title: Regulation of quantal transmitter secretion by ATP and protein kinases at developing neuromuscular synapses.
abstract: The effects of endogenously released ATP on the maturation of developing neuromuscular synapses were investigated in Xenopus nerve-muscle co-cultures. The potentiating action of ATP (1 mM) on spontaneous acetylcholine release was inhibited by P2-purinoceptor antagonists suramin (0.3 mM) and reactive blue 2 (RB-2, 3 microM) in day 1 cultures. Bath application of suramin (10 microM) or RB-2 in day 1 cultures and prolonged treatment for 2 days dramatically decreased the amplitude of both spontaneous synaptic currents (SSCs) and evoked synaptic currents (ESCs) in the same cultures on day 3. Chronic treatment with 8-cyclopentyltheophylline (4 microM) or 6-cyano-2,3-dihydroxy-7-nitroquinoxaline (CNQX, 10 microM), P1-purinoceptor and glutamate receptor antagonists respectively, did not exert such an inhibitory effect. Chronic treatment with suramin or RB-2 for 2 days had no significant effect on the amplitude of either iontophoretic acetylcholine-induced whole-cell currents or single acetylcholine channel measurements in 3-day-old cultured myocytes. In addition, prolonged treatment for 2 days with various kinase inhibitors such as H-8 (10 microM), KN-62 (5 microM) and H-7 (10 microM) also decreased the amplitudes of both spontaneous and evoked synaptic currents in natural synapses, but not those of iontophoretic acetylcholine-induced currents. Furthermore, suramin and these protein kinase inhibitors also decreased the amplitude of spontaneous synaptic currents in manipulated synapses of 'vacated' nerve terminals. The results suggest that endogenously released ATP, acting in concert with various protein kinases, is involved in the maintenance and/or development of the quantum size of synaptic vesicles at embryonic neuromuscular synapses.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei.
authors.forename: W M
authors.initials: WM
authors.lastname: Fu
authors.forename: Y H
authors.initials: YH
authors.lastname: Chen
authors.forename: K F
authors.initials: KF
authors.lastname: Lee
authors.forename: J C
authors.initials: JC
authors.lastname: Liou
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000109:Acetylcholine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D018920:Coculture Techniques; D004625:Embryo, Nonmammalian; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects; D007700:Kinetics; D018482:Muscle, Skeletal / Q000166:cytology / Q000294:innervation / Q000502:physiology*; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism*; D011789:Quantum Theory; D013498:Suramin / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D004791:Enzyme Inhibitors; D014227:Triazines; C053907:8-cyclopentyl-1,3-dimethylxanthine; C012842:Cibacron Blue F 3GA; D013498:Suramin; C063302:KN 62; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000255:Adenosine Triphosphate; D013806:Theophylline; D011494:Protein Kinases; D000109:Acetylcholine