Two endocytic recycling routes selectively fill two vesicle pools in frog motor nerve terminals

Neuron. 2000 Sep;27(3):551-9. doi: 10.1016/s0896-6273(00)00065-9.


We have identified and characterized two vesicle recycling pathways in frog motor nerve terminals. We exploited the differential staining properties of FM dyes of varying hydrophobicity to label selectively two different vesicle pools, using optical imaging and electron microscopy of photoconverted dyes. During a 1 min tetanus, a rapidly recycling route places vesicles selectively into a small readily releasable pool comprising about 20% of vesicles. After the tetanus, a much slower pathway (from which FM2-10 but not FM1-43 can be rinsed) delivers vesicles via infoldings and cisternae selectively to a reserve pool with a halftime of about 8 min. Mixing between the two pools is slow. During stimulation at 30 Hz, 10-15 s is required to mobilize and release dye from the reserve pool.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Endocytosis / physiology*
  • Fluorescence
  • Fluorescent Dyes / pharmacokinetics
  • In Vitro Techniques
  • Motor Neurons / metabolism*
  • Muscle Contraction / physiology
  • Neuromuscular Junction / metabolism*
  • Neuromuscular Junction / ultrastructure
  • Pyridinium Compounds / pharmacokinetics
  • Quaternary Ammonium Compounds / pharmacokinetics
  • Rana pipiens
  • Synaptic Vesicles / metabolism*


  • FM1 43
  • FM2 10
  • Fluorescent Dyes
  • Pyridinium Compounds
  • Quaternary Ammonium Compounds