Fig. 5. Northern blot analysis of expression of trkA, trkC, and of the neuronal marker genes NPY and GAP-43 in SH-SY5Y/trkC and SY5Y/trkA cells treated with NTs. A, cells were grown for 4 days in serum-free medium alone or in medium supplemented with 100 ng/ml NT-3, 100 ng/ml NGF, or 100 ng/ml NT-3 + 100 ng/ml NGF. Total RNA (15 µg) was analyzed for expression of NPY (0.8 kb), trkA (3.5 kb), and trkC (bars at left, 2.8 and 1.2 kb). B, SH-SY5Y/trkC (3:1) and SY5Y/trkA cells were grown for 4 days in serum-containing medium supplemented with increasing concentrations of NT-3 or NGF. Fifteen µg of total RNA were analyzed for expression of NPY and GAP-43. C, SH-SY5Y/trkC (3:1 and 3:2) and SY5Y/trkA cells were grown for 4 days in serum-containing medium supplemented with 100 ng/ml NT-3 or NGF. In all panels, GAPDH (1.5 kb) mRNA levels were used as a reference for the amount of loaded RNA.