The Na+/K+-ATPase generically enables deterministic bursting in class I neurons by shearing the spike-onset bifurcation structure
Fig 5
Shear transformation of the saddle-node loop (SNL) unfolding induced by the Na+/K+-ATPase.
Including a Na+/K+-ATPase into the neuron model affects the fast subsystem bifurcation diagram and thereby enables bursting dynamics in the complete system. (A) and (B): Voltage traces from the models with an electroneutral (akin to [15]) and with an electrogenic Na+/K+-ATPase for different values of the applied current Iapp (0.1, 0.25, 0.5, 0.9 μA/cm2, top to bottom). Tonic spiking and bursting dynamics occur in the paradigm with pump. (C) Two-dimensional bifurcation diagram of the fast subsystem with the electroneutral pump. The generic unfolding of the SNL bifurcation (green circle) includes a bistable area between the homoclinic (HOM) and saddle-node (SN) bifurcation lines. (D) In the model with electrogenic pump, the area of bistability is sheared. This opens up the possibility for a [K+]out hysteresis loop (yellow region) for values of Iapp between the SNL (green circle) and the HOM inflection point (purple square). Imax = 1 μA/cm2 in all panels.