Figure 3.

Requirement of NMDA receptor activation and effects of different time spans of bicuculline application on the induction of persistent bursting. A, Application of an NMDA receptor blocker AP-5 (100 μm) during (black bar; filled circles; n = 15 slices) or after (white bar; open circles; n = 17 slices) bicuculline application (BIC; 20 μm; gray bar). Notice that AP-5 prevents the persistence of the bursting only when applied during bicuculline application (filled circles), indicating the need for NMDA receptor activation for the induction but not for the expression of the persistent bursting activity. B, Average burst frequencies before, during, and after 15, 30, and 60 min of bicuculline application (white, gray, and black bars corresponding with open, gray, and filled circles in n = 8, 15, and 35 slices, respectively); the dotted line indicates the average frequency reached during 60 min bicuculline incubation.