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

(nemo-model CaP

  ((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 CaP)
	      ;; HH P-type Calcium current
	      
	      (component (type gate)

			 (defun ghk (v ci co)
			   (let ((F  9.6485e4)
			   	 (R  8.3145)
   			         (T  (22 + 273.19))  
                                 (Z  2)
				 (E  ((1e-3) * v)))
                             (let ((k0 ((Z * F * E) / (R * T))))
 		               (let ((k1 (exp (neg(k0))))
			             (k2 (((Z ^ 2) * (E * (F ^ 2))) / (R * T))))
                                (1e-6) * (if (abs (1 - k1) < 1e-6) 
                                          then (Z * F * (ci - (co * k1)) * (1 - k0))
                                          else (k2 * (ci - (co * k1)) / (1 - k1)))))))
			 
			 ;; rate functions
			 (CaP_inf =  
			   (let ((cv  -19)  (ck  5.5))
			     (1.0 / (1.0 + exp (neg ((v - cv) / ck))))))

			 (CaP_tau =
			  ((1e3) *
			   (if (v > -50) 
			       then (0.000191 + (0.00376 * exp (neg (((v + 41.9) / 27.8) ^ 2))))
			       else (0.00026367 + (0.1278 * exp (0.10327 * v))))))


			 (hh-ionic-gate 
			  (CaP  ;; ion name: exported variables will be of the form {ion}_{id}
			   (initial-m  (CaP_inf))
			   (m-power    1)
			   (h-power    0)
			   (m-inf      CaP_inf)
			   (m-tau      CaP_tau)))
			 
			 )

	      (component (type permeability)

			 (defun ghk (v ci co)
			   (let ((F  9.6485e4)
			   	 (R  8.3145)
   			         (T  (22 + 273.19))  
                                 (Z  2)
				 (E  ((1e-3) * v)))
                             (let ((k0 ((Z * (F * E)) / (R * T))))
 		               (let ((k1 (exp (neg(k0))))
			             (k2 (((Z ^ 2) * (E * (F ^ 2))) / (R * T))))
                                (1e-6) * (if (abs (1 - k1) < 1e-6) 
                                          then (Z * F * (ci - (co * k1)) * (1 - k0))
                                          else (k2 * (ci - (co * k1)) / (1 - k1)))))))
			 
			 (const pcabar  = 0.00005)
			 (const cao     = 2.4)
			 (pca           = (pcabar * ghk (v cai cao)))

			 (output pca ))
	      
	      (component (type permeating-ion) (name ca) )
	      
	      ) ;; end CaP current

))