Differential release of amino acids, neuropeptides, and catecholamines from isolated nerve terminals

Neuron. 1991 Apr;6(4):517-24. doi: 10.1016/0896-6273(91)90054-4.


We have investigated transmitter release from small and large dense-core vesicles in nerve terminals isolated from guinea pig hippocampus. Small vesicles are found in clusters near the active zone, and large dense-core vesicles are located at ectopic sites. The abilities of Ca2+ channel activation and uniform elevation of Ca2+ concentration (with ionophores) to evoke secretion of representative amino acids, catecholamines, and neuropeptides were compared. For a given increase in Ca2+ concentration, ionophore was less effective than Ca2+ channel activation in releasing amino acids, but not in releasing cholecystokinin-8. Titration of the average Ca2+ concentration showed that the Ca2+ affinity for cholecystokinin-8 secretion was higher than that for amino acids. Catecholamine release showed intermediate behavior. It is concluded that neuropeptide release is triggered by small elevations in the Ca2+ concentration in the bulk cytoplasm, whereas secretion of amino acids requires higher elevations, as produced in the vicinity of Ca2+ channels.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism*
  • Animals
  • Calcium / metabolism
  • Catecholamines / metabolism*
  • Exocytosis / physiology
  • Guinea Pigs
  • Membrane Potentials
  • Nerve Endings / metabolism*
  • Neuropeptides / metabolism*
  • Norepinephrine / metabolism
  • Sincalide / metabolism
  • Synaptosomes / ultrastructure


  • Amino Acids
  • Catecholamines
  • Neuropeptides
  • Sincalide
  • Calcium
  • Norepinephrine