Fig. 5.
Effect of activating AMPA receptors depends on concurrent activation of NMDA receptors. A: effect of activating AMPA receptors alone (silence), control pacing, activating NMDA receptors alone, and AMPA and NMDA together. gAMPA = 0.4 mS/cm2 and gNMDA = 18 mS/cm2. B: 4 membrane potential nullclines are indicated for the silent, pacing, fast pacing, and fastest pacing cases. The middle branch of the potential nullcline (black lines) is destabilizing. The silent regime results when the Ca2+ nullcline (green dashes) intersects the stable left branch although this is difficult to discern by eye. The red dashed curves indicate the trajectory of the underlying SOP, and the arrowheads give the direction. C: heat map for firing rates. White lines indicate control AMPA/NMDA ratio; the AMPA ↑ line indicates a doubling of this ratio. [A and B adapted from Ha and Kuznetsov (2013) and C is patterned after Zakharov et al. (2016).] All parameters are the same as in Ha and Kuznetsov (2013) except gERG = 2.