Cutaneous projections from the rat hindlimb foot to the substantia gelatinosa of the spinal cord studied by transganglionic transport of WGA-HRP conjugate.

The somatotopic organization of cutaneous afferent fibers from the hindlimb foot in the substantia gelatinosa of the spinal cord was investigated in adult Sprague Dawley rats following intracutaneous injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). The different parts of the foot were found to project in a precise manner to the medial two-thirds of the substantia gelatinosa of the spinal cord segments L3-L5. The projections from the digits were arranged in a consecutive row rostrocaudally, with the most medial digit in caudal L3 and the most lateral digit in caudal L4 or rostral L5. The plantar skin was found to project both rostral and caudal to the projection of the digits. The dorsal foot skin projects lateral to the digits, neighboured by the medial edge of the foot rostrally and the lateral edge caudally. Within the projection of a particular digit, the plantar skin was found medially and the dorsal skin laterally. A certain degree of overlap for the projections from the different foot skin areas was found.