Morphological evidence for newly discovered double projection spinal neurons

A novel population of spinal neurons is shown to terminate in two nuclei: the lateral cervical nucleus and the dorsal column nuclei. Nuclear yellow and Fast blue injected respectively into these nuclei are retrogradely transported to common neurons in the lumbosacral dorsal horn. The bifurcation of these neurons' axons appears to occur at the cervico-thoracic junction. These results indicate that some dorsal horn neurons transmit sensory information to two distinct nuclei. The two projections and their branching points may play a special role in neuronal communication.