Spinal projections of brainstem respiratory related neurons in the cat as revealed by retrograde fluorescent markers

Abstract

By means of retrograde axonal transport of fluorescent tracers, connections between brainstem respiratory related regions and the spinal cord has been studied in the cat.Neurons at the pneumotaxic center project bilaterally (90% ipsi-, 10% contra-) to cervical and lumbar spinal cord and ipsilaterally to thoracic levels.The ventrolateral nucleus of the tractus solitarius project mainly contralaterally (85%) to cervical levels and only contralaterally to thoracic levels; no efferent projections were found to lumbar levels.The ventral respiratory group showed a great number of neurons projecting to the spinal cord especially from the nucleus retroambiguus.Both nuclei, ambiguus and retroambiguus, project mainly contralaterally (70%) to the spinal cord.The Bötzinger complex showed rather scarce bilateral projections to cervical and only ipsilateral projections to lower cervical, thoracic and lumber levels.