//genesis
/*************************** MS Model, Version 6 *********************
**************************** KaS_channel.g *********************
Rebekah Evans rcolema2@gmu.edu
Tom Sheehan tsheeha2@gmu.edu thsheeha@vt.edu 703-538-8361
******************************************************************************
******************************************************************************/
/* K A-type Slow channel
* This is a tab channel created from Kv1.2 channel data in Shen 2004.
* They are using dissociated medium spiny neurons, and did not specify recording temperature, so I am assuming room temp.
* Our data matching process showed that the original model from Johanes Hjorth via Kai Du and Tom Sheehan matched closely with the
* activation (minf) curve, but the activation tau curve was almost the opposite of the data. The KaS channel does not completely
* inactivate according to the Shen data and the model they have made to match their data. Johannes accounted for this by making two
* KaS channels one that inactivated and one that didn't and adjusted their conductances accordingly. However, it will be faster to
* have just one channel that partially inactivates. This new tab channel uses Alphas and Betas obtained by matching the model curves in Shen 2004
* figure 6. m is to the power of 2 in the previous code, I have not re-checked wolf yet to see if that's what it is there.
* Note that to distinguish these updated channels from the old, the file is now called KaS_chan.g (instead of KaS_channel.g) and the
* function is called make_KaS_chan.
* *************** Rebekah Evans 02/15/10 rcolema2@gmu.edu ********************************/
/* AB: qfactor of 2 used instead of 3 in previous channel */
function make_KAs_channel
//include tabchanforms
//initial parameters for making tab channel
float Erev = -0.09
int m_power = 2
int h_power = 1
//Activation constants for alphas and betas (obtained by matching Tkatch 2000)
float mA_rate = 0.25 //units msec
float mA_vhalf = 50
float mA_slope = -20
float mB_rate = 0.05 //units msec
float mB_vhalf = -90
float mB_slope = 35
//Inactivation constants for alphas and betas
float hA_rate = 2.5 //units sec
float hA_vhalf = -95
float hA_slope = 16
float hB_rate = 2 //units sec
float hB_vhalf = 50
float hB_slope = -70
//table filling parameters
float xmin = -0.1 /* minimum voltage we will see in the simulation */
float xmax = 0.05 /* maximum voltage we will see in the simulation */
int xdivsFiner = 3000 /* the number of divisions between -0.1 and 0.05 */
int c = 0
float increment = 1000*{{xmax}-{xmin}}/{xdivsFiner}
echo "kAs: inc="{increment}"mV"
float x = -100
float m_alpha, m_beta, h_alpha, h_beta
/* make the table for the activation with a range of -100mV - +50mV
* with an entry for every 10mV
*/
str path = "KAs_channel"
create tabchannel {path}
call {path} TABCREATE X {xdivsFiner} {xmin} {xmax}
call {path} TABCREATE Y {xdivsFiner} {xmin} {xmax}
/*fills the tabchannel with values for minf, mtau, hinf and htau,
*from the files.
*/
float qfactor=2
for (c = 0; c < {xdivsFiner} + 1; c = c + 1)
float m_alpha = {sig_form {mA_rate} {mA_vhalf} {mA_slope} {x}}
float m_beta = {sig_form {mB_rate} {mB_vhalf} {mB_slope} {x}}
float h_alpha = {sig_form {hA_rate} {hA_vhalf} {hA_slope} {x}}
float h_beta = {sig_form {hB_rate} {hB_vhalf} {hB_slope} {x}}
float xa = {1/{{m_alpha}+{m_beta}}}
float xb = {{m_alpha}/{{m_alpha}+{m_beta}}}
float ya = {1/{{h_alpha}+{h_beta}}}
float yb = {{{{h_alpha}/{{h_alpha}+{h_beta}}}*0.8}+0.2}
//the *0.8+0.2 in yb is to make the channel partially inactivate.
// Tables are filled with inf and taus in order to make this channel partially inactivate.
setfield {path} X_A->table[{c}] {(xa*1e-3)/qfactor}
setfield {path} X_B->table[{c}] {xb}
setfield {path} Y_A->table[{c}] {ya/qfactor}
setfield {path} Y_B->table[{c}] {yb}
x = x + increment
end
/* Defines the powers of m and h in the Hodgkin-Huxley equation*/
setfield {path} Ek {Erev} Xpower {m_power} Ypower {h_power}
tweaktau {path} X
tweaktau {path} Y
end
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