;; Cerebellar Purkinje Cell: resurgent Na current and high frequency
;; firing (Khaliq et al 2003).

(nemo-model Narsg

  ((input v 
	  (cai from ion-pools)
	  (ica from ion-currents))

   (const ena = 60)
   (const ek = -88)
   (const ca0 = 1e-4)

   (component (type gate-complex) (name Narsg) 

	      ;; constants
		     
	      (component (type gate)
				
			 (const Na_Con   = 0.005)
			 (const Na_Coff  = 0.5)
			 (const Na_Oon   = 0.75)
			 (const Na_Ooff  = 0.005)


			 (const Na_alfac = (pow ((Na_Oon / Na_Con) (1.0 / 4.0))))
			 (const Na_btfac = (pow ((Na_Ooff / Na_Coff) (1.0 / 4.0))))
			 
			 (const Na_alpha = 150)
			 (const Na_beta  = 3)
			 (const Na_gamma = 150)
			 (const Na_delta = 40)
			 (const Na_epsilon = 1.75)
			 (const Na_zeta = 0.03)
			 (const Na_x1 = 20)
			 (const Na_x2 = -20)
			 (const Na_x3 = 1e12)
			 (const Na_x4 = -1e12.0)
			 (const Na_x5 = 1e12.0)
			 (const Na_x6 = -25)
   
			 ;; rate functions
			 
			 (f01 = (4.0 * Na_alpha * exp (v / Na_x1)))
			 (f02 = (3.0 * Na_alpha * exp (v / Na_x1)))
			 (f03 = (2.0 * Na_alpha * exp (v / Na_x1)))
			 (f04 = (Na_alpha * exp (v / Na_x1)))
			 (f0O = (Na_gamma * exp (v / Na_x3)))
			 (fip = (Na_epsilon * exp (v / Na_x5)))
			 (f11 = (4.0 * Na_alpha * Na_alfac * exp (v / Na_x1)))
			 (f12 = (3.0 * Na_alpha * Na_alfac * exp (v / Na_x1)))
			 (f13 = (2.0 * Na_alpha * Na_alfac * exp (v / Na_x1)))
			 (f14 = (Na_alpha * Na_alfac * exp (v / Na_x1)))
			 (f1n = (Na_gamma * exp (v / Na_x3)))
			 
			 (fi1 = (Na_Con))
			 (fi2 = (Na_Con * Na_alfac))
			 (fi3 = (Na_Con * Na_alfac * Na_alfac))
			 (fi4 = (Na_Con * Na_alfac * Na_alfac * Na_alfac))
			 (fi5 = (Na_Con * Na_alfac * Na_alfac * Na_alfac * Na_alfac))
			 (fin = (Na_Oon))
			 
			 (b01 = (Na_beta * exp (v / Na_x2)))
			 (b02 = (2.0 * Na_beta * exp (v / Na_x2)))
			 (b03 = (3.0 * Na_beta * exp (v / Na_x2)))
			 (b04 = (4.0 * Na_beta * exp (v / Na_x2)))
			 (b0O = (Na_delta * exp (v / Na_x4)))
			 (bip = (Na_zeta * exp (v / Na_x6)))
			 
			 (b11 = (Na_beta * Na_btfac * exp (v / Na_x2)))
			 (b12 = (2.0 * Na_beta * Na_btfac * exp (v / Na_x2)))
			 (b13 = (3.0 * Na_beta * Na_btfac * exp (v / Na_x2)))
			 (b14 = (4.0 * Na_beta * Na_btfac * exp (v / Na_x2)))
			 (b1n = (Na_delta * exp (v / Na_x4)))
			 
			 (bi1 = (Na_Coff))
			 (bi2 = (Na_Coff * Na_btfac))
			 (bi3 = (Na_Coff * Na_btfac * Na_btfac))
			 (bi4 = (Na_Coff * Na_btfac * Na_btfac * Na_btfac))
			 (bi5 = (Na_Coff * Na_btfac * Na_btfac * Na_btfac * Na_btfac))
			 (bin = (Na_Ooff))
			 
		(reaction
		    (Na_z
		     (transitions
		      (<-> C1 C2 f01 b01)
		      (<-> C2 C3 f02 b02)
		      (<-> C3 C4 f03 b03)
		      (<-> C4 C5 f04 b04)
		      (<-> C5 O  f0O b0O)
		      (<-> O  B  fip bip)
		      (<-> O  I6 fin bin)
		      (<-> I1 I2 f11 b11)
		      (<-> I2 I3 f12 b12)
		      (<-> I3 I4 f13 b13)
		      (<-> I4 I5 f14 b14)
		      (<-> I5 I6 f1n b1n)
		      (<-> C1 I1 fi1 bi1)
		      (<-> C2 I2 fi2 bi2)
		      (<-> C3 I3 fi3 bi3)
		      (<-> C4 I4 fi4 bi4)
		      (<-> C5 I5 fi5 bi5))

		      (conserve (1 = (C1 + C2 + C3 + C4 + C5 + O + B + I1 + I2 + I3 + I4 + I5 + I6)))
		     
		     (open O)   (power 1)))
		   
		   (output Na_z )  
		   
		   )
			
		(component (type pore)
			   (const  gbar  = 0.015)
			   (output gbar ))
		
		(component (type permeating-ion) (name na)
			   (const e = ena)
			   (output e ))
		
		) ;; end Narsg component

))