TITLE calcium HVA channels for STh COMMENT High threshold calcium channel (N/L-type), Brown et al. 1993. & Fox et al. (1989). Both done at temperature 22degC. How the q10 works: There is a q10 for the rates (alpha and beta's) called Q10 and a Q10 for the maximum conductance called gmaxQ10. The q10s should have been measured at specific temperatures temp1 and temp2 (that are 10degC apart). Ideally, as Q10 is temperature dependant, we should know these two temperatures. We used to follow the more formal Arrhenius derived Q10 approach. The temperature at which this channel's kinetics were recorded is tempb (base temperature). What we then need to calculate is the desired rate scale for now working at temperature celsius (rate_k). This was given by the empirical Arrhenius equation, using the Q10, but now is using the quick Q10 approximation. Adding CaL [Ca]i dependent inactivation. This is only for the L-type component, and is called inactivation variable 'h'. ENDCOMMENT UNITS { (mM) = (milli/liter) (mV) = (millivolt) (mA) = (milliamp) FARADAY = (faraday) (coulomb) R = (k-mole) (joule/degC) } INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)} NEURON { SUFFIX HVA USEION ca READ cai,cao,eca WRITE ica RANGE gcaN, gcaL, iNCa, iLCa GLOBAL inactLtau,inactLmax,activate_Q10,Q10,gmaxQ10,rate_k,gmax_k,temp1,temp2,tempb } PARAMETER { v (mV) dt (ms) gcaL = 0.002 (mho/cm2) gcaN = 0.012 (mho/cm2) iNCa = 0.0 (mA/cm2) iLCa = 0.0 (mA/cm2) inactLtau = 1220.0 (ms) inactLmax = 5.291291201e-01 eca cai cao celsius activate_Q10 = 1 Q10 = 1.948259241e+00 gmaxQ10 = 1.948259241e+00 temp1 = 20.0 (degC) temp2 = 30.0 (degC) tempb = 22.0 (degC) } STATE { q u h } ASSIGNED { ica (mA/cm2) qinf uinf hinf qtau (ms) utau (ms) htau (ms) rate_k gmax_k } BREAKPOINT { LOCAL vghk SOLVE states METHOD cnexp vghk = ghkg(v,cai,cao,2) iNCa = gmax_k*(gcaN * u)*q*q*vghk iLCa = gmax_k*(gcaL)*q*q*h*vghk ica = iNCa + iLCa } INITIAL { LOCAL ktemp,ktempb,ktemp1,ktemp2 if (activate_Q10>0) { rate_k = Q10^((celsius-tempb)/10) gmax_k = gmaxQ10^((celsius-tempb)/10) }else{ rate_k = 1.0 gmax_k = 1.0 } settables(v) q = qinf u = uinf setCadepLinact(cai) h = hinf } DERIVATIVE states { settables(v) q' = (qinf-q)/qtau u' = (uinf-u)/utau setCadepLinact(cai) h' = (hinf-h)/htau } PROCEDURE settables(v) { :Computes rate and other constants at current v. :Call once from HOC to initialize inf at resting v. :Voltage shifts (for temp effects) of -8.25 and -14.67 added respt. TABLE qinf, qtau, uinf, utau DEPEND celsius FROM -100 TO 100 WITH 400 :"q" N/L Ca activation system qinf = 1.0/(1.0 + exp((-16.3547869 - v)/11.3)) qtau = (1.25/(cosh(-0.031 * (v + 28.8547869)))) /rate_k :"u" N inactivation system - voltage dependent. uinf = 1.0/(1.0 + exp((v + 45.3326653)/12.5)) utau = (98.0 + cosh(0.021*(24.7673347-v))) /rate_k } PROCEDURE setCadepLinact(cai) { : set Ca dependent L-type calcium channel inactivation :"h" L inactivation system - [Ca]i dependent. hinf = inactLmax+((1.0-inactLmax)/(1.0 + exp((cai-0.7)/0.15))) htau = inactLtau /rate_k } INCLUDE "ghk.inc"