Long ascending projections from substantia gelatinosa Rolandi and the subjacent dorsal horn in the rat.

Small neurons of the substantia gelatinosa Rolandi and the subjacent dorsal horn of the spinal cord have been thought to exert a direct modulatory effect only on neurons located within a distance of a few spinal segemnts. By using the technique of retorograde transport of horseradish peroxidase, however, it has been found that in the rat a significant number of these cells, particularly those of the subjacent dorsal horn, ascend many spinal segments to the lateral cervical nucleus and to the lower brainstem. These data provide an anatomic basis for a role of substantia gelatinosa Rolandi and subjacent dorsal horn cells in madulating or contributing to sensory information transmission not only in nearby segments but in far distant structures.