TITLE BK KCA channel for nucleus accumbens model - old version! : large conductance kca channel COMMENT Equations from Shao L.R., Halvorsrud R., Borg-Graham L., Storm J.F. The role of BK-type Ca2_-dependent K+ channels in spike broadening during repetitive firing in rat hippocampal pyramidal cells J.Physiology (1999),521:135-146 The Krasnow Institute George Mason University Copyright Maciej Lazarewicz, 2001 (mlazarew@gmu.edu) All rights reserved. ENDCOMMENT NEURON { SUFFIX bkkca USEION k READ ek WRITE ik USEION ca READ cai RANGE gkbar,ik, q } UNITS { (molar) = (1/liter) (mM) = (millimolar) (S) = (siemens) (mA) = (milliamp) (mV) = (millivolt) } PARAMETER { turnOffinact = 1 (1) gkbar = 0.001 (S/cm2) q = 1 celsius (degC) } ASSIGNED { v (mV) cai (mM) ik (mA/cm2) k1 (/ms) k2 (/ms) k3 (/ms) k4 (/ms) q10 (1) ek (mV) } STATE { cst ost ist } BREAKPOINT { SOLVE kin METHOD sparse ik = gkbar * ost * ( v - ek ) } INITIAL { SOLVE kin STEADYSTATE sparse } KINETIC kin { rates(v) ~cst<->ost (k3,k4) ~ost<->ist (k1,0.0) ~ist<->cst (k2,0.0) CONSERVE cst+ost+ist=1 } PROCEDURE rates( v(mV)) { k1=alp( 0.1, v, -10.0, 1.0 ) k2=alp( 0.1, v, -120.0, -10.0 ) k3=alpha( 0.001, 1.0, v, -20.0, 7.0 ) *1.0e8* ( cai*1.0(/mM) )^3 k4=alp( 0.01, v, -44.0, -5.0 ) } FUNCTION alpha( tmin(ms), tmax(ms), v(mV), vhalf(mV), k(mV) )(/ms){ alpha = q / ( tmin + 1.0 / ( 1.0 / (tmax-tmin) + exp((v-vhalf)/k)*1.0(/ms) ) ) } FUNCTION alp( tmin(ms), v(mV), vhalf(mV), k(mV) )(/ms){ alp = q / ( tmin + exp( (v-vhalf) / k )*1.0(ms) ) }