Lindgren and Moore. (1989) Identification of ionic currents at
presynaptic nerve terminal of the lizard.
J. Physiol. 414: 201-222

Experimental observations of ionic currents localized in the presynaptic
terminal region were made with a focal loose-patch clamp.  In addition
to finding Hodgkin-Huxley (HH) type sodium and potassium currents an L
type calcium channel and a calcium-activated potassium channel were
identified. 

Computer simulations matching the invasion of the action potential
(figure 2) and the major current patterns (figure 1) were able to be
generated, using only the Na and K channels of HH

The NEURON implementation of this model was prepared by Michael Hines. 
Questions about details of this implementation should be addressed to
him at michael.hines@yale.edu.