Developmental trends of age-dependent decrease in NKCC1 and age-dependent increase in KCC2 immunoreactivity during the first 3 postnatal weeks in the PBC (A), Amb (B), XII (C), NTSVL (D), RTN/pFRG (E), and CN (F). The highest optical densitometric (OD) value of each marker for each nucleus was set at 1 for comparison. The two trends intersected around P11 for the first five nuclei (A – E). (Modified from Liu and Wong-Riley, 2012).