Fig. 7. The expression of GSK-3ß-phosphorylated MAP1B is restricted to growing axons in rat embryos. Light micrographs of transverse sections of E12 rat embryo spinal cords. (A) Polyclonal antibody BUGS stains growing axons within the spinal cord, including commissural axons (arrows) and axons of the medial longitudinal tract (mlt), and axons within the PNS, including the axons of motor neurons (curved arrow) and primary sensory neurons (arrowheads). However, the proximal regions of these axons and their parent cell bodies are unstained. For example, the axonal staining in the dorsal root ganglia is largely restricted to the poles of the ganglion whereas the central regions of the ganglia, where proximal axons and cell bodies are located, are unstained (asterisk; compare with C). (B) Polyclonal antibody SuperBUGS has a staining pattern similar to that of pAb BUGS (A) except that the lack of staining of the proximal regions of axons is more pronounced. For example there is an unstained gap between the spinal cord and the proximal staining of axons in the ventral roots (arrowheads with asterisks). SuperBUGS also stains the spindle apparatus of mitotic cells scattered throughout the embryo but in particularly high numbers in the ventricular zone (arrowheads) near the central canal (cc). The inset shows a high power view of the staining of mitotic cells. (C) Polyclonal antibody MAP1B N-19 recognises all forms of MAP1B. Neurons are stained throughout their entirety including cell bodies and axons. Neuronal cell bodies in the dorsal root ganglia (asterisk) and the ventral motor neuron pool (mn) are particularly prominent. (D) Polyclonal antibody to GSK-3ß stains neurons entirely including cell bodies and axons. Neuronal cell bodies in the dorsal root ganglia (asterisk) and the ventral motor neuron pool (mn) are particularly prominent. Bar, 100 µm.