, but did not alter noradrenaline release, when PC12 cells were continuously superfused. However, when the superfusion was halted during K+ depolarization, release was significantly reduced and this inhibition was attenuated by AR-C69931MX, thus revealing ongoing autoinhibition. Rises in cellular cyclic AMP did not alter depolarization-evoked release nor its reduction by ADP, even though the nucleotide did inhibit cyclic AMP accumulation. ADP and the direct Ca2+ channel blocker Cd2+ inhibited voltage-activated Ca2+ currents, but not ATP-induced currents, and both agents reduced K+-evoked, but not ATP-evoked, release. Hence, if voltage-gated Ca2+ channels do not contribute to stimulation-evoked release, ADP fails to exert its inhibitory action. In primary cultures of rat sympathetic neurons, ADP also reduced Ca2+ currents and K+-evoked noradrenaline release, and AR-C69931MX acted again as competitive antagonist with an apparent affinity of 3 nm. These results show that P2Y12 receptors mediate an autoinhibition of transmitter release from PC12 cells and sympathetic neurons through an inhibition of voltage-gated Ca2+ channels.
authors.affiliation: Institute of Pharmacology, Medical University of Vienna, Waehringerstrasse 13a, A-1090 Vienna, Austria.
authors.forename: Stefan G
authors.initials: SG
authors.lastname: Lechner
authors.forename: Mario M
authors.initials: MM
authors.lastname: Dorostkar
authors.forename: Martina
authors.initials: M
authors.lastname: Mayer
authors.forename: Hannah
authors.initials: H
authors.lastname: Edelbauer
authors.forename: Halyna
authors.initials: H
authors.lastname: Pankevych
authors.forename: Stefan
authors.initials: S
authors.lastname: Boehm
mesh_terms: D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives*; D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002104:Cadmium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000166:cytology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D016716:PC12 Cells / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D037342:Pertussis Toxin / Q000494:pharmacology; D010627:Phenethylamines; D011188:Potassium / Q000378:metabolism; D011685:Purine Nucleotides / Q000494:pharmacology; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058925:Receptors, Purinergic P2Y12; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013498:Suramin / Q000494:pharmacology; D013872:Thionucleosides / Q000494:pharmacology; D014316:Tritium / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; C553058:P2ry12 protein, rat; D010627:Phenethylamines; D011685:Purine Nucleotides; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058925:Receptors, Purinergic P2Y12; D013872:Thionucleosides; D002104:Cadmium; D014316:Tritium; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D005576:Colforsin; D012368:4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone; D000249:Adenosine Monophosphate; D011732:Pyridoxal Phosphate; D013498:Suramin; C117446:cangrelor; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000241:Adenosine; D011188:Potassium; D009638:Norepinephrine