Fig. 2. Quantitation of the effects of SB-3CT on RGC axon outgrowth. Camera lucida representations of the brains and optic projections of control and treated embryos were digitized and analyzed for two measures of optic projection development: the mean angle through which RGC axons turned at the mid-diencephalon (A); and the length of the optic projection (B). (A) Dose-response curve for SB-3CT effects on the mean turning angle. The inset shows a schematic of how the turning angle was measured for a control and a SB-3CT-treated brain. Briefly, a standard reference line (1) was drawn between the optic chiasm and the midbrain-hindbrain boundary. A second line (2) was drawn at a 60° angle to line 1, and the angle through which the RGC axons turn in the mid-diencephalon was measured as the angle between line 2 and a third line (3) drawn through the middle of the optic projection just after the turn. A demonstration of the turning angle at the mid-diencephalon is shown in Fig. 1A,C. (B) Dose-response curve for SB-3CT effects on the optic projection length. Error bars are s.e.m., and numbers in brackets represent the number of optic projections analyzed. (***P<0.001; one-way ANOVA, Student-Newmann Keuls post-hoc comparisons test).