title: PTX-sensitive and -insensitive synaptic modulation at the frog neuromuscular junction.
abstract: Pharmacological manipulations were used to examine the role of G proteins in modulating synaptic transmission at the frog neuromuscular junction. Pertussis toxin (PTX, a G protein antagonist) increased end-plate potential (epp) amplitude but had no effect on the amplitude or frequency of miniature end-plate potentials. Mastoparan (a G protein agonist) decreased epp amplitude, while suramin (an antagonist) increased epp amplitude. The results suggest that PTX-sensitive G proteins tonically modulate synaptic transmission by reducing the amount of transmitter released in response to presynaptic action potentials. We also showed that endogenous ATP decreased transmitter release via P2 receptor in a PTX-insensitive manner. Thus, at least two distinct mechanisms regulate neuromuscular transmission; one is coupled to PTX-sensitive G proteins and the other is not.
authors.affiliation: Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Sugiura
authors.forename: C P
authors.initials: CP
authors.lastname: Ko
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D018377:Neurotransmitter Agents / Q000378:metabolism; D010455:Peptides; D037342:Pertussis Toxin; D011894:Rana pipiens / Q000033:anatomy & histology / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013498:Suramin / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D014227:Triazines / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*; D014862:Wasp Venoms / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D018377:Neurotransmitter Agents; D010455:Peptides; D018048:Receptors, Purinergic P2; D014227:Triazines; D010566:Virulence Factors, Bordetella; D014862:Wasp Venoms; C012842:Cibacron Blue F 3GA; D013498:Suramin; C037500:mastoparan; D000255:Adenosine Triphosphate; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins