Distribution of neurons in the lateral pontine tegmentum projecting to thoracic, lumbar and sacral spinal segments in the cat.
The course of descending fibers projecting to the spinal cord and the arrangement of their parent cells located in various nuclei of the dorso-lateral pontine tegmentum were studied using the horseradish peroxidase (HRP) retrograde axonal transport technique. Retrogradely labeled neurons were found in the locus coeruleus (LC), subcoeruleus (SC), Kölliker-Fuse nucleus (KF) and in the lateral parabrachial nucleus (LPB) after HRP injections into various spinal segments. Neurons innervating the thoracic spinal cord were found to be arranged in the ventral portion of the LC and in the entire SC; their axons descended ipsilaterally. Neurons with descending axons to lumbar segments were seen mainly in the ventral portion of the LC and in the medial portion of SC. Most of their axons were also seen to descend ipsilaterally. Neurons projecting to sacral segments occurred in the entire LC and in the medial portion of the SC. Large part of descending fibers crossed the midline at the level of (or near) the termination site. Neurons of all portions of the KF and LPB projected to the thoracic spinal cord only ipsilaterally, while many descending fibers innervating the sacral segments crossed the midline.
D000818:Animals; D002415:Cats; D004525:Efferent Pathways / Q000033:anatomy & histology; D013116:Spinal Cord / Q000033:anatomy & histology*; D013681:Tegmentum Mesencephali / Q000033:anatomy & histology* / Q000166:cytology