BRAIN-STEM NEURONS WITH PROJECTING AXONS TO BOTH PHRENIC AND ABDOMINAL MOTOR NUCLEI - A DOUBLE FLUORESCENT LABELING STUDY IN THE CAT

The distribution of retrogradely doubly labeled brainstem neurons were analyzed in the cat after injection of two different fluorescent mark ers into the phrenic and abdominal motor nuclei. Diamidino Yellow (DY) was first injected either ipsilaterally or bilaterally into the ventr al horn of lumbar spinal cord, and then Fast Blue (FB) into the right ventral horn of cervical spinal cord. Doubly labeled neurons were main ly found in the caudal ventrolateral medulla (retroambiguus region), i n the dorsomedial and dorsolateral regions of the nucleus of the tract us solitarius (NTS) and in the raphe nuclei. In addition, doubly label ed neurons were found in the parabrachial and Kolliker-Fuse nuclei. Ou r results give anatomical evidence that pontine and medullary neurons are the source of a common pathway to both phrenic and abdominal motor nuclei. These neurons might be involved in strain efforts for expulsi on such as vomiting or defecation.