The descending substance P projections from the ventral medulla were studied in the rat. Electrolytic lesions which included the nucleus interfascicularis hypoglossi decrease the substance P-like immunoreactivity (SP-I) in both the intermediolateral cell column and the ventral horn of the spinal cord. Lesions of other ventral medullary areas and midbrain hemisections did not change spinal cord SP-I levels. Intracerebroventricular administration of the serotonin neurotoxin, 5,7-dihydroxytryptamine, reduced the SP-I content of the ventral horn but not of the intermediolateral cell colum.
- intermediolateral cell column
- raphe nuclei
- substance P
- ventral horn of the spinal cord
- ventral medulla