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### Customizing Rate Equations In Channel Builder

Posted: **Mon Jul 13, 2015 11:00 am**

by **Dmandel**

Hi,

I am attempting to model a Serotonergic Neuron of the Dorsal Raphe Nucleus.

I am using the CHANNEL BUILDER and I want to customize the K+ channel. How would I go about writing my own equations for N∞, IE

N∞ = 1 / 1 + e-(V-Vk)/k.

I also want to specify an equation for τn (tau), IE

τn = αk + βk / cosh((V-Vk2)/k2.

Thanks for the help!

### Re: Customizing Rate Equations In Channel Builder

Posted: **Mon Jul 13, 2015 11:42 am**

by **ted**

The Channel Builder limits your palette of equations to what is built into the Channel Builder. Furthermore, for HH-style gating, you must either use the alpha, beta or the inf, tau formulation--can't mix them.

That said, your formula for the steady state value of n is built into the Channel Builder, so the only problem is what to do about the time constant's voltage dependence. See

**importing data from clipboard into ChannelBuilderGateGUI**
http://www.neuron.yale.edu/phpbb/viewto ... =16&t=1291
After you have done that, try saving the ChannelBuilder to a ses file and see if the time constant data are preserved in that file.

### Re: Customizing Rate Equations In Channel Builder

Posted: **Mon Jul 13, 2015 5:29 pm**

by **Dmandel**

Thanks.

### How many points on the graph should I use?

Posted: **Tue Jul 14, 2015 9:58 am**

by **Dmandel**

I have successfully imported my x, y data but I don't understand how the KSchannel uses the data. Does it use the exact data points I import? Or does it make a calculation based on the data points?

### Re: Customizing Rate Equations In Channel Builder

Posted: **Tue Jul 14, 2015 12:43 pm**

by **ted**

Yes and yes. Think "piecewise linear approximation to a continuous function." Interpolation between breakpoints, and flat between -/+ inf and the first/last breakpoint.