Hyperpolarizing and Depolarizing After-potentials

When Na influx is blocked by TTX, activation of the AHP is preceded by a regenerative Ca potential and thus the sensitivity or threshold of the AHP to Ca determines the extent to which Ca contributes to cellular polarization. If for instance, the Ca threshold is very low, Ca mediated depolarizations would be followed immediately by rapid repolarization. 

However, in both CAl and CA3 cells, a significant Ca mediated depolarization appears to precede activation of efflux, and oscillatory bursting of these neurons in the presence of Ba is probably due to its 

In our hands (Assaf et ai, 1981), depolarizing as opposed to hyper-polarizing after-potentials, 15-20 msec in duration, are a conspicuous feature of action potentials recorded in granule cells with resting mem- 

---