BRAIN-STEM PROJECTIONS OF RAT LUMBAR DORSAL-ROOT GANGLIA STUDIED WITH CHOLERAGENOID CONJUGATED HORSERADISH-PEROXIDASE

Brain stem projections from each of the L1-L6 lumbar dorsal root ganglia (DRGs) were investigated in adult rats following DRG injections of choleragenoid-horseradish peroxidase. All these DRGs projected throughout the rostrocaudal extent of the gracile nucleus (Gr). Labeling from L1-L6 DRGs was transported to successively more dorsomedial areas of Gr. Investigation of the Gr projections from the DRGs revealed a somatotopic organization which was most prominent in the middle part of Gr. The cuneate nucleus showed smaller projections from all investigated DRGs. Minor projections to the internal basilar nucleus, external cuneate nucleus, medial vestibular nucleus, ventral cochlear nucleus and trigeminal sensory nuclei were also found from some of the DRGs.