Preferential inhibition of omega-conotoxin-sensitive presynaptic Ca2+ channels by adenosine autoreceptors

Nature. 1993 Sep 16;365(6443):256-8. doi: 10.1038/365256a0.


Adenosine is a potent modulator of transmitter release at a variety of synapses. The adenosine A1 receptor is assumed to reside in presynaptic terminals and to function as a negative autoreceptor. How adenosine reduces transmitter release is uncertain; it may reduce the calcium influx during nerve terminal depolarization by either activating K+ currents or inhibiting Ca2+ currents, although other mechanisms have been proposed. We have directly measured intracellular Ca2+ concentrations of giant pre-synaptic terminals in the chick ciliary ganglion. We report here that adenosine inhibited the nerve-evoked Ca2+ influx in the terminal by activating A1 receptors. Reduced Ca2+ influx was due largely to inhibition of omega-conotoxin GVIA-sensitive Ca2+ channels in the presynaptic terminal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine / pharmacology*
  • Animals
  • Calcium / metabolism
  • Calcium Channels / drug effects*
  • Calcium Channels / metabolism
  • Chick Embryo
  • Ganglia / drug effects
  • Ganglia / metabolism
  • Peptides / pharmacology
  • Receptors, Purinergic / drug effects*
  • Receptors, Purinergic / metabolism
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / metabolism
  • omega-Conotoxins*


  • Calcium Channels
  • Peptides
  • Receptors, Purinergic
  • omega-Conotoxins
  • Conus magus toxin
  • Adenosine
  • Calcium