Single-cell measurements of quantal secretion induced by alpha-latrotoxin from rat adrenal chromaffin cells: dependence on extracellular Ca2+

Pflugers Arch. 1996 Oct;432(6):1039-46. doi: 10.1007/s004240050232.


alpha-Latrotoxin (alpha-LT), from black widow spider venom, is a potent enhancer of the spontaneous quantal release of neurotransmitter from a variety of nerve terminals and clonal neurosecretory cells. Using electrochemical amperometry and estimation of membrane impedance by phase detection, we present evidence that alpha-LT induces exocytosis of catecholamines from rat adrenal chromaffin cells beginning as rapidly as 30 s after close application of the toxin. This release is largely dependent on adequate levels of extracellular Ca2+ ([Ca2+]o). Lowering [Ca2+]o from 2 mM to </= 10-20 microM reduces the alpha-LT-induced rise in membrane capacitance by at least sixfold, on average, and nearly abolishes alpha-LT-induced quantal amperometric events, while still permitting insertion of non-selective cation channels. Based on these experiments, we argue that the rapid onset of alpha-LT action in promoting massive quantal release from chromaffin cells is primarily due to an increase in the Ca2+ permeability of the plasma membrane through non-selective cation channels.

Publication types

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

MeSH terms

  • Adrenal Medulla / metabolism
  • Animals
  • Calcium / metabolism
  • Calcium / pharmacology*
  • Catecholamines / metabolism*
  • Cell Membrane / physiology
  • Cell Membrane Permeability
  • Chromaffin System / metabolism*
  • Cytosol / metabolism
  • Electric Conductivity
  • Electrochemistry
  • Exocytosis
  • Ion Channels / metabolism
  • Rats
  • Spider Venoms / pharmacology*


  • Catecholamines
  • Ion Channels
  • Spider Venoms
  • alpha-latrotoxin
  • Calcium