Fig. 5.
Neuronal domains are elicited by increasing [IP3]i but not [Ca2+]i. A, Neuronal domains elicited by intracellular infusion of inositol 1,4,5-trisphosphate are shown. Changes in the fura-2 fluorescence signal are pseudocolor coded as ΔF/F(in percent) and superimposed on background-subtracted videoframes. The arrow points to the filled cell in the first frame that was taken 2 sec (−2) before rupture of the cell membrane (frame 0). Increasing [IP3]i triggered a concentric calcium wave with a diameter of ∼80 μm. Tangential slice of a P1 rat. B, Increasing [Ca2+]i in a single cell (arrow) by depolarizing voltage steps failed to elicit intercellular calcium waves. The cell was depolarized from a holding potential of −70 mV to +10 mV by a 40 sec train consisting of 50-msec-long depolarizations delivered at 10 Hz. The neuron was also filled with 100 μm fluo-3 to visualize its basic structure (right). Coronal slice of a P3 rat.