Modulation of synaptic efficacy and synaptic depression by glial cells at the frog neuromuscular junction.
The ability of perisynaptic glial cells to modulate transmitter release and synaptic depression was studied at the frog neuromuscular junction (nmj). Injection of GTPgammaS in perisynaptic Schwann cells (PSCs), glial cells at this synapse, induced a reduction in the amplitude of nerve-evoked synaptic responses but had no effect on the frequency, the amplitude, or the duration of the miniature endplate currents (MEPCs). Also, paired pulse facilitation was not affected. The reduction in transmitter release was mediated by pertussis toxin-(PTX) sensitive and insensitive G proteins. Blockade of G proteins in PSCs with GDPbetaS reduced synaptic depression induced by high frequency trains of stimuli, whereas activation of G proteins occluded it. Hence, the activation by endogenous neurotransmitters of G proteins in PSCs induced a profound depression in neurotransmitter release.
Robitaille
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R
Département de Physiologie, Centre de Recherche en Sciences Neurologiques, Université de Montréal, Canada. robitair@ere.umontreal.ca
D000818:Animals; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D007267:Injections; D009457:Neuroglia / Q000187:drug effects / Q000502:physiology*; D009469:Neuromuscular Junction / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D037342:Pertussis Toxin; D017729:Presynaptic Terminals / Q000502:physiology; D011894:Rana pipiens; D012583:Schwann Cells / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D018377:Neurotransmitter Agents; D010566:Virulence Factors, Bordetella; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D019204:GTP-Binding Proteins