Localization of the phrenic nucleus in the rat: a HRP study.

The localization of the phrenic nucleus in the rat spinal cord was studied with the horseradish peroxidase (HRP) method. After injection of HRP into the hemidiaphragm, labeled neurons were localized in a distinct nucleus between the ventromedial and ventrolateral cell groups of the ventral horn, with a longitudinal extension from the rostral 3rd to 5th cervical segments. Labeled neurons were oval or round in shape, medium-sized and tightly clustered. Labeled neurons were found in a well-defined cell column parallel to the longitudinal axis of the cervical spinal cord in frontal sections.