Fig. 4.

Inhibition and summation of IP₃-evoked Ca²⁺ release with paired-flash protocols. A, Fluorescence signals in the soma of a strongly responding neuron evoked by paired photolysis flashes (both 50 msec duration) delivered at varying intervals, as indicated by the arrows. Inset plots the size of the second response relative to the first response in each pair, as a function of interflash interval. Data are mean ± 1 SEM from six neurons. B, Data from a different neuron, in which additive responses were observed with pairs of brief UV flashes (15 msec) at short intervals.