x1 x2 compartment x1 tau1 K1 L tau1 compartment x2 tau2 K2 L tau2 compartment k1 ppERKc k2 ppERKn k3 DUSP ppERKn compartment k ppERKn compartment k4 ppERKn k5 pRSKn compartment ppERKn pRSKn n k6 n ppERKn pRSKn n k7 cFOSp compartment k7 cFOSp k8 cFOSm compartment k9 cFOSm k10 cFOS k11 cFOS ppERKc k13 pcFOS compartment k11 cFOS ppERKc k12 pcFOS k13 pcFOS