Funicular location of the ascending axons of neurons adjacent to the spinal cord central canal in the rat.

Neurons adjacent to the central canal in the rat spinal cord were retrogradely labeled bilaterally after injection of horseradish peroxidase into the bulbar reticular formation. Lesions restricted to parts of the ventral lateral funiculus in thoracic or high lumbar segments on the side ipsilateral to the injections produced significant bilateral reductions in labeling. Lesions that included the entire ipsilateral ventral lateral funiculus greatly reduced the number of labeled neurons surrounding the central canal caudal to the lesion. Lesions of either the dorsal lateral funiculus, or midline lesions encompassing both the dorsal and ventral columns had no significant effect on labeling. Spinoreticular tract neurons on both sides of the central canal issue axons that ascend in the ventral lateral funiculus of the side ipsilateral to their termination.