Presynaptic calcium currents recorded from calyciform nerve terminals in the lizard ciliary ganglion.

Electron microscopic examination of ciliary ganglion from Anolis carolinensis shows large calyciform presynaptic nerve terminals ending on ganglion cells. Intracellular records were obtained from the terminals, and membrane currents were recorded with the single-electrode voltage clamp technique. After block of Na+ currents with tetrodotoxin, depolarization of the terminals produced inward currents that disappeared when extracellular Ca2+ was removed, and increased in magnitude and duration when competing outward currents were blocked by intracellular Cs+. Thus it is possible, with this preparation, to record and characterize Ca2+ currents presumably associated with neurotransmitter release.