TITLE L-type calcium channel for A2 cell adapted from Tiger Salamander Bipolar cell
:
: Modified from Fohlmeister et al, 1990, Brain Res 510, 343-345
:

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

NEURON {
	SUFFIX A2_tsbp
	USEION ca READ cai, eca, cao WRITE ica
      USEION k READ ek WRITE ik
	RANGE gcabar , gkcabar
	RANGE c_inf , m_inf
	RANGE tau_c , tau_m
	RANGE c_exp , m_exp

}


UNITS {
	(molar) = (1/liter)
	(mM) = (millimolar)
	(mA) = (milliamp)
	(mV) = (millivolt)

}

PARAMETER {
	gcabar	= 0.002			(mho/cm2)
	gkcabar = 0.0014		(mho/cm2)
	eca						(mV)
	ek          			(mV)
	cao	= 1.8				(mM)
	cai = 0.0001 			(mM)
	dt              		(ms)
	v               		(mV)

}

STATE {
	c m 
}

INITIAL {
: The initial values were determined at a resting value of -66.3232 mV in a single-compartment
:	c = 0.0016
: at -60 mV
        c = 0.0038
	  m =0.0345
}

ASSIGNED {
	ica	(mA/cm2)
	ik    (mA/cm2)
	c_inf  m_inf
	tau_c  tau_m
	c_exp  m_exp

}

BREAKPOINT {
	SOLVE states
	ica = gcabar * c*c*c * (v - eca)
	ik = gkcabar * m*m*((cai)/(cai+0.2)) * (v - ek)

	

}

PROCEDURE states() {	: exact when v held constant
	evaluate_fct(v)
	c = c + c_exp * (c_inf - c)
	m = m + m_exp * (m_inf - m)

	VERBATIM
	return 0;
	ENDVERBATIM

}

UNITSOFF

PROCEDURE evaluate_fct(v(mV)) { LOCAL a,b,am,bm
	
:CA channel

 a = (-0.3 * (v+70)) / ((exp(-0.1*(v+70))) - 1)
 b = 10 * (exp((-1*(v + 38))/9))


	tau_c = 1 / (a + b)
	c_inf = a * tau_c

: State vars to inifinity
	c_exp = 1 - exp(-dt/tau_c)

:IKCA channel

 am = (100* (230-v)) / ((exp((230-v)/52)) - 1)
 bm = 120 * (exp((-v/95)))


	tau_m = 1 / (am + bm)
	m_inf = a * tau_m

: State vars to inifinity
	m_exp = 1 - exp(-dt/tau_m)


}

UNITSON