- Koji Kawaguchi: Division of Anatomy and Developmental Neurobiology, Kobe University Graduate School of Medicine, Japan.
The fluorescent dye PKH26, which binds mainly to the cell membrane, has long stability that enables the tracing of PKH26-labeled transplanted cells in host tissue. In the present study, we examined whether this fluorescent dye works as a retrograde or anterograde tracer to label neural networks within the central nervous system of adult and postnatal day 3 (P3) mice. A small injection of the dye into the medullospinal junction resulted in the retrograde labeling of corticospinal tract (CST) neurons in layer V of the sensory-motor cortex both in the adult mice and pups. Injection of the dye into the motor cortex of the P3 pups resulted in the anterograde labeling of CST fibers at a single fiber resolution level, although a similar injection of the dye into the motor cortex of the adult mice failed to stain CST fibers anterogradely. These results suggest that, while PKH26 works as a retrograde or anterograde tracer, anterograde labeling of the adult tracts can not be expected.