Funicular location of ascending axons of lamina I cells in the cat spinal cord.

The laminar distribution of spinal cord neurons projecting suprasegmentally through different funiculi was determined in the cat using horseradish peroxidase (HRP) injections combined with selective spinal cord lesions. The lesions were designed to limit the caudal transport of HRP to either the ventral funiculi or the dorsolateral funiculus. HRP injections in the ventromedial or ventrolateral funiculi resulted in labeling primarily within laminae IV-VIII and a virtual lack of labeling within lamina I. When the dorsolateral funiculus was injected, 20-25% of all labeled cells were located in lamina I, bilaterally. These results demonstrate that the ascending lamina I projections are through the dorsolateral funiculus.