title: Effects of cytochalasin treatment on short-term synaptic plasticity at developing neuromuscular junctions in frogs.
abstract: 1. The role of actin microfilaments in synaptic transmission was tested by monitoring spontaneous and evoked transmitter release from developing neuromuscular synapses in Xenopus nerve-muscle cultures, using whole-cell recording of synaptic currents in the absence and presence of microfilament-disrupting agents cytochalasins B and D. 2. Treatment with cytochalasins resulted in disruption of microfilament networks in the growth cone and the presynaptic nerve terminal of spinal neurons in Xenopus nerve-muscle cultures, as revealed by rhodamine-phalloidin staining. 3. The same cytochalasin treatment did not significantly affect the spontaneous or evoked synaptic currents during low-frequency stimulation at 0.05 Hz in these Xenopus cultures. Synaptic depression induced by high-frequency (5 Hz) stimulation, however, was reduced by this treatment. Paired-pulse facilitation for short interpulse intervals was also increased by the treatment. 4. These results indicate that disruption of microfilaments alters short-term changes in transmitter release induced by repetitive activity, without affecting normal synaptic transmission at low frequency. 5. Our results support the notion that actin microfilaments impose a barrier for mobilization of synaptic vesicles from the reserve pool, but do not affect the exocytosis of immediately available synaptic vesicles at the active zone.
authors.affiliation: Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
authors.forename: X H
authors.initials: XH
authors.lastname: Wang
authors.forename: J Q
authors.initials: JQ
authors.lastname: Zheng
authors.forename: M M
authors.initials: MM
authors.lastname: Poo
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D000199:Actins / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D003572:Cytochalasins / Q000494:pharmacology*; D003593:Cytoplasm / Q000187:drug effects / Q000648:ultrastructure; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009469:Neuromuscular Junction / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D013569:Synapses / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D014981:Xenopus
chemical_list: D000199:Actins; D003572:Cytochalasins; D007473:Ion Channels; D000109:Acetylcholine