Fig. 4.
Repetitive stimulation of proximal apical dendritic (A, B) and perisomatic (C, D) fields of an IB (A,C) and an RS cell (B, D) via localized release of caged glutamate. The bathing medium contained 0.2 mm Ca2+ and 4 mmMg2+ to block synaptic transmission.Inset, Schematic diagram of a pyramidal cell and relative positions of the stimulated areas. A,B, Photolysis of caged glutamate in 50 × 50 μm large fields positioned ∼150 μm away from the soma of the recorded cells and (C, D) on the apical dendrite close to the soma. Repetitive stimulation at 10 sec intervals reliably induces a membrane depolarization, which only during perisomatic stimulation triggers a burst (C) or a single action potential (D). Twenty subsequent traces are superimposed to illustrate the stability of the responses to caged glutamate photolysis. The recordings were performed at resting membrane potential of −62 mV in the IB cell and −68 mV in the RS cell.