Primary hippocampal neurons were cultured on PDL, PDL coated with FNx7 without HNK-1 expression (HNK-1(-)), or PDL coated with FNx7 with HNK-1 expression (HNK-1(+)). Normal goat IgG (+ normal IgG) or anti-CNTN pAb (+ CNTN Ab) was added to the culture medium at a final concentration of 30 μg/mL after 18 h of culture. Neurons were immunostained and analyzed at DIV3. Green, PDL with normal goat IgG (n = 219); light green, PDL with anti-CNTN pAb (n = 130); yellow, FNx7 HNK-1(-) with normal goat IgG (n = 139); light yellow, FNx7 HNK-1(-) with anti-CNTN pAb (n = 163); orange, FNx7 HNK-1(+) with normal goat IgG (n = 154); and light orange, FNx7 HNK-1(+) with anti-CNTN pAb (n = 166). Numbers of measured neurons were indicated in parentheses. This experiment was performed across two independent cultures, respectively, and the representative result obtained from a single culture was shown. Error bars represent SEM. ***p < 0.001; n.s., p > 0.05.