Expression of L1 decreases during postnatal development of rat spinal cord.

L1 is a cell adhesion molecule that is highly expressed on developing axons and is associated with neurite outgrowth, guidance, and fasciculation. In this study we systematically examined L1 expression at all spinal levels across eight postnatal ages to detect regional and developmental differences. We observed striking changes in the developmental pattern of L1 expression between birth (P0) and adult ages, with intense L1-immunopositive axons prevalent throughout the funiculi at P0 compared with predominantly L1-immunonegative funicular axons in adults.