The axons of raphespinal sympathoinhibitory neurons branch in the cervical spinal cord.

This study shows that the axons of some raphespinal sympathoinhibitory neurons projecting to the third thoracic spinal segment emit branches in the third-fourth cervical spinal segments of cats. This was demonstrated by using time-controlled collision of neuronal action potentials initiated by stimuli applied at these spinal levels. Antidromic mapping revealed that the cervical branches of these neurons likely terminated in Rexed's lamina VII. In contrast to these raphe neurons, the axons of ventrolateral medullospinal sympathoexcitatory neurons did not emit cervical branches.