Fig. 3. RGC axons that cross the optic chiasm in the presence of metalloproteinase inhibitors fail to extend into the contralateral diencephalon. The optic chiasm was exposed at stage 30-31, by removing the cement gland and the mesenchyme underlying the ventral forebrain. Embryos were bathed in control media (A) or in media to which either the broad-spectrum metalloproteinase inhibitor GM6001 (5-10 µM; D), SB-3CT (25 µM; C) or the GM6001 negative control (5-10 µM; B) was added. At stage 40, RGC axons were anterogradely labelled with HRP. In GM6001 and SB-3CT, the optic projection (arrowhead) failed to enter the contralateral diencephalon. Tec, tectum. Scale bar: 50 µm.