turning channels off

[srahim2]

i currently have an altered version of the GHK calcium channel mod file which basically allows a constant stream of calcium into the soma from the extracellular calcium store; i wanted to know if there is any hoc code i could implement that would allow me to turn the channel off or on at will; i tried the section "Simulating Blocking Channels" in the Neuron Tutorial but nothing changes when i implement the given syntax

also, just out of curiosity, is there a pre-existing calcium channel that is not voltage dependant at all?

thank you so much

[ted]

i currently have an altered version of the GHK calcium channel mod file which basically allows a constant stream of calcium into the soma from the extracellular calcium store; i wanted to know if there is any hoc code i could implement that would allow me to turn the channel off or on at will

Read the mod file to discover the name of the mechanism's permeability or channel density
parameter. For example, the pas mechanism's specific conductance is called g in the mod
file, and the SUFFIX is pas, so the hoc level name is g_pas. To "block" the pas mechanism,
one would just type
secname g_pas = 0
at the oc> prompt, where secname is the name of the section in which you want to
block pas. To block pas in all sections,
forall g_pas = 0

also, just out of curiosity, is there a pre-existing calcium channel that is not voltage dependant at all?

The mod file you want is included with the MSWin distribution of NEURON (see
c:\nrnxx\examples\nrniv\nmodl), but if you're using UNIX / Linux / OS X you'll have to
get the gzipped tar source code. Expand that and look in
nrn-x.x/share/examples/nrniv/nmodl/

[srahim2]

thanks so much! is there a way to control WHEN the gates are blocked? when i run the simulation, the oc> prompt line disappears and i can't type anything until the entire simulation is complete; can i specify it to be blocked at certain times during the simulation run and then to unblock a few milliseconds later?

[ted]

Go to the Hot tips section of The NEURON Forum and read the thread called
How to change parameters during a simulation