: Calcium activated K channel. : From Moczydlowski and Latorre (1983) J. Gen. Physiol. 82 : Model 3. (Scheme R1 page 523) UNITS { (molar) = (1/liter) (mV) = (millivolt) (mA) = (milliamp) (mM) = (millimolar) FARADAY = (faraday) (kilocoulombs) R = (k-mole) (joule/degC) } NEURON { SUFFIX skkca USEION ca READ cai USEION k READ ek WRITE ik RANGE gkbar, ik, qfact, abar, bbar, stau GLOBAL oinf, tau } PARAMETER { stau = 1 qfact = 1 celsius_sk = 35 (degC) : 35 v (mV) gkbar=0.175 (mho/cm2) : Maximum Permeability cai (mM) ek (mV) d1 = .84 :page 527 Table II channel A d2 = 1.0 :our index 2 is the paper's subscript 4 k1 = .18 (mM) k2 = .011 (mM) abar = .48 (/ms) bbar = .28 (/ms) :page 524. our bbar is the paper's alpha } ASSIGNED { ik (mA/cm2) oinf tau (ms) } STATE { o } : fraction of open channels BREAKPOINT { SOLVE state METHOD cnexp ik = gkbar*o*(v - ek) } DERIVATIVE state { rate(v, cai) o' = (oinf - o)/(tau/qfact) } INITIAL { rate(v, cai) o = oinf : VERBATIM : printf("R = %f\n",R); : printf("F = %f\n",FARADAY); : ENDVERBATIM } : From R1 page 523. beta in the paper is the rate from closed to open : and we call it alp here. FUNCTION alp(v (mV), ca (mM)) (1/ms) { :callable from hoc alp = abar/(1 + exp1(k1,d1,v)/ca) } FUNCTION bet(v (mV), ca (mM)) (1/ms) { :callable from hoc bet = bbar/(1 + ca/exp1(k2,d2,v)) } FUNCTION exp1(k (mM), d, v (mV)) (mM) { :callable from hoc exp1 = k*exp(-2*d*FARADAY*v/R/(273.15 + celsius_sk)) } PROCEDURE rate(v (mV), ca (mM)) { :callable from hoc LOCAL a a = alp(v,ca) tau = stau/(a + bet(v, ca)) oinf = a*tau }