Evidence for activity-dependent modulation of sensory-terminal excitability in spindles by glutamate release from synaptic-like vesicles

Robert W Banks, Guy Smith Bewick, Christine Richardson, Brian Reid

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17 Citations (Scopus)


Sensory terminals of muscle spindles and similar mechanosensory neurons contain large numbers of 50 nm, "synaptic-like" vesicles (SLVs), about whose role very little is known. Using fluorescence microscopy, immunocytochemistry and electrophysiological recording, we present evidence that SLVs undergo a recycling process, and that they release glutamate that has an autogenic excitatory effect on mechanosensory transduction, probably involving a metabotropic receptor linked to phospholipase D. The rate of recycling of SLVs is activity dependent, at least in part, as shown by an increased rate of destaining of preparations labelled with FMI-43 during high-frequency, small-amplitude vibration. Immunogold labelling showed levels of glutamate-like reactivity in the sensory terminals at least as great as in probable Ia presynaptic terminals in the spinal cord. Exogenously applied glutamate has an excitatory effect on the spindle's response to stretch, which is blocked by 3,5-dihydroxyphenylglycine.
Original languageEnglish
Pages (from-to)13-18
Number of pages6
JournalAdvances in Experimental Medicine and Biology
Publication statusPublished - 1 Jan 2002



  • Animals
  • Electrophysiology
  • Glutamic Acid
  • Immunohistochemistry
  • Microscopy, Fluorescence
  • Muscle Spindles
  • Rats
  • Sensation
  • Stress, Mechanical
  • Synaptic Vesicles

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