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

(nemo-model CaBK

  ((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 CaBK)
   ;: BK-type Purkinje calcium-activated potassium current

	      (component (type gate)

			 ;; constants
			 (const CaBK_ztau = 1.0)


			 ;; rate functions

			 (CaBK_v = (v + 5))

			 (CaBK_minf = 
  		           (let ((vh -28.9)
				 (k  6.2))
			     (1.0 / (1.0 + exp (neg ((CaBK_v - vh) / k))))))

			 (CaBK_mtau =
			   (let
			       ((y0   0.000505)
				(vh1  -33.3)
				(k1   -10.0)
				(vh2  86.4)
				(k2   10.1))
			     ((1e3) * (y0 + 1 / (exp ((CaBK_v + vh1) / k1) + 
			     	      	         exp ((CaBK_v + vh2) / k2))))))

			 (CaBK_hinf = 
			   (let ((y0  0.085)
				 (vh  -32.0)
				 (k   5.8))
			     (y0 + (1 - y0) / (1 + exp ((CaBK_v - vh) / k)))))


			 (CaBK_htau = 
			    (let ((y0   0.0019)
				  (vh1  -54.2)
				  (k1   -12.9)
				  (vh2   48.5)
				  (k2    5.2))
			      ((1e3) * (y0 + 1 / (exp ((CaBK_v + vh1) / k1) + exp ((CaBK_v + vh2) / k2))))))


			 (CaBK_zinf = 
                           (let ((k 0.001))
			     (1 / (1 + (k / cai)))))

			 (CaBK_z_alpha = (CaBK_zinf / CaBK_ztau))
			 (CaBK_z_beta  = ((1 - CaBK_zinf) / CaBK_ztau))

			 (reaction
			  (CaBK_z
			   (transitions (<-> O C CaBK_z_alpha CaBK_z_beta))
                           (conserve  (1 = (O + C)))					     
			   (initial   (let ((k 0.001))
					(1 / (1 + k / ca0))))
			   (open O)   (power 2)))
			 
			 (output CaBK_z )  

			 
			 (hh-ionic-gate 
			  (CaBK  ;; ion name: exported variables will be of the form {ion}_{id}
			   (initial-m  (CaBK_minf))
			   (initial-h  (CaBK_hinf))
			   (m-power    3)
			   (h-power    1)
			   (m-inf      (CaBK_minf))
			   (m-tau      (CaBK_mtau))
			   (h-inf      (CaBK_hinf))
			   (h-tau      (CaBK_htau))))
			 
			 )
	      
	      (component (type pore)
			 (const  gbar_CaBK  = 0.007)
			 (output gbar_CaBK ))
	      
	      (component (type permeating-ion) (name k)
			 (const e_CaBK = ek)
			 (output e_CaBK ))
	      
	      ) ;; end BK current
))