NEURON's artificial spiking cells have neither membrane capacitance nor conductance,
so it is not possible to "add channels" to them in the usual sense. For the sake of
computational efficiency, they avoid numerical integration entirely. Instead, since the
analytical solutions to their system equations are known, the future trajectory of any
cell can be computed directly from its initial condition. This computation need only be
performed when that cell receives an event. Run time is therefore proportional to the
number of events delivered, and independent of the number of cells, number of
connections, or problem time. For further information, you may want to read chapter 10
in The NEURON Book, or at least this paper
Hines, M.L. and Carnevale, N.T. Discrete event simulation in the NEURON
environment. Neurocomputing 58-60:1117-1122, 2004
which is available from
http://www.neuron.yale.edu/neuron/bib/nrnpubs.html.
That said, I should mention that many enhancements are possible beyond the three
basic classes of artificial spiking cells that are built into NEURON; Bill Lytton has
developed special classes of artificial spiking cells with more complex dynamics
for his own work, so you may wish to contact him.
--Ted