Cortical projections to superficial laminae of the dorsal horn and to the ventral horn of the spinal cord in the North American opossum. Studies using the orthograde transport of WGA-HRP.

The orthograde transport of horseradish peroxidase conjugated to wheat germ agglutinin (WGA-HRP) has been used to study the distribution of corticospinal axons in adult and pouch-young opossums. As predicted from the results of degeneration and autoradiographic experiments, injections of WGA-HRP into limb areas of somatic motor-sensory cortex labeled axons in the dorsal and lateral funiculi of the cervical and upper thoracic spinal cord which could be traced to dense terminal zones in laminae III-VI. In addition, we obtained evidence for the presence of a few cortical axons in the ventral white matter and for innervation of the medial part of laminae I and II, laminae VII and VIII and lamina X. A few cortical axons are even present in lamina IX.