how to measure axial current?

[Xiaoshen]

My model is a pyramidal neuron with synapses distributed on the dendritic tree. I hope to "put" a tiny amper-meter inside a branch to measure the current flowing through this position after a distal synapase was excited. But I don't know how to do it.
Thank you very much.

[ted]

One way to measure axial current is to measure the membrane potential at two
adjacent nodes, and divide by the axial (cytoplasmic) resistance that separates them.
Example: if the dendritic section is called dend, the axial current between the 0 end of
dend and its first internal node is iax given by

Code: Select all

dend { iax = ( v(0.01) - v(0) ) / ri(0.01) }

This assumes that the 0 end of dend is attached to its parent, and that dend.nseg < 100.
iax > 0 means current flow is toward the 0 end.