Figure 3.

Effects of a 7 min exposure to 200 nm ω-CgTX GVIA on Ca²⁺ entry after nerve stimulation. A, Sample resting fluorescence image of the nerve terminal (gray-scale bar in photoelectron counts) with the well focused region of interest defined by the white box. B, Histogram showing the distribution of pixel intensities in the presence and absence of nerve stimulation as described in Figure 1 E. C, Representative difference images before (top panel) and after (bottom panel) partial blockade of N-type Ca²⁺ channels. Pseudocolor scale bar applies to both images and is expressed as ΔF/F (%). D, Cumulative frequency distribution of pixel intensity values measured before (solid line) and after (dashed line) partial blockade of N-type Ca²⁺ channels. In six terminals examined in this manner, there were no significant differences in the distribution of pixel intensities. Scale bars, 2 μm.