My mistake. i_cap is a special name not derived from the mechanism names and needs to be added to the
list of such range variable names that are to be available from Python. See http://www.neuron.yale.edu/hg/neuron/nr ... 0c15acdfb5
for the one line fix assuming you are building NEURON from sources. If you need an installer, from http://www.neuron.yale.edu/ftp/neuron/versions/alpha/
let me know which you need and I'll put one there.